Category Archives: Quantum Physics

Special relativity could open the door to ultra-secure ATM machines.

It's Monday morning and you're headed to grab an espresso from a corner cafe. Upon entering, you run into the dreaded "cash only" sign. "No problem," you think, wandering to the nearest ATM. You arrive at the machine, slip out your debit card, insert its worn chip and cup your hands into mini-shields while punching in your secret PIN.

During the process, however, sly thieves might have seen past your humble security measures. They may have even preemptively hacked the cash machine to collect your code. To withdraw money for coffee, you've actually risked theft.

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Could there be a safer way to do this? A team of researchers hailing from Canada and Switzerland are determined to find out. They published a blueprint in the journal Natureearlier this month that detailed an ultra-secure cash machine that would completely reinvent the system.

"The assumption of trusting the device when you are doing anything related to identification is kind of a problem, at least at the fundamental level," said Sbastien Designolle, a physicist at the University of Geneva and co-author of the study.

"Drop all assumptions" is the motto he and fellow researchers abided by while coming up with a more secure mechanism to retrieve cash.

Anchoring their far-fetched idea with physicist Albert Einstein's theory of special relativity, they propose replacing the PIN system with what's called a zero-knowledge proof.

Here's how it works.

Remember brain teasers? Zero-knowledge proofs are like a grownup version of such mind games. In cryptography, which is the study of secure communication, they're a method by which party A proves to party B that they know something. The catch is, party A, the prover, can't reveal the information they know to party B, the verifier.

But there's a way for party A to get around the caveat.

Suppose you have a friend named Jones who can only see in black and white, but you can see in color. Your objective is to prove to Jones you can, in fact, see color. If you were to use a zero-knowledge proof, it might go something like this:

Jones holds a red card and a blue card before you. Then, behind his back, he either swaps them or doesn't swap them. Laying them out in front of you again, he asks, "Did I swap them?"

The game could be repeated a hundred times, and you'll always have the correct answer because you can see the colors. After many iterations, Jones would eventually say, "Alright, I believe you. You can see color." At that point, you've shown him your color-identifying ability without revealing the colors you see.

"In our study," explained Designolle, "the proof is the three-colorability of a graph."

Albert Einstein's theory of special relativity could get a new practical application.

There's some lore behind the idea. Three-colorability is a notoriously difficult mathematical problemthat theorists have studied for years. It posits the question: How can you color an enormous map of shapes with three shades such that the same colors never touch?

This wouldn't be like world maps we're used to. It'd be so huge that humans need technology to comprehend it, but even with such help, Designolle said it would take years to find a three-colorability solution.

Taking the concept to ATMs, he suggests giving everyone a device holding a uniquely colorized map with a preprogrammed three-colorability solution. To withdraw cash, you'd plug the device into an external outlet on the ATM, the verifier in this case.

The machine would query your device, or prover, with hundreds of thousands of questions regarding sections of your map's colors. Despite the complexity of three-colorability, your device would immediately answer because it's been preprogrammed.

Further, because every round of queries is randomized, even if the verifier asks about different edges, the ATM would never receive enough information to know the full map, Designolle explained, "which is the crucial point."

Eventually, like in the situation with Jones, the ATM will verify your identity and roll out your cash because of your device's consistently correct answers -- like the way Jones said, "Alright, I believe you. You can see color." Ta-da.

The invention seems solid -- to me, at least. But Designolle and his team aimed to drop all assumptions. They still didn't completely trust the security of the three-color map system.

Hypothetically, they argue, someone could record your device's sparse answers about its map and attempt to reverse calculate the full picture, enabling them to fake your identity.

"Those functions that you can perform in one direction are very difficult, but not impossible, to compute in the other direction," Designolle said.

For example, if you multiply two prime numbers and get a very big number, it's difficult to go back to the elementary numbers. But that doesn't bar it from being done. The same applies to three-colorability.

So, how can we take these machines to a level of unconditional security? Designolle thought, well, what about invoking two devices?

"The idea behind this is precisely the same as a policeman investigating and asking two separate suspects [questions] in different rooms, so that they can't communicate," Designolle said. "If they are telling the same version of the story, then it's a good hint they actually are telling the truth."

Two ATMs, two devices -- ultimate safety?

Back to the cash machine.

With two devices, you'd divide yourself into two provers, like the two suspects. Then, two verifiers, ATMs, will simultaneously ask its respective prover the usual three-colorability questions.

Yes, you would have to plug two separate devices into two separate ATMs. At present, the researchers say the system works with the ATMs standing 60 meters (about 196 feet) apart. But they say they can get it down to a meter, or about 3 feet. It sounds overly complicated, but remember, the purpose of the experiment is to illustrate what an unconditionally secure cash machine mechanism might look like. It's theoretical -- for now, at least.

If each prover appears to hold the same, incalculable knowledge, it'd be safe to say that your identity is verified.

And like the criminal suspects, the devices wouldn't be able to communicate with each other. Any potential hacker would need to reverse calculate not one, but two, complex maps at the exact same time, an exceptionally challenging -- if not impossible -- task.

Here's the moment you've been waiting for -- where Einstein comes in. The reason these devices wouldn't be able to communicate is they'd be bound by Einstein's theory of special relativity.

Einstein's theory of special relativity beautifully marries the realms of space and time. But more importantly for Designolle's team, it also leads to constraints on how fast information travels.

"With special relativity," Designolle said, "it seems quite reasonable to believe in this not computational but physical assumption ... that information cannot go faster than the speed of light."

As long as the two ATMs ask their respective plugged-in, map-filled devices questions quickly enough for lags to always remain shorter than the time needed to transfer information -- restricted by the speed of light -- we'd guard against the possibility of the devices talking to each other.

In a sense, the provers couldn't check their "alibis" to fake an identity.

There's just one, final issue. These relativistic constraints aren't so airtight when it comes to nonconventional physics. Enter quantum computing.

Light works differently in the quantum world. Quantum mechanics allows for a fascinating principle called quantum entanglement. Put simply, when two quantum particles -- namely, light particles -- are entangled, they can instantaneously communicate.

It's not even a matter of how fast the information travels. It's immediate. If particle A holds knowledge of something, you can be absolutely sure particle B already knows it too.

IBM's quantum computer

"Suppose that I do not have the coloring of a graph, but I want to pretend that I do," Designolle said, referring to a potential hacker. "I could come up with a procedure using quantum entanglement between the two chips to answer the questions correctly. In a way, I can cheat."

While Designolle's team believes their mechanism should be able to guarantee safety from quantum hackers, they're not sure. However, they're currently pondering whether the protocol could itself use quantum provers instead of standard devices.

And if you've gotten this far, you might be wondering exactly how theoretical these ultra-secure ATMs are. Is it even possible to bring them into reality?

Right now, Designolle said, the main issue is cost. In order to create the devices needed for the mechanism, the chips can't be the same type we find on our debit cards today. They will have to be extremely powerful, which means they'll likely be very expensive. One idea he has is to invoke the system for large companies that trade secure information and can afford the pricey chips.

That would actually make the relativistic constraints looser because there would be a greater distance between each party's device and the verifying "cash machine," so light would take longer to travel. This means there'd be more room for lags before hackers can penetrate the system.

But aside from the realistic applications, Designolle said, "On a personal note, it was really interesting just to see that sometimes something very simple is actually hard to come up with. ... At some point, yes, this occurred, but it was not very clear from the beginning that it would be so simple in the end."

Excerpt from:

Einstein's theory of special relativity could create unhackable ATMs - CNET

November 15, 2021• Physics 14, 159

Researchers have produced an optical lattice of atoms that can generate sound, a previously unachieved feat.

B. Lev/Stanford University

B. Lev/Stanford University

The movements and interactions of ultracold atoms, trapped by lasers in a periodic lattice structure, provides a popular analog for the behaviors of electrons in crystalline solids (see Coming Soon: Cold Atoms Impersonate Superconductors). But the ultracold atomic system lacks a key feature of solid materialsthe lattice on which the atoms sit cant vibrate or deform. Studies that rely on the analogous optical lattice fail to capture the impact on the system of natural vibrations intrinsic to condensed-matter systems. Now, Benjamin Lev of Stanford University and colleagues demonstrate a way to add that motion to the lattice. Lev says that the advance could enable researchers to better replicate and explore the behavior of condensed-matter systems using cold atoms, as well as to create novel forms of quantum matter.

Optical lattices are static, rigid structures by design. Traditionally made by interfering laser beams in free space, they can also be produced in optical cavities, which confine standing light waves. The result is a checkerboard light field comprising high- and low-intensity regions. An atom in the cavity that wanders into a high-intensity square when this field is turned on experiences an attractive force that draws it to the center of that square and traps it in place. The optical cavities used in such experiments are known as single-mode cavities, meaning that only one specific wavelength can be confined as a standing wave. As a result, any lattice made in such a cavity has a fixed and rigid structure. The spacing between the nodes [of the lattice] cant bend or vibrate, Lev says. In other words, the lattice is silent.

To generate sound, an optical lattice needs flexibility. Predictions suggest that creating the lattice in a multimode optical cavity may introduce that flexibility. Multimode cavities, as their name implies, support many different light patterns, all made with the same frequency of light. Creating lattices using different patterns adds compliance to the lattice. The cavity we use provides a lot more flexibility in terms of the shape of the light that bounces back and forth between the mirrors, Lev says. Its as if instead of just being allowed to make a single wave in a trough of water, you can now splash about to make any sort of wave pattern. That means that if the atoms want to change their positions a little bit, the light can accommodate those changes without much difficulty, he adds.

Multimode cavities exist but have rarely been used in cold-atom experiments. Now, demonstrating this new application, Lev and his colleagues confined 100,000 ultracold rubidium atoms inside a multimode cavity that consists of two curved mirrors, each with radius of curvature equal to the length of the cavity.

The teams calculations show that photons that resonate in such a cavity can, when scattering off the trapped atoms, mediate interactions between those atoms through an exchange of photons. This exchange induces a flexing of the lattice. Theory shows that this flexing mimics the movement of atoms in solids caused by quantized sound waves known as phonons. By observing how the system responded to an energy perturbation, which here they initiated using patterned light, the team was able to both confirm that the predicted phonons appeared and measure their properties. The speed of sound in the lattice is related to the phonons presence.

The team found the speed of sound in their rubidium-atom lattice to be 16 cm/s, about double the speed of a giant tortoise. If it were possible to put your ear to the atoms, you would hear them vibrate at around 1 kHz, Lev says. Of course, you cant do that because the system is in a vacuum chamber and its really tiny, he jokes. But we can take pictures of the atoms.

Images taken using the cavitywhich also works as a quantum gas microscopeshowed that the trapped rubidium atoms formed a vibrating supersolid state, a phase of matter that simultaneously displays crystalline order and superfluid flow.

The demonstration is an experimental breakthrough, says Victor Galitski, a physicist at the University of Maryland. It both opens up new avenues for quantum simulation of previously inaccessible phenomena in solid-state materials and potentially may give rise to [researchers uncovering] completely new physics with no analog elsewhere. Elizabeth Goldschmidt, a physicist at the University of Illinois Urbana-Champaign, echoes that opinion. She notes that the ability to turn on phonons in ultracold atoms systems adds a new feature to the toolkit for these experiments. The role of phonons in real crystals is both central to many of their properties and extremely difficult to model in detail. Thus, studying phonons in a much simpler system like this can elucidate new and exciting physics that is highly relevant to many real materials and systems, she says.

Lev agrees. By tweaking the system, he thinks that the approach might be able to create states that emulate the behavior of exotic solid-state superconductors. The system could also create other states of matter that have no direct condensed-matter counterpart, such as a predicted stripy Bose-Einstein condensate that resembles a type of liquid crystal. Lev and his colleagues are also working on using the photon-atom interactions to create spin glasses, or collections of spins that align randomly in a solid. Those structures are promising tools for creating neuromorphic computers, which essentially act like artificial brains by operating in a manner that mimics how the brain sends, receives, and processes signals. I think that what we have created is this really fertile experimental tool that gives us a brand-new way to shape how quantum particles can interact and organize themselves, Lev says. It opens up new directions for accessing nonequilibrium quantum matter, a realm that deserves much more exploration.

Katherine Wright

Katherine Wright is the Deputy Editor of Physics.

Here is the original post:

Physics - A Humming Lattice of Cold Atoms - Physics

Pic: Edex Live

It is not everyday that great theories are created by people working as a clerk at a patent office. But then Albert Einstein was not your everyday person either. You know the guy who came up with the theory of relativity. But it was not all that he contributed to physics. It was on this day back in 1908, that he presented his quantum theory of light. The theory basically stated that both, Newton's particle theory and the wave theory hold true for light. This effectively led to the birth of the field in physics called quantum physics. The theory explained that lights operated at a constant speed despite space and time and that it was composed of tiny particles which gave it a wavelike characteristic. This was the beginning of what led him to the discovery of the law of the photoelectric effect, which later earned him a Nobel Prize.

The day is also memorable for being the World Diabetes Day. The day falls on the birthday of Frederick Banting, who along withCharles BestandJohn James Rickard Macleodconceived the idea which later led to the synthesis of insulin. Led by the International Diabetes Federation, each World Diabetes Day focuses on a specific theme related to the disease. It was first observed in 1991 by IDF and the World Health Organization. It became an official United Nations Day in 2006. The theme for WDD for 2021-23 isAccess to Diabetes Care If Not Now, When?Today more than 460 million are living with diabetes and the campaign seeks to draw people's attention towards it.

Read this article:

What happened on November 14: Einstein explained light's nature and a day to raise awareness regarding diabetes - EdexLive

Significance

Cuticulosomes are subcellular structures located within the inner ear hair cells of a variety of avian species with potential relevance to magnetoreception. Here we apply quantum magnetic microscopy to image the magnetic properties of individual iron cuticulosomes within tissue samples. The magnetic susceptibility of the cuticulosomes was determined by characterizing the stray magnetic field strength as a function of applied magnetic field in two distinct locations of the pigeon inner ear. The measured susceptibilities do not support the particle model of magnetoreception, suggesting the physiological relevance of cuticulosomes lies in iron storage or stabilization of stereocilia. The quantum magnetic imaging method can be applied across a variety of biological systems providing an effective tool to screen for magnetic particlebased magnetoreceptors.

The ability of pigeons to sense geomagnetic fields has been conclusively established despite a notable lack of determination of the underlying biophysical mechanisms. Quasi-spherical iron organelles previously termed cuticulosomes in the cochlea of pigeons have potential relevance to magnetoreception due to their location and iron composition; however, data regarding the magnetic susceptibility of these structures are currently limited. Here quantum magnetic imaging techniques are applied to characterize the magnetic properties of individual iron cuticulosomes in situ. The stray magnetic fields emanating from cuticulosomes are mapped and compared to a detailed analytical model to provide an estimate of the magnetic susceptibility of the individual particles. The images reveal the presence of superparamagnetic and ferrimagnetic domains within individual cuticulosomes and magnetic susceptibilities within the range 0.029 to 0.22. These results provide insights into the elusive physiological roles of cuticulosomes. The susceptibilities measured are not consistent with a torque-based model of magnetoreception, placing iron storage and stereocilia stabilization as the two leading putative cuticulosome functions. This work establishes quantum magnetic imaging as an important tool to complement the existing array of techniques used to screen for potential magnetic particlebased magnetoreceptor candidates.

Magnetoreception in diverse avian species including pigeons has been well established through behavioral studies (1); however, the biophysical mechanisms that underlie the sense are yet to be determined (2). The models proposed to date are based on three biophysical concepts: 1) a torque-based ferrimagnetic particle model (3), 2) the formation of radical pairs (4), and 3) electromagnetic induction (5). Magnetoreceptor candidates based on these models exist in the retina (4) and the inner ear (6). Analysis of the immediate early gene C-FOS has implicated the vestibular system in the magnetic sense, which in turn led to the discovery of cuticulosomes (7). These spherical structures reside in the actin-rich cuticular plate of hair cells in the lagena, basilar papilla, saccule, and utricle of the pigeon inner ear (6). Cuticulosomes have been studied extensively using high-resolution electron microscopy to characterize their size and morphology (6). The available evidence indicates that they are primarily composed of the iron oxide ferrihydrite, are 300 to 600 nm in diameter, and are present in 2 to 6% of vestibular hair cells and 25% of acoustic hair cells located in the basilar papilla. The function of these organelles is unknown, but it has been proposed that they either act as a store for excess iron, stabilize stereocilia, or mediate magnetoreception.

The acquisition of empirical magnetic data from cuticulosomes poses a significant technological challenge due to the small size and magnetization of these objects (8). The spatial resolution of high-temperature scanning superconducting quantum interference devices is insufficient to image single magnetic structures of this size, despite their high magnetic sensitivity (9). Spatial resolutions on nanometer scales can be achieved using magnetic force microscopy and scanning tunneling microscopes. These techniques are of limited utility to the current application due to long acquisition times, limited measurement throughput, and in some cases cryogenic and high-vacuum environments (10, 11). Elemental analysis has been undertaken using X-ray fluorescence microscopy (12) and inductively coupled plasma mass spectrometry (13). However, direct measurements of the magnetic properties of these particles are not provided through the application of these technologies.

Magnetic field imaging was performed using a custom inverted wide-field microscope. Optical excitation at 532 nm was used to excite the nitrogen-vacancy (NV) centers in the diamond magnetic sensing chip. The resulting NV fluorescence was captured, filtered, and imaged onto a sensitive scientific complementary metal-oxide-semiconductor (sCMOS) camera. A microwave antenna was used to apply the spin control sequences required to infer local magnetic fields via optically detected magnetic resonance (ODMR), as shown in Fig.1A. Thin tissue samples from the lagena and basilar papilla in the cochlear duct of adult pigeons were prepared, as illustrated in Fig.1B. The samples were embedded in epoxy resin, and regions of interest were microtomed to a thickness of 500 nm (Materials and Methods). The sections were then transferred to the diamond on a drop of bidistilled water and air dried under a microscope.

Overview of the design of the experiment. (A) The biological sample is affixed to the top of a diamond imaging chip containing a layer of NVs. The imaging chip sits on top of a glass coverslip onto which a gold microwave antenna is printed. The NV centers are addressed using a 532-nm excitation wave, and their fluorescence is captured using an sCMOS camera. A permanent magnet on a mobile mount is used to control the applied magnetic field at the NV layer. (B) Details of the biological sample of interest. Thin sections are taken containing inner ear hair cells from the lagena and basilar papilla of pigeons. The diagrams of the pigeon inner ear and cochlea show the region of the pigeon anatomy of interest in these experiments. The section displayed contains structures which are stained using Prussian blue and is representative of the sections and structures of interest in this study. The sections analyzed were not subject to Prussian blue staining. (C) Details of the diamond imaging chips used. The NV centers fluoresce red when optically addressed with the 532-nm excitation wave. A nonfluorescent decay pathway linked to the +1 spin sublevels of the excited state manifold results in a reduced NV fluorescence. Additionally, the nonfluorescent decay pathway populates the 0 sublevel of the ground state manifold. NV systems in the 0 sublevel can be driven into the other sublevels through the application of a resonant microwave field, . The combination of these properties allows spin state control and readout. The positions of the 1 and +1 spin sublevels split in frequency space as a magnetic field is applied along the axis of the NV system. (D) Film reel showing magnetic field maps of a magnetic particle with increasing applied magnetic field strengths. The images are produced by measuring the fluorescence of the NV centers at each pixel and sweeping the microwave frequency. Where the frequency is resonant with the 0 to 1 transition, a dip in the fluorescence is measured, and from the resonant frequency the local magnetic field strength can be inferred.

The NV defect in diamond consists of a substitutional nitrogen atom with an adjacent lattice vacancy aligned along one of four diamond crystallographic axes. Under 532-nm optical excitation this defect can be initialized into the 0 spin sublevel. The spin state can be read out optically from the fluorescence intensity difference between the 0 and 1 sublevels as illustrated in Fig.1C. The positions of these energy levels can be determined by monitoring the NV fluorescence intensity while sweeping a microwave field through the respective 0 to 1 transitions. The resulting ODMR spectrum can then be acquired from each imaging pixel of the quantum magnetic microscope. Static magnetic fields aligned with an NV axis Zeeman split the 1 and 1 states with a gyromagnetic ratio of = 2.8 MHzG 1. The Zeeman splitting can, therefore, be used to report the local magnetic field projected along the NV axis at each imaging pixel, as shown in Fig.1D. Here an ODMR protocol (14) is applied to image the stray static magnetic fields from individual cuticulosomes under a range of applied magnetic field strengths.

With the samples mounted, a series of ODMR images were recorded to screen for magnetic signals present in the hair cells in the lagena and basilar papilla. The diamond sensing chips were able to hold three tissue sections allowing for 300 individual hair cells from the lagena or 80 individual hair cells from the basilar papilla to be scanned on a single sensor chip. The field of view of the microscope was 150 m2, and the magnetic image resolution was 450 50 nm. The local magnetic field projection along the NV axis was determined by monitoring the ODMR peak separation (15). The initial screening process involves magnetizing the cuticulosomes via application of a 1,400 G applied field. The initial acquisition times for each 150 m2 field of view was between 30 and 60 min. Any magnetic features observed in the initial screen were then targeted for detailed analysis.

To provide insight into the magnetic susceptibility of iron cuticulosomes, magnetic images were taken under a range of applied fields, B0, ranging from 100 to 1,900 G. Cell surveys of the lagena and basilar papilla, as shown in Fig.2A, identified approximately four and six iron cuticulosomes from 300 and 80 hair cells, respectively. The resulting stray magnetic field profiles from the individual cuticulosomes present in the lagena and basilar papilla are shown in Figs. 2B and 3, respectively. The image acquisition details are outlined in Materials and Methods. Differences in the observed stray magnetic spatial profiles can be accounted for by the height between the NV sensing layer and the iron cuticulosomes in the tissue and are discussed further in SI Appendix.

Cuticulosome measurements and the anatomical origins of the cuticulosomes investigated. (A) Schematics and bright-field images showing the orientation of the sections taken, the location of the lagena within the inner ear, and the components of interest within the sections. The second bright-field image is an enlargement of the region indicated by the black rectangle in the first. The black arrow indicates the location of a cuticulosome within the tissue sample. (Scale bar, 5 m.) (B) ODMR images showing the stray magnetic field imaged below cuticulosomes found in the lagena. The applied magnetic field increases from left to right from 200 to 1,400 G with each row representing a different particle. Cuticulosome L1 is the same cuticulosome shown in A. (Scale bar, 5 m.)

ODMR images showing the stray magnetic field imaged below cuticulosomes found in the basilar papilla. The applied magnetic field increases from left to right from 200 to 1,400 G with each row representing a different particle. (Scale bar, 5 m.)

To quantify the stray magnetic field strengths, a line cut was taken to infer the peak to peak magnitude of the measured field BNV as shown in Fig.4 A and B. This procedure was repeated over the range of applied fields to study the relationship between the stray field strength, BNV, and the applied field, B0, as shown in Fig.4C. The gradient of the stray field vs. the applied field will here be referred to as and is proportional to the magnetic susceptibility. The average values of determined for cuticulosomes in the lagena and basilar papilla were (3.51.5)104 and (2.30.9)104, respectively. The value for measured for each individual particle is documented in SI Appendix. To gain further insight into the magnetic images an analytical model is developed and applied to extract estimates of the magnetic susceptibility of the cuticulosomes as described in the section below.

Calculation of the magnetic susceptibility of a cuticulosome via the comparison of stray magnetic field images with a detailed theoretical model. (A) Representative image of the stray magnetic field as inferred through the analysis of ODMR images. The axis width is 13 m. (B) Line cut through the center of the stray magnetic field measured in A. The peak to peak size of the double Gaussian fits to the data provides a metric for of the strength of the signal. (C) Plot of the strength of the signal as a function of the applied magnetic field, B0. Error bars are calculated as the SD of the background. (D) Simulated stray magnetic field. The axis width is 13 m. (E) Simulated effective magnetic field accounting for the integrated NV response and the optical diffraction limit. The axis width is 13 m. (F) Simulation presenting the gradient of the signal strength as a function of applied field for a range of particle heights and magnetic susceptibilities. The green line represents the response produced by a sphere of ferrihydrite of the same diameter. The solid red line represents the points which result in the same NV response as the average of the experimentally measured NV responses. The red dashed lines represent the average experimentally measured NV response plus or minus 1 SD. The blacked out region of the map represents regions where an increased microwave frequency sweep range would be required to extract the resonant frequencies from all pixels of the simulated ODMR images.

The magnetic field model for the iron cuticulosomes takes into account the externally applied magnetic field, magnetic susceptibility, easy axis orientation, and cuticulosome geometry. The cuticulosomes are modeled as a large number of magnetic dipoles, producing a field,Bc(r)=vVB04(3r(m^r)r5m^r3),[1]where B0 is the applied magnetic field, v is the volume magnetic susceptibility of the cuticulosome, V is the volume of the cuticulosome, and m^ is the direction of magnetization of the cuticulosome. The Zeeman splitting induced from an individual NV center at a position r relative to the center of the cuticulosome is calculated from the projection of Bc along the axis of that NV center and will be referred to as Bz from here on.

Fig.4D shows a simulation of Bz for the measured cuticulosome in Fig.4A. The simulation was performed with a volume susceptibility of 0.053, a cuticulosome diameter of 365 nm, and a height of 207.5 nm, with an easy axis aligned with the applied magnetic field (1,400 G). Crystalline magnetic materials have a direction in which an applied magnetic field will more readily magnetize the material, with that direction being known as the easy axis of the material (16). The presence of an easy axis occurs due to the combination of magnetocrystalline effects, shape anisotropy, and surface effects creating energetically preferred spin alignments. The model assumes a cuticulosome geometry with an aspect ratio of 1. This is informed by electron microscopy studies conducted by Lauwers et al. (6). The image presented in Fig.4D was generated for the case where the easy axis and applied field are aligned. A packing ratio of 0.7 was assumed for the efficiency of the infilling of the cuticulosome volume with magnetic material (17). The resolution of the image is set to be 5 nm.

The theoretical model developed here also considers physics behind the quantum magnetic imaging system to produce an effective stray magnetic field which accounts for the NV dynamic range, implant depth, cuticulosome height, and optical imaging resolution (18). See SI Appendix for more details. The resulting simulated effective stray magnetic field, as shown in Fig.4E, can then be compared with the measured magnetic field profiles. There is excellent qualitative agreement between the two profiles. An upper bound on the variation that would result from magnetic anisotropy was determined by simulating the response from a large number cuticulosomes with uniaxial magnetization. Easy axis directions were generated using a Monte Carlo simulation. Apart from the easy axis direction, all parameters of the simulations were identical to each other and to the cuticulosome simulated in Fig.4 D and E. By comparing the SD of the stray magnetic field amplitudes to their mean for 300 instances of the Monte Carlo simulation, a relative error in of 0.25 was determined.

Leveraging the theoretical model allows us to place bounds on the magnetic susceptibility based on the experimental data. Due to the number of free parameters in the theoretical model it is not possible to calculate the magnetic susceptibility directly as a function of . However, by repeating the simulations over the physically realistic range of cuticulosome radii and heights it is possible to place bounds on the susceptibility of individual particles. is calculated for each parameter set, producing a finite range of magnetic susceptibilities capable of reproducing the experimental data. This method is presented in Fig.4F where a representative particle diameter of 365 nm is chosen, in line with an analysis of cuticulosomes performed via electron microscopy (6), and where the cuticulosome height is swept over the tissue sample thickness. Contour lines depicting the combinations of height, magnetic susceptibility, magnetic anisotropy, and radius which are consistent with experimental data are drawn to impose limits on the magnetic susceptibility of cuticulosomes. The lower and upper bounds on the magnetic susceptibilities inferred through these simulations are 0.029 and 0.22, respectively. These susceptibilities are an order of magnitude less than those reported for magnetite (19), suggesting that the iron cuticulosomes are composed of composite iron biominerals with magnetic susceptibilities more consistent with ferrihydrite. These values can be compared to the magnetic susceptibilities of known iron oxide species as listed in Table 1.

Magnetic susceptibility ranges and mass densities of a variety of iron oxide species

To understand if the magnetic susceptibilities measured are consistent with the ferrimagnetic particlebased model, the force required to mediate a magnetoreceptive response is compared to the force produced by cuticulosomes in geomagnetic fields. The force required for the gating of mechanoelectrical transduction channels is assumed to be comparable to the gating force measured in saccular hair cells of a bullfrog, which is (2.90.6)1013 N (20). The upper bounds of the forces capable of being exerted by cuticulosomes are calculated to determine the feasibility of cuticulosomes acting as mediators of magnetic field information. The calculations to determine the upper bounds are presented in Materials and Methods and produce a maximum value of 1018 N which is five orders of magnitude too small to gate known mechanoelectrical channels. As such, the data obtained from the analysis do not support the proposal that cuticulosomes act as particle-based mediators of magnetic fields and complement theoretical treatments of the behavior of cuticulosomes in geomagnetic fields (19).

The results reported herein support the claim that cuticulosomes contain several iron oxide minerals (21). The magnetic susceptibilities measured are not consistent with either the modeling of cuticulosomes as solid spheres of magnetite or as solid spheres of ferrihydrite. Low-temperature magnetic studies on horse spleen ferritin have provided evidence of mixed mineral phases of ferrihydrite and magnetite/maghemite (22). The measurement of mixed mineral phases measured in horse spleen ferritin provides the motivation to further analyze the mixed mineral composition observed within cuticulosomes. Information regarding the mineral composition of cuticulosomes was gleaned using stray magnetic field imaging to quantify their magnetic susceptibilities. Additional information can be obtained by studying the superparamagnetism of cuticulosomes. This was undertaken through quantum relaxometry and is discussed in the next section.

The magnetic domains associated with superparamagetic materials are known to fluctuate with a frequency spectrum dependent on the volume of the magnetic material, anisotropy energy barrier, mineral composition, and temperature. For iron biominerals such as ferrihydrite, this frequency spectrum can range between several hundred MHz and tens of GHz (14). These magnetic fluctuations can act as magnetic noise sources when brought sufficiently close (typically < 100 nm) to NV centers in diamond. By using the same wide-field microscope and monitoring the spin relaxation rate (1/T1) of the NV centers across the full field of view (Materials and Methods), we can detect and map the fluctuating magnetic fields signals directly, in a technique termed quantum relaxation microscopy (QRM) (2325). For completeness we applied QRM to image each of the iron cuticulosomes identified in Figs. 2 and 3; see SI Appendix for more information.

Two out of the 10 cuticulosomes studied show a clear change in T1 rate. Further work is required to understand whether the low percentage of cuticulosomes reporting superparamagnetic domains is statistically significant or whether the sample preparation and thickness limits T1 detection events. Regardless of the statistical significance of the number of detection events, the successful detection of fluctuating magnetic signals from individual cuticulosomes indicates that the particles are composed of both superparamagnetic and ferrimagnetic domains. It is likely that cuticulosomes may contain magnetic granules with a range of sizes and morphologies with some particles acting as superparamagnets while others act as ferrimagnets. A similar effect has been observed in clusters of synthetic maghemite nanoparticles with diameters in the 5 to 50 nm range (26). Our results highlight the nonuniformity in the magnetic properties of these materials prompting further investigation into the physiological significance of these organelles.

Here we applied wide-field quantum magnetic microscopy in two separate magnetic imaging modalities to characterize the magnetic properties of individual cuticulosomes in vestibular and acoustic hair cells of pigeons. Magnetic images were captured from 500-nm-thick sections of tissue taken from two distinct locations within the cochlear duct. ODMR microscopy was used to image the stray magnetic field from individual cuticulosomes. The stray magnetic field response to an applied magnetic field was compared to a detailed analytical model to determine the magnetic susceptibility of cuticulosomes. The magnetic susceptibilities measured to be 0.12 0.05 indicate that cuticulosomes do not have sufficient magnetization to act as a particle-based magnetoreceptor. This does not discount the other proposed physiological roles of cuticulosomes, namely, that they act as mechanical stabilizers of stereocilia or as iron stores. The magnetic susceptibility of cuticulosomes lies between the magnetic susceptibility of ferrihydrite and magnetite, motivating further study of their mineral components. With this in mind, quantum relaxometry was applied to probe the superparamagnetic components of these iron organelles. Two of the 10 organelles studied exhibited superparamagnetic properties suggesting the presence of multiple iron oxide minerals within individual cuticulosomes. Importantly, the magnetic images can be correlated to specific anatomical locations, mitigating the risk of false positives from magnetic contamination. This demonstrates the utility of quantum magnetic imaging as a means to screen for similarly small-scale magnetoreceptor candidates within biological samples. Given the simplicity of the sample preparation and imaging technique, future work will focus on applying this technology to a host of biological systems with preidentified magnetic particlebased magnetoreceptor candidates to further understand the role biogenic iron plays in animal physiology.

Adult pigeons (Austria cohort) were killed by CO2 asphyxiation and immediately intracardially perfused with 40 C 0.9% NaCl supplemented with 20 U/L heparin followed by a mixture of ice-cold 2% paraformaldehyde (PFA) and 2.5% glutaraldehyde (GA) in phosphate-buffered saline (PBS, pH 7.4). The inner ear was dissected and postfixed in 2%PFA/2.5%GA at 4 C overnight. To facilitate the penetration of the fixatives, the oval window and the semicircular canals were cut open. To limit contamination, all preparations were made with acid-washed (1% HCl) iron-free titanium and ceramic tools. Following postfixation the samples were washed in PBS for 1 h, and the cochlear duct containing the lagena and basilar papilla was removed. Next, the tissue was washed with Soerensen 0.1 M phosphate buffer (PB), dehydrated, and embedded in epoxy resin. After polymerization, the blocks were trimmed, and 500-nm sections at the level of the basilar papilla were prepared using a diamond knife on a Leica UCT ultramicrotome. Single sections were transferred onto the diamond chip in a drop of bidistilled water using a loop. They were air-dried under continuous visual inspection at a stereomicroscope to ensure flat mounting. All experiments were performed in accordance with an existing ethical framework (GZ:214635/2015/20) granted by the City of Vienna (Magistratsabteilung 58).

The substrates used in this experiment were 100 oriented chemical vapor deposition grown diamond from Delaware Diamond Knives. Nitrogen vacancy centers were created by implanting 15N with a dose of 11013 cm 2 at 4 keV and an implant angle of 7 before annealing at 1,000C. After annealing, the spatial density of NV centers in the diamond is approximately 11011 cm 2 (27). Of the NVs on the surface, 75 to 80% exist in the negatively charged state used for magnetic imaging (28). The external magnetic field used to magnetize the cuticulosomes was provided by neodymium magnets positioned using Scientifica motorized micromanipulators or a Physik Instruments motorized XYZ stage. A microwave signal is generated from an Agilent MXG N5183A analog signal generator with the signal then being amplified and delivered to the diamond sample by gold omega-shaped antennas printed on glass coverslips. Microwave switching is provided by a transistortransistor logicdriven Mini-Circuits microwave switch (ZASWA-2-50DR+). Laser excitation is provided by a Lighthouse Photonics Sprout-G with laser switching provided by acousto-optic modulators (AOMs) with the radio frequency (RF) to the AOM being produced by a MOGLabs Agile RF synthesizer. The fluorescence produced by the nitrogen vacancy layer was separated from the excitation using a dicroic mirror before being collected by an Andor Neo 5.5 sCMOS camera or an Andor Zyla 5.5 sCMOS camera. The pulses required for the control of the AOM, microwave switch, and camera shutter are produced using a SpinCore Pulse blaster ESR-Pro-500. Nikon oil immersion objectives with a numerical aperture of 1.30 were used for these experiments. The laser power at the back of the objective was 250 mW, which corresponds to a power density of 1.7 kW mm 2.

The magnetic forces due to several different mechanisms were calculated to determine the plausibility of cuticulosomes acting as mediators of geomagnetic field information. The torque resulting from misalignments between the geomagnetic field and the magnetic moment of cuticulosomes, the magnetic force acting between cuticulosomes in close proximity, and the magnetic force resulting from the interaction between the magnetic moment of cuticulosomes and the spatial gradient of the geomagnetic field were calculated. These calculations resulted in forces at least five orders of magnitude too small to gate known mechanoelectrical channels.

The torque acting on a cuticulosome is calculated following the method outlined by Winklhofer and Kirschvink (30). Torques can occur in magnetic particles with induced magnetizations. Magnetic anisotropy can produce a misalignment between the applied and induced fields. The torque is calculated as the cross product of the applied field and the net magnetization of the magnetic particle. Expanding the cross product allows for the determination of the three components of the torque as=12((bc)sin()sin(2)(ca)cos()sin(2)(ab)sin(2)sin2())B2V/0,[2]where and are the longitudinal and azimuthal angles, respectively, between the easy axis of the magnetic particle and the applied field; B is the applied field; and a,b, and c are the magnetic susceptibilities along the principal axes of the magnetic particle. Applying the above equations to a cuticulosome with a volume of 21019 m3, a=b=0.18, and c=0.19 in geomagnetic fields produces a torque of 2.61025 Nm and a corresponding force at the surface of the particle of 1.41018 N.

The force exerted by two cuticulosomes in close proximity to one another was also considered, following the equations derived by Davila et al. (31). This force increases as the distance between particles decreases, reaching a value of 1019 N when the distance between the particles is twice their radius.

Magnetic forces are also exerted on cuticulosomes when the applied magnetic field has a spatial gradient at the position of the cuticulosome. This is calculated as the gradient of the magnetic potential energy, U=12mBgeo, where m is the magnetization of the cuticulosome and Bgeo is the geomagnetic field (2). The magnetization can be calculated as the product of the magnetic susceptibility of the cuticulosome. Assuming a magnetic susceptibility, v, of 0.053, a geomagnetic field of 0.5 G, a cuticulosome radius of 365 nm, and a geomagnetic field gradient of 1106 G, a magnetic force of 11033 N (32) is estimated.

A pulsed-ODMR control sequence is applied to acquire ODMR spectra. The fluorescence is collected and binned with a coarseness of 2 2 by the camera. For each microwave frequency in the spectrum, an optical pulse was applied to spin-polarize the NVs into the 0 sublevel. A microwave pulse of a duration set to the time of the NV centers was applied, where the time is the duration which maximizes the efficiency of the spin transition when the microwave frequency is on resonance. A reference is also taken for each data point which consists of the same pulse sequence excluding the microwave pulse. The resulting data point for each microwave frequency is the ratio of the signal to the reference. The acquisition procedure is implemented using a custom LabVIEW program.

Quantum relaxometric microscopy maps the presence of magnetic noise by measuring the time taken for spin-polarized NVs to lose their polarization. The presence of magnetic noise with frequency spectra overlapping the spin transition frequencies of the NVs causes a more rapid loss of spin polarization or an increase in the T1 rate. The control sequence applied to acquire a data point of a T1 spectrum involves first optically polarizing the NV layer into the 0 state before allowing the spin state to evolve in the dark for some time, , before the final spin polarization is measured. A reference measurement for each time is also taken, in which a microwave pulse is applied prior to readout. The reference mitigates against unwanted effects including background light. Each data point in the resulting T1 spectrum is the ratio of the signal to the reference. The times are logarithmically spaced to maximize the collection of information about the NV decay rate, as collection of data points where is large is more time consuming than the collection of data points where is small. T1 spectra are collected across the full field of view of the sCMOS sensor, with the data binned with a coarseness of 2 2.

Custom MATLAB and Python programs were written to extract the resonances of interest from the collected data and extract magnetic information from the resonances. The analysis program bins the collected data with a coarseness of 2 2. The locations of resonant frequencies in ODMR spectra at each binned pixel are extracted by fitting a Lorentzian function,I()=1C22+(0)2,[3]where I() is the normalized fluorescence intensity as a function of the applied microwave frequency, C is the contrast of the ODMR peak, is a factor to specify the width of the Lorentzian fit, and 0 is the resonance frequency, to the experimental data at each binned pixel. To maximize the sensitivity the microwave driving power which maximizes the ratio of C to is sought and applied.

A Gaussian filter is applied to the image where the Gaussian kernel has a SD of 50 pixels to create a coarse background. The pixels overlapping the signal are replaced by pixels in the corresponding coarse background image to create an image with the signal removed, which enables the production of a background image which is less impacted by the presence of the signal. The background is then calculated by applying a Gaussian filter to the preprocessed image. The SD of the Gaussian kernel is set to 25 pixels. The signal was then obtained by subtracting the background from the unaltered image.

The metric for the stray magnetic field size employed here was produced by taking a line cut of a width of three pixels through the stray magnetic field signal maximum. A double Gaussian function was then fit to the line cut for each image, with the peak to peak magnitude of this fit providing a numerical indication of the stray magnetic field strength.

The same analysis programs are able to extract the T1 rates from T1 spectra. The analysis program again bins the data with a coarseness of 2 2. The stretched exponential function,I()=1+Cexp((T1)p)C,[4]where I() is the fluorescence intensity as a function of the dark time, C is the contrast, T1 is the T1 time, and p is the stretching exponent, is fit to the data at each binned pixel. The stretching exponent is included to account for effects such as the range of NV depths in the NV layer. A decrease in the value of T1 is expected to be observed in the vicinity of superparamagnetic material.

We thank Daniel McCloskey for many fruitful discussions throughout the project. The authors acknowledge support from the Australian Research Council through various fellowships to L.C.L.H. (FL130100119), L.T.H. (DE200101785), and J.-P.T. (DE170100129). R.W.d.G. is supported by an Australian Government Research Training Program Scholarship. D.A.K. is supported by the European Research Council (Grants 336725 and 819336) and the Austrian Science Fund (Grant Y726). E.P.M. is supported by the European Research Council (Grant 948728).

Author contributions: E.P.M., D.A.K., L.C.L.H., and D.A.S. designed research; R.W.d.G., J.M.M., L.T.H., and E.P.M. performed research; R.W.d.G., J.M.M., L.T.H., J.-P. T., L.C.L.H., and D.A.S. analyzed data; and R.W.d.G., E.P.M., D.A.K., L.C.L.H., and D.A.S. wrote the paper.

The authors declare no competing interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2112749118/-/DCSupplemental.

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Quantum magnetic imaging of iron organelles within the pigeon cochlea - pnas.org

Most modern devices around the world use GPS for wayfinding thanks to atomic clocks, which are known for extremely accurate timekeeping, hold the network of satellites perfectly in sync. But GPS signals can be jammed or spoofed, potentially disabling navigation systems on commercial and military vehicles.

Now, Sandia National Laboratories has designed and built the avocado-sized vacuum chamber as a core technology for next-generation navigation systems that dont rely on GPS satellites. Based on the idea that was used in missiles during the Second World War, the avocado-shaped system is the first device that is small, energy-efficient, and reliable enough to potentially move quantum sensors sensors that use quantum mechanics to outperform conventional technologies from the lab into commercial use.

Quantum sensors are a growing field, and there are lots of applications you can demonstrate in the lab, said Sandia postdoctoral scientist Bethany Little, who is contributing to the research. But when you move it into the real world, there are lots of problems you have to solve. Two are making the sensor compact and rugged. The physics takes place all in a cubic centimeter (0.06 cubic inches) of volume, so anything larger than that is wasted space.

Schwindt partnered with Sandia materials scientists to build the chamber out of titanium metal and sapphire. These materials are especially good at blocking out gasses like helium, which can squeeze through stainless steel and Pyrex glass. This self-contained system uses accelerometers and gyroscopes to calculate where the navigation device is in relation to a fixed, known position by measuring every rotation and movement of the device along all three axes. If these measurements are accurate enough, the results can rival those of GPS.

In new work, scientists have found that quantum sensing can work without a high-powered vacuum system. This shrinks the package to a practical size without sacrificing reliability.

Instead of a powered vacuum pump that whisks away molecules leaking in and wreck measurements, a pair of devices called getters to use chemical reactions to bind these intruders. Each is about the size of a pencil eraser, so you can fit them inside two narrow tubes sticking out of the titanium package. They also work without a power source.

Scientists continue to test the device to bring it to the required level of reliability. Their goal is to keep it sealed and operational for five years, an important milestone toward showing the technology is ready to be fielded. In the meantime, theyre exploring ways to streamline manufacturing.

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Sandias titanium avocado could allow for navigation without GPS satellites - Inceptive Mind

November 15, 2021• Physics 14, 157

A theoretical proposal offers a new way to relate the Higgs boson mass and the cosmological constant to each other and explain why these quantities appear to be implausibly tuned to values much smaller than expected.

What do the Higgs mass and Earths orbit ellipticity have in common? Both have values that are orders of magnitude smaller than theoretical estimates would suggest. These quantities appear to result from an extremely fine-tuned cancellation of two much larger quantitiesa fact that many physicists find implausible (Fig. 1). These and other fine tunings, however, might only be apparent, and their explanation may hold the key for paradigmatic changes in our understanding of nature. Particle physics features two of the most intriguing fine-tuning puzzles: the Higgs boson mass and the cosmological constant.

For a long time, the lore had it that these particle-physics tunings may be related to new symmetries, such as the elusive supersymmetry, or to statistical argumentsour fine-tuned Universe is just one of many possible multiverses. In recent years, however, new possible explanations have emerged [15], culminating in a new proposal by Nima Arkani-Hamed of the Institute for Advanced Study, New Jersey, Raffaele Tito DAgnolo of the University of Paris-Saclay, and Hyung Do Kim of Seoul National University [6]. The trio identified a new class of mechanisms for producing fine tunings, in which only specific values of the Higgs mass can trigger the formation of multiverses. The appeal of their model is that it makes testable predictionsthe existence of new, potentially observable Higgs particles.

To understand fine tuning, consider a measurable quantity that could be theoretically computed were it not for the fact that the necessary information is partially unavailable. Take, for example, the electric field near a charged conducting surface of which we can observe only a small region (Fig. 2). The field can be computed from the known charges in this region but may be affected by other, unknown charges. The observed value will be the sum of a known and unknown contribution. An observed value close to that derived from the known contribution would indicate that the unknown contribution isnt significant, and the difference may have a trivial explanation, such as some unaccounted-for difference in the conductors geometry.

But if the observed value is much smaller than that expected from the known contribution, it means that the known and unknown parts almost exactly cancel out. Often, this fine tuning reveals something new about the system. For instance, the conducting surface could extend to form a closed shell, or Faraday shield, inside which the electric field is zero. In this case, the tuning results from the symmetries of electromagnetism. It could also be that oppositely charged point particles are distributed so as to precisely cancel the electric field. This canceling could just be a statistical flukea chance arrangement that only occurs in one out of many possible experiments.

Similar examples abound in science. The mass of the electron appears to be fine tuned when one considers the large amount of energy that, according to classical electromagnetism, is stored in the electric field around the particle. But the explanation comes from a new particle, the positron, which influences the electrons mass through the effect of fleeting electron-positron pairs generated in the quantum-mechanical vacuum around the electron. The low eccentricity of Earths orbit is an example of an apparent fine tuning that can be explained statistically: Earth is just one among myriad exoplanets whose orbits eccentricities are suitable for life to develop. In both cases, the apparent fine tunings were resolved by disruptive scientific discoveriesthe discovery of the positron and of exoplanets.

Other fine tunings, however, still puzzle physicists, such as those found in the standard model of particle physics. The standard model has unparalleled predictive power, but two of its parametersthe Higgs mass and the cosmological constantappear to be extremely precisely tuned: To obtain the relatively small observed values of these two parameters, physicists require additional, unknown contributions that can almost exactly cancel other extremely large contributions from physics at scales that are accurately described by the standard model. If the standard model were to be valid up to the Planck scale, these additional contributions must be tuned to one part in 1034 for the Higgs and to one part in 10120 for the cosmological constant. Could these tunings also be signposts to conceptual breakthroughs? Concocting testable explanations has been a goal of theoretical physicists for the past four decades.

Traditional solutions fit in two categories: a so-called dynamical explanation and a multiverse explanation. The dynamical option implies new structure, particles, or symmetries, such as supersymmetrya theory in which the equations for matter and forces are identicalor Higgs compositenessa theory in which the Higgs boson is a bound state of new strong interactions. The multiverse solution, on the other hand, provides a statistical explanation of why the observed cosmological constant is so small: We just happen to inhabit the one anthropic Universe among 10120 possible universes whose cosmological constant enables life [7]. But observations have so far failed to deliver evidence for either the dynamical or the multiverse explanation, so researchers are starting to consider alternative scenarios.

The third route explored by Arkani-Hamed, DAgnolo, and Kim combines both dynamics and multiverses. Imagine a system whose energy spectrum depends on a parameter and exhibitsfor special values of this parametera multiplicity of nearly degenerate ground states (a situation similar to that encountered in condensed-matter experiments, where the potential energy can be easily tweaked via experimental knobs). The researchers consider a particle-physics system where the special parameter is the Higgs mass. They show that this scenario requires the notion of triggers: certain couplings of the Higgs to other particles or forces that would cause the Higgs mass to affect other physical observables. In this scenario, nearly degenerate statesin this case, multiversesonly emerge for specific Higgs mass values. These triggers address both fine tunings at once because the multiverse allows for the existence of an anthropic universe. Unlike the original multiverse solution, however, triggers are falsifiable, as they are associated with new couplings or new particles that can be searched for. And unlike dynamical solutions, triggers dont imply new forms of symmetry that have so far eluded detection.

The trios calculations show that there are only a handful of possibly relevant triggers (in the standard model but also, surprisingly, in theories that extend the standard model) and that the theory can deliver precise predictions for each trigger possibility. The most interesting trigger possibility involves the existence of further Higgs particles (a two-Higgs doublet model) with masses at or below the known Higgs boson mass (125 GeV). Such a scale is within reach of collider experiments, including those involving rare B-meson decays at the LHCb experiment or top decays at CERNs ATLAS and CMS experiments. There is still a large portion of parameter space that is amenable to exploration, and the new theory of triggers pinpoints promising search targets whose discovery would require much more than a tuning of our scientific theories.

Francesco Riva is an assistant professor of theoretical particle physics at the University of Geneva. He obtained his Ph.D. at the University of Oxford, UK, under the supervision of John March-Rusell. He then held postdoctoral positions at the Institute for High Energy Physics, Spain, the Swiss Federal Institute of Technology in Lausanne, and CERN, before joining the University of Geneva in 2018. His work focuses on theoretical and phenomenological aspects of particle physics beyond the standard model, with research interests ranging from studying the properties of the Higgs particle at the Large Hadron Collider to understanding gravity at microscopic scales. See https://www.francesco-riva.com

A new technique in which atoms move slowly through a diffraction grating lets researchers measure the tiny Casimir-Polder interaction, a force that arises from quantum vacuum fluctuations. Read More

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A Third Way to Explain Fine Tuning - Physics

Quantum computing has the potential to fundamentally transform the technology industry by applying the weird effects of the quantum realm to complex business problems. But right now, quantum computing faces a more mundane problem itself: finding enough recruits.

Demand for digital skills in the workplace has been on a steady upward trend for years, but the sudden increased reliance on technology since the start of 2020 has made competition in tech recruitment even more fierce.

The CIO's guide to Quantum computing

Quantum computers offer great promise for cryptography and optimization problems, and companies are racing to make them practical for business use. ZDNet explores what quantum computers will and wont be able to do, and the challenges that remain.

Read More

The challenge is even greater for organizations dealing in highly specialized technologies. Quantum computing, for example, combines a variety of specialist fields such as quantum theory, advanced mathematics, and computer science that aren't seen on your typical CV, shrinking the talent pool considerably for companies looking to hire in this nascent, but increasingly competitive, industry.

SEE:Quantum computing's next big challenge: A quantum skills shortage

"It is incredibly small," says Samantha Edmondson, head of talent at British quantum computing startup, Universal Quantum, which is on a mission to build the world's first million-qubit quantum computer.

"Say if we were looking to hire an experienced quantum physicist that had the kind of expertise we needed, then yes, you're looking at a small handful of academic groups across the world that you can really pick from."

Quantum computers operate on inherently different principles to classical computers, requiring a new approach to problem-solving and a workforce consisting of academic, technical, and businesses expertise.

No one candidate is going to possess all of these. "It involves so many different skills: we need classical hardware engineers, we need software engineers, we need mathematicians, we need simulation and modelling experts," says Edmondson.

"I think the challenge for us is, if we go to hire a classical engineer, they don't have the physics background; if we hire a physicist, they're not used to working with classical hardware engineering analogue design is new to them."

Another fundamental challenge for businesses is getting people interested in technical fields to begin with.

Not only are fewer young people taking IT and STEM-related subjects at school, but research also suggests that younger generations aren't all too confident about their chances of landing a career in tech either.

Robert Liscouski, CEO of Quantum Computing Inc (QCI), says this is reflective of endemic problems in how young people are educated, which doesn't necessarily include skills that are transferrable into the modern, professional workforce. "I think we're not doing a very good job at all of preparing young people for these technology jobs," he tells ZDNet.

"I think we still have this 19th Century education going on that's really focused on educating children so they can work in factories."

Better education, meanwhile, remains out of reach for most. "Where I live in Northern Virginia, we have a couple of academies that are geared for really advanced education in the secondary school and high schoolThe admission requirements in those programmes are so competitive that kids need to be at the absolute top of their game," says Liscouski.

"That's great you want that advanced thinking. But we need to figure out how we kind of bring that into the entire high school system and inculcate these kids into thinking about technology differently."

One solution for the shortage of specialist tech talent is for employers to bring on employees that are not necessarily already experts in the field, and then train them up on the job.

For a field like quantum computing, this still means being selective in the candidates you can hire higher-level education and expertise in mathematics, physics, engineering, and coding are always going to rank highly, for instance. Even so, internships and training programs can help to lower the barriers to entry.

Universal Quantum runs a three-month internship scheme that's open to graduates who hold a master's in physics or mathematics. Typically, interns take on a specific project that they are given total responsibility for, with Universal Quantum providing support through one-on-one mentoring and drop-in sessions with quantum physicists.

SEE:What is quantum computing? Everything you need to know about the strange world of quantum computers

The internship culminates in them presenting their work to a large section of the company. "Typically, we'll speak to them at the beginning and get a sense of what their interests are, and then we'll match that to a company need we have," says Edmondson.

"They'll often say, 'I don't know anything about quantum' or 'I've never worked in quantum,' and we have to reassure them and say 'that's completely fine, we're happy to teach you that when you come here.' That's quite exciting to them."

Liscouski too believes that deep quantum expertise isn't necessarily a requirement for enterprises to begin taking advantage of quantum computing, although he acknowledges that not all companies have the resources to offer comprehensive training programmes. "It's very hard for small companies and it's very hard for medium-sized companies because you don't have that luxury of taking 10% of your workforce out and putting them in training for a period of time," he says.

"Typically, you hire people because you need them now, not because you need them in six months."

One alternative is to target students at university, college, or even school: something that QCI previously offered with its quantum computing clubs, where participants learn to use the company's software, Qatalyst.

"We're moving into actually the academic instructional program, where professors are using our software as part of their curriculum, and we've got a whole curriculum development programme for that," says Liscouski.

"We're trying to push this down to the lowest common denominator in terms of who can access it. We're even trying to get into high schools to help that workforce development."

Qatalyst is a quantum application accelerator that enables end users to transform real-world problems into quantum-ready requests, and then it processes those requests on a combination of classical computers and cloud-based quantum processors, including Ion-Q, D-Wave, and Rigetti.

SEE:Quantum computing: Getting it ready for business

It enables businesses to make use of quantum applications without needing to have their own quantum computers or specialists.

"It's intended to try to put that technology in the hands of folks who are trying to solve business problems without having to be quantum programmers," says Liscouski.

"Our focus on our platform and the development that we've done to connect to any number of quantum platforms, is to disintermediate, or de-emphasise, the need for this high-end talent that's going to make a program run on a quantum computer."

In many ways, QCI proposes a technical solution to a shortage of specialist skills -- although Liscouski acknowledges that technology on its own is not the be-all to end-all. "We still have this shortcoming of all of this talent that's going to make this stuff work at scale," he adds.

"Quantum programmes are different than classical programmes. The way you look at a problem classically is different to the way you look at a problem from a quantum point of viewThinking about those problems requires a different level of thinking than classical computers."

Given the scant interest in technology careers shown by Generation Z, outreach is going to play a significant role in putting burgeoning, next-generation technologies like quantum computing on their radars undoubtedly the first step to addressing any skills gaps.

Edmondson says tech organizations need to become involved in attracting young people at a grassroots level within schools, as well as getting more creative in how they portray opportunities in the tech sector. "It's definitely a responsibility of businesses to try to nurture the talent pool coming forward and undertake outreach that will assist with that and that's just getting young people excited about things," she says.

SEE:Tech jobs have an image problem, and it's making the skills shortage worse

"We set up a lab in Spitalfields Market in London in a huge shipping container and were giving live demonstrations and experiments. People would come in and we'd talk to them about what we were doing and get them excited. That's relatively small-scale right now, but if somebody goes away and because of that becomes excited to learn something or do a new subject, that's a win."

Liscouski says that exposure to new technologies from an early age will also play an important role in equipping the next-generation workforce with key digital skills and have them working on real-world problems. "I think there has to be either post-high school training capability, or post-college training capability, or colleges have to extend and think more broadly about what they're preparing students to do," he adds.

"Because, at the end of the day, quantum computing like any computer that we know of unless there is end-user adoption, unless there is a focus on what problems can be solved, it becomes a science experiment and is just going to stay in the research world."

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Quantum computing skills are hard to find. Here's how companies are tackling the shortage - ZDNet

In a new FLEET theoretical study published recently in PhysicalReview Letters, the so called smoking gun in the search for the topological magnetic monopole also known as the Berry curvature has been found.

The discovery is a breakthrough in the search for topological effects in non-equilibrium systems.

The group, led by UNSW physicist and Associate Professor, Dimi Culcer, identified an unconventional Hall effect, driven by an in-plane magnetic field in semiconductor hole systems that can be traced exclusively to the Berry curvature.

Enhanced topological effects will permit low-energy topological electronics to be viable for large-scale, room-temperature operation, and therefore support the IEEE roadmap towards future electronics sustainability.

Isolating topological responses in regular conductors has been a historically difficult task, says research team leader A/Prof Dimi Culcer (UNSW). Even though these topological responses are believed to be ubiquitous in solids.

Quantized responses, such as the quantum Hall and quantum spin-Hall effects provide a clear fingerprint of topology, yet these have only been observed in one-dimensional (1D) systems and are intimately connected with the existence of edge states.

An experimental set-up for measuring conventional Hall effect with magnetic field perpendicular to the surface. Credit: FLEET

In `regular conductors, meaning 2D and 3D systems, plenty of theoretical literature exists predicting topological contributions to e.g. the anomalous Hall effect, but these have never been observed unambiguously in a transport measurement.

There are two main reasons for this: (i) spin-up and spin-down electrons usually make opposite contributions, and these nearly cancel out; (ii) whatever is left is overwhelmed by disorder.

The new FLEET paper remedies this long-standing shortcoming by identifying a two-dimensional system in which the Berry curvature, and only the Berry curvature, is responsible for the Hall signal linear in the applied in-plane magnetic field.

Remarkably, all disorder contributions vanish: we are not aware of any other multi-dimensional system in which this is true, says lead author, UNSW PhD student James Cullen. Its experimental measurement is accessible to any state-of-the-art laboratory worldwide, hence we expect strong interest from experimentalists.

The research team sought the tell-tale mathematical trace called Berry curvature, which can be understood if we think of the concept of parallel transport that appears routinely in geometry and general relativity.

Think of a vector as an arrow that we place somewhere on the surface of a solid object, explains Dimi. Now we move the arrow around, making sure it always points at the same angle to the surface this is in fact like a human being walking along the surface of the Earth. We eventually bring the arrow back to the starting point after it has circled around, and we find that, in general, it points in a different direction it has magically rotated through some angle. The size of this angle is determined by the curvature of the surface.

Hall conductivity response to magnetic field. Credit: FLEET

In quantum mechanics, instead of vectors we have wave functions, but we can describe the dynamics using the same picture, and the curvature is called the Berry curvature.

The angle of rotation is replaced by the famous Berry phase, named after the mathematical physicist Prof Sir Michael Berry, who formulated the problem in the 1980s. Later on, building on work by Nobel laureate David Thouless, Qian Niu of UT Austin showed that the Berry curvature behaves like the coveted magnetic monopolebut not in real space, rather in momentum space, which is the space most condensed-matter physicists think in.

The Berry curvature drives topological effects in out-of-equilibrium systems because when an electric field is applied an electron is accelerated, so its momentum changes. When this happens its wave function changes slowly, in the same way that the `arrow is rotated in parallel transport, and as a result of this gradual rotation a transverse (Hall) current is generated. The Onsager relations, which are fundamental to non-equilibrium physics, say that the Hall current does not dissipate energy. The extreme case is the quantum anomalous Hall effect (QAHE), a quantum effect key to the function of topological materials, in which edge currents can flow with effectively zero electrical resistance.

(Quantum describes step transition in the transverse (Hall) resistance ie, it varies in discrete steps rather than smoothlywhile anomalous refers to the phenomenons occurrence in the absence of any applied magnetic field.)

Researchers seek to enhance QAHE in order to protect topological behaviour at higher temperatures, allowing for topological electronics that would be viable for room-temperature operation.

The significant reduction in electrical resistance permitted by room temperature QAHE would allow us to significantly reduce the power consumption in electronic devices, says Dimi.

Reference: Generating a topological anomalous Hall effect in a non-magnetic conductor: an in-plane magnetic field as a direct probe of the Berry curvature by James H. Cullen, Pankaj Bhalla, E. Marcellina, A.R. Hamilton and Dimitrie Culcer, 21 June 2021, Physical Review Letters.DOI 10.1103/PhysRevLett.126.256601

As well as support from theAustralian Research Council(Centres of Excellence program) the authors acknowledge the support of the National Key Research and Development Program (China), and the China Postdoctoral Science Foundation.

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Breakthrough Smoking Gun Discovery in Power Consumption in Electronic Devices - SciTechDaily

Illustration of a quantum wave packet in close vicinity of a conical intersection between two potential energy surfaces. The wave packet represents the collective motion of multiple atoms in the photoactive yellow protein. A part of the wave packet moves through the intersection from one potential energy surface to the other, while another part remains on the top surface, leading to a superposition of quantum states. Credit: DESY, Niels Breckwoldt

A new analytical technique is able to provide hitherto unattainable insights into the extremely rapid dynamics of biomolecules. The team of developers, led by Abbas Ourmazd from the University of WisconsinMilwaukee and Robin Santra from DESY, is presenting its clever combination of quantum physics and molecular biology in the scientific journal Nature. The scientists used the technique to track the way in which the photoactive yellow protein (PYP) undergoes changes in its structure in less than a trillionth of a second after being excited by light.

In order to precisely understand biochemical processes in nature, such as photosynthesis in certain bacteria, it is important to know the detailed sequence of events, Santra explains their underlying motivation. When light strikes photoactive proteins, their spatial structure is altered, and this structural change determines what role a protein takes on in nature. Until now, however, it has been almost impossible to track the exact sequence in which structural changes occur. Only the initial and final states of a molecule before and after a reaction can be determined and interpreted in theoretical terms. But we dont know exactly how the energy and shape changes in between the two, says Santra. Its like seeing that someone has folded their hands, but you cant see them interlacing their fingers to do so.

Whereas a hand is large enough and the movement is slow enough for us to follow it with our eyes, things are not that easy when looking at molecules. The energy state of a molecule can be determined with great precision using spectroscopy; and bright X-rays for example from an X-ray laser can be used to analyze the shape of a molecule. The extremely short wavelength of X-rays means that they can resolve very small spatial structures, such as the positions of the atoms within a molecule. However, the result is not an image like a photograph, but instead a characteristic interference pattern, which can be used to deduce the spatial structure that created it.

Since the movements are extremely rapid at the molecular level, the scientists have to use extremely short X-ray pulses to prevent the image from being blurred. It was only with the advent of X-ray lasers that it became possible to produce sufficiently bright and short X-ray pulses to capture these dynamics. However, since molecular dynamics takes place in the realm of quantum physics where the laws of physics deviate from our everyday experience, the measurements can only be interpreted with the help of a quantum-physical analysis.

A peculiar feature of photoactive proteins needs to be taken into consideration: the incident light excites their electron shell to enter a higher quantum state, and this causes an initial change in the shape of the molecule. This change in shape can in turn result in the excited and ground quantum states overlapping each other. In the resulting quantum jump, the excited state reverts to the ground state, whereby the shape of the molecule initially remains unchanged. The conical intersection between the quantum states therefore opens a pathway to a new spatial structure of the protein in the quantum mechanical ground state.

The team led by Santra and Ourmazd has now succeeded for the first time in unraveling the structural dynamics of a photoactive protein at such a conical intersection. They did so by drawing on machine learning because a full description of the dynamics would in fact require every possible movement of all the particles involved to be considered. This quickly leads to unmanageable equations that cannot be solved.

The photoactive yellow protein we studied consists of some 2000 atoms, explains Santra, who is a Lead Scientist at DESY and a professor of physics at Universitt Hamburg. Since every atom is basically free to move in all three spatial dimensions, there are a total of 6000 options for movement. That leads to a quantum mechanical equation with 6000 dimensions which even the most powerful computers today are unable to solve.

However, computer analyses based on machine learning were able to identify patterns in the collective movement of the atoms in the complex molecule. Its like when a hand moves: there, too, we dont look at each atom individually, but at their collective movement, explains Santra. Unlike a hand, where the possibilities for collective movement are obvious, these options are not as easy to identify in the atoms of a molecule. However, using this technique, the computer was able to reduce the approximately 6000 dimensions to four. By demonstrating this new method, Santras team was also able to characterize a conical intersection of quantum states in a complex molecule made up of thousands of atoms for the first time.

The detailed calculation shows how this conical intersection forms in four-dimensional space and how the photoactive yellow protein drops through it back to its initial state after being excited by light. The scientists can now describe this process in steps of a few dozen femtoseconds (quadrillionths of a second) and thus advance the understanding of photoactive processes. As a result, quantum physics is providing new insights into a biological system, and biology is providing new ideas for quantum mechanical methodology, says Santra, who is also a member of the Hamburg Cluster of Excellence CUI: Advanced Imaging of Matter. The two fields are cross-fertilizing each other in the process.

Reference: Few-fs resolution of a photoactive protein traversing a conical intersection by A. Hosseinizadeh, N. Breckwoldt, R. Fung, R. Sepehr, M. Schmidt, P. Schwander, R. Santra and A. Ourmazd, 3 November 2021, Nature.DOI: 10.1038/s41586-021-04050-9

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Clever Combination of Quantum Physics and Molecular Biology - SciTechDaily

We like to think that things are there even when we aren't looking at them. But that belief might soon be overturned thanks to a new test designed to tell us if quantum weirdness persists in macroscopic objects

By Thomas Lewton

Olena Sergienko/Unsplash

THERE is an old philosophy question about a tree in a forest. If it falls with nobody there to hear it, does it make a sound? Ask a quantum physicist and they might say the sound was there but you couldnt be sure the tree was.

Quantum mechanics has long pushed the boundaries of our understanding of reality at its tiniest. Countless experiments have shown that particles spread out like waves, for instance, or seem be in more than one place at once. In the quantum world, we can only know the likelihood that something will appear in one place or another until we look, at which point it assumes a definite position. This troubled Albert Einstein. I like to think that the moon is there even if I am not looking at it, he said.

Now, a new class of experiments is putting Einsteins conviction to the test, seeing if quantum weirdness stretches beyond the tiny world of quarks, atoms and qubits into the everyday world of tables, chairs and, well, moons. If you can go from one atom to two atoms to three to four to five to a thousand, is there any reason why it stops? says Jonathan Halliwell at Imperial College London.

These experiments are not just investigating whether there is a hard boundary between the quantum and classical worlds, but also probing the true nature of reality. If the work goes as some theorists expect, it might just kick the legs out from under one of our most firmly held beliefs: that things exist regardless of whether we are looking at them.

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The quantum experiment that could prove reality doesnt exist - New Scientist