Daily Archives: September 1, 2021

The American physicist Richard Feynman thought that nobody understands quantum mechanics. That is no longer true. Smartphones, nuclear plants, medical scans and laser-operated doors have been built with insights from the physics that governs the subatomic level. What perplexes many is that the quantum world is governed by rules that run counter to classical notions of physical laws.

In quantum mechanics, nature is not deterministic. Subatomic particles do not travel a path that can be plotted. It is possible only to calculate the probability of finding these specks at a particular point. Where such calculations leave physics, that hardest of the hard sciences, has troubled its greatest minds. Albert Einstein thought the idea that an element of chance lay deep in science was absurd. God does not play dice, he famously declared.

Physics is full of predictions that could be confirmed or denied once the technology to examine them had caught up. Einstein was proved wrong. In his new book, Helgoland, the Italian theoretical physicist Carlo Rovelli narrates how a scientific revolution was started by a young German physicist, Werner Heisenberg. He first devised quantum theory during a summer holiday in 1925 spent on the barren North Sea island of the books name.

The world, thought Heisenberg, could not be stated exactly, merely known through models of uncertainty and probability. He won a Nobel prize in 1932, though his achievements were tarnished by tacit support of Nazi Germany. The theory was that the world people experience is decided upon when many possibilities of the quantum world collapse to become the certainty of the classical one. This led to Erwin Schrdingers cat-in-a-box thought experiment. Quantum theory suggested that only by opening the container could it be determined if the feline was dead or alive. If the box remains closed the unfortunate cat is in limbo in a state between life and death, a superposition of possibilities.

Prof Rovelli dismantles attempts to explain away the indeterminacy of quantum mechanics. First, he takes on the many worlds thesis, which claims that every possible alternative exists and we just see one of them. In short, Schrdingers cat is alive in one universe and dead in another. Some claim that Heisenbergs work would collapse for some as yet undiscovered macroscopic entity. In this explanation, the cat is too big to be subject to quantum physics. More recently, it has been argued that quantum systems do have definite properties; we just do not know enough about those systems to precisely predict their behaviour. But in Helgoland, this is dismissed as an attempt to return to a pre-1920s view.

Quantum theory, Prof Rovelli says, views the physical world as a net of relations. Objects are its nodes. In his relational interpretation, Schrdingers cat has properties only when it interacts with something else. When it is not interacting, it has no properties. Prof Rovelli reaches for Buddhist thought to explain his ideas. He claims that if nothing exists in itself, surely everything exists solely through dependence. Facts are relative, he writes, opening up a debate that is likely to last longer than the century of argument that it seeks to close.

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The Guardian view on the quantum world: where facts are relative - The Guardian

Someone once said: "The world is all that is the case."

But, is it?

Researchers performing a long-awaited experiment created different realities that are irreconcilable, proving that objective facts can be made to exhibit properties that cannot cohere, according to a recent study shared on a preprint server.

Sound confusing? You're not alone in thinking so, as this all involves some pretty complicated physics. But in short, the takeaway is this: Reality is at odds with itself.

Nobel Prize-winner Eugene Wigner described a thought experiment in 1961 that highlighted an uncommon paradox of quantum mechanics. Specifically, it reveals the strangeness of the universe when two observers, like Wigner and his friend, observe two distinct realities. Since the thought experiment, physicists have used it to explore the very nature of measurement, in addition to the bizarre idea of whether objective facts actually exist or not. This is a pretty crucial feature of science, since empirical inquiry works to establish objective facts.

But if there aren't any facts, how can science presume to describe a real world in the first place?

For decades (and philosophically, much longer), this has served as a great bit for entertaining dinner guests, but Wigner's thought experiment wasn't really anything more than that. Until now.

In 2020, physicists realized that recent quantum technology advances had made it possible to create Wigner's Friend test in a real-world experiment. In essence, we can create different realities, and compare them in a lab to see if they can be reconciled, or cohere, in one system. And researcher Massimiliano Proietti of Heriot-Watt University, Edinburgh, along with a handful of researchers, said they performed this long-awaited experiment for the first time: Creating distinct realities, compare-and-contrasting them, and discovering that they are, in fact, irreconcilable.

Wigner's initial thought experiment was simplistic in principle, starting with a single polarized photon that can have either vertical or horizontal polarization, upon measuring. The laws of quantum mechanics hold that a photon exists in both states of polarization simultaneously, in what's called superposition. In his thought experiment, Wigner imagined a friend measuring the state of a photon in a different lab and recording the result while Wigner watched from afar. He has no clue what his friend's measurement is, and is thus forced to assume that the photon and its measurement are in a state of superposition of every possible outcome for the experiment.

Wigner can say, however, that the "fact" of the superposition's existence is real. And, strangely, this state of affairs suggests that the measurement can't have taken place. Obviously, this stands in direct contradiction to Wigner's friend's point-of-view, who just measured and recorded the photon's polarization. He can even call Wigner and tell him the measurement was taken, without revealing the results. This means there are two realities at odds with one another, and it "calls into question the objective status of the facts established by the two observers," explained Proietti and colleagues, in an MIT Technology Review report.

And the new research reproduced Wigner's thought experiment by using entanglement techniques for many particles at the same time.

This is a breakthrough experiment from Prioretti and his colleagues. "In a state-of-the-art 6-photon experiment, we realize this extended Wigner's friend scenario," they added in the report. And it raised some baffling questions that have forced physicists to confront the nature of reality. There might be a loophole to some assumptions that made this unknowable reality conclusion necessary, but if everything holds up to future scrutiny, it turns out reality does not exist.

So the next time your friends think something is or isn't the case, consider interjecting with an argument from quantum physics: they're both wrong, and so are you, because even the simple fact of the disagreement itself isjust another illusion.

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New Physics Experiment Indicates There's No Objective Reality - Interesting Engineering

Using a quirk of quantum mechanics, researchers have created a beryllium crystal capable of detecting incredibly weak electromagnetic fields. The work could one day be used to detect hypothetical dark matter particles called axions.

The researchers created their quantum crystal by trapping 150 charged beryllium particles or ions using a system of electrodes and magnetic fields that helped overcome their natural repulsion for each other, Ana Maria Rey, an atomic physicist at JILA, a joint institute between the National Institute of Standards and Technology and the University of Colorado Boulder, told Live Science.

Related: The 18 biggest unsolved mysteries in physics

When Rey and her colleagues trapped the ions with their system of fields and electrodes, the atoms self-assembled into a flat sheet twice as thick as a human hair. This organized collective resembled a crystal that would vibrate when disturbed by some outside force.

"When you excite the atoms, they don't move individually," Rey said. "They move as a whole."

When that beryllium "crystal" encountered an electromagnetic field, it moved in response, and that movement could be translated into a measurement of the field strength.

But measurements of any quantum mechanical system are subject to limits set by the Heisenberg uncertainty principle, which states that certain properties of a particle, such as its position and momentum, can't simultaneously be known with high precision.

The team figured out a way to get around this limit with entanglement, where quantum particles' attributes are inherently linked together.

"By using entanglement, we can sense things that aren't possible otherwise," Rey said.

In this case, she and her colleagues entangled the motions of the beryllium ions with their spins. Quantum systems resemble tiny tops and spin describes the direction, say up or down, that those tops are pointing.

When the crystal vibrated, it would move a certain amount. But because of the uncertainty principle, any measurement of that displacement, or the amount the ions moved, would be subject to precision limits and contain a lot of what's known as quantum noise, Rey said.

To measure the displacement, "we need a displacement larger than the quantum noise," she said.

Entanglement between the ions' motions and their spins spreads this noise out, reducing it and allowing the researchers to measure ultra-tiny fluctuations in the crystal. They tested the system by sending a weak electromagnetic wave through it and seeing it vibrate. The work is described Aug. 6 in the journal Science.

The crystal is already 10 times more sensitive at detecting teensy electromagnetic signals than previous quantum sensors. But the team thinks that with more beryllium ions, they could create an even more sensitive detector capable of searching for axions.

Axions are a proposed ultralight dark matter particle with a millionth or a billionth the mass of an electron. Some models of the axion suggest that it may be able to sometimes convert into a photon, in which case it would no longer be dark and would produce a weak electromagnetic field. Were any axions to fly through a lab containing this beryllium crystal, the crystal might pick up their presence.

"I think it's a beautiful result and an impressive experiment," Daniel Carney, a theoretical physicist at Lawrence Berkeley National Laboratory in Berkeley, California, who was not involved in the research, told Live Science.

Along with helping in the hunt for dark matter, Carney believes the work could find many applications, such as looking for stray electromagnetic fields from wires in a lab or searching for defects in a material.

Originally published on Live Science.

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Quantum crystal could reveal the identity of dark matter - Space.com

New research reveals hints of quantum states in tiny proteins called microtubules inside brain cells. If the results stand up, the idea that consciousness is quantum might come in from the cold

By Thomas Lewton

Skizzomat

IF IT is a controversial idea that warm, wet life might exploit quantum magic, thats nothing compared with certain researchers convictions that quantum phenomena might help explain human consciousness.

Orchestrated objective reduction theory (Orch OR), originally proposed by physicist Roger Penrose and anaesthesiologist Stuart Hameroff in the 1990s, seeks to bridge the gulf between physical matter and felt experience. The idea is that consciousness arises when gravitational instabilities in the fundamental structure of space-time collapse quantum wave functions in tiny proteins called microtubules, which are found inside neurons.

It is heady stuff, but if pulling together quantum mechanics, gravity and consciousness in one fell swoop sounds too good to be true, it might be. Orch ORs critics argue that any quantum coherence inside microtubules would fall apart in the warm and noisy environs of grey matter long before it could have any effect on the workings of neurons.

Yet in one tantalising experiment last year, as-yet unpublished, Jack Tuszynski at the University of Alberta in Canada and Aristide Dogariu at the University of Central Florida found that light shone on microtubules was very slowly re-emitted over several minutes a hallmark of quantum goings-on. This is crazy, says Tuszynski, who set about building a theoretical microtubule model to describe what he was seeing.

Gregory Scholes, a biochemist at Princeton University, is studying microtubules for signs of similar quantum effects. Initial experiments point to long-lived, long-range collective behaviour among molecules in the structures. Both groups plan to test whether anaesthetics, which switch consciousness on and off, have any impact on microtubules. There is amazing structure and synchrony in biological systems, says

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Can quantum effects in the brain explain consciousness? - New Scientist

Complementarity relation of wave-particle duality is analyzed quantitatively with entangled photons as path detectors.

The twenty-first century has undoubtedly been the era of quantum science. Quantum mechanics was born in the early twentieth century and has been used to develop unprecedented technologies which include quantum information, quantum communication, quantum metrology, quantum imaging, and quantum sensing. However, in quantum science, there are still unresolved and even inapprehensible issues like wave-particle duality and complementarity, superposition of wave functions, wave function collapse after quantum measurement, wave function entanglement of the composite wave function, etc.

To test the fundamental principle of wave-particle duality and complementarity quantitatively, a quantum composite system that can be controlled by experimental parameters is needed. So far, there have been several theoretical proposals after Neils Bohr introduced the concept of complementarity in 1928, but only a few ideas have been tested experimentally, with them detecting interference patterns with low visibility. Thus, the concept of complementarity and wave-particle duality still remains elusive and has not been fully confirmed experimentally yet.

Figure 1. Double-path single-photon interferometer with controllable source purity used in our ENBS model. Two SPDC crystals, PPLN1 and PPLN2, are pumped and seeded simultaneously by the same pump and seed coherent lasers, respectively, resulting in the emission of two signal photons s1 or s2 for quantum interference detection at PD. Then, conjugate idler photons i1 and i2 provide the which-path (or which-source) information, where the controllable source purity is determined by the overlap between the SPACS of one of the idler modes and the unchanged coherent state of another idler mode. Two idler fields can be detected independently by detectors DA and DB. Credit: Institute for Basic Science

To address this issue, a research team from the Institute for Basic Science (IBS, South Korea) constructed a double-path interferometer consisting of two parametric downconversion crystals seeded by coherent idler fields, which is shown in Figure1. The device generates coherent signal photons (quantons) that are used for quantum interference measurement. The quantons then travel down two separate paths before reaching the detector. The conjugate idler fields are used for extracting path information with controllable fidelity, which is useful for quantitatively elucidating the complementarity.

In a real experiment, the source of quantons is not pure due to its entanglement with the remaining degrees of freedom. However, the quanton source purity is tightly bounded by the entanglement between the generated quantons and all the other remaining degrees of freedom by the relation s = (1 E2), which the researchers confirmed experimentally.

Figure 2. Quantitative complementarity relation of wave-particle duality. (A) Quantitative complementarity relation P2 + V2 = s2 with respect with respect to = 2 / 1 and = 2. Here, path predictability P represents particle-like behavior, while fringe visibility V represents wave-like behavior of the quanton in the double-path interferometer. The totality of complementarity is bounded by the source purity. (B) Source purity s of the quanton (signal photon) and entanglement E between the quanton and which-path (which-source) detector form another complementarity relation s2 + E2 = 1. These two measures are plotted with respect to = 2 / 1 and = 2.Credit: Institute for Basic Science

The wave-particle duality and the quantitative complementarity P2 + V2 = s2 (P, a priori predictability; V, visibility) were analyzed and tested using this entangled nonlinear bi-photon source (ENBS) system, where the superposition states of the quantons are quantum mechanically entangled with conjugate idler states in a controllable manner. It was shown that a priori predictability, visibility, entanglement (thus, source purity, and fidelity in our ENBS model) strictly depend on the seed beam photon numbers. This points to the potential application of this approach for the preparation of distant entangled photon states.

Figure 3. Fringe visibility V and a priori visibility V0 as functions of = 2 / 1 and = 2. Blue points are experimental data taken from the teams recent paper. Experimental data coincide with the visibility V, not a priori visibility V0 across the whole ranges of and ||. This plot validates the teams analysis of the ENBS experimental results in terms of the wave-particle duality and quantitative complementarity relations. Credit: Institute for Basic Science

Richard Feynman once stated that solving the puzzle of quantum mechanics lies in the understanding of the double-slit experiment. It is anticipated that the interpretation based on the double-path interferometry experiments with ENBS will have fundamental implications for better understanding the principle of complementarity and the wave-particle duality relation quantitatively.

Reference: Quantitative complementarity of wave-particle duality by Tai Hyun Yoon and Minhaeng Cho, 18 August 2021, Science Advances.DOI: 10.1126/sciadv.abi9268

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Experimental Confirmation of the Fundamental Principle of Wave-Particle Duality - SciTechDaily

Quantum computing is emerging as the next big thing in the world of technology owing to the advantages it offers over traditional computers, especially when it comes to rapid processing of complex calculations. Quantum computers are opening up new areas of research and are predicting outcomes at a faster pace than traditional computers. This is because unlike traditional computing, where basic information is stored in binaries, that is, in ones or zeros, quantum computing holds data in the form of quantum bits or qubits, that is, in combinations of all possible states, which are also referred to as superposition.

Quantum computing can be leveraged in areas such as artificial intelligence (AI) and machine learning, allowing for increased efficiency and better outcomes. Owing to the ability to generate optimized results, quantum computing is being used across various sectors. NASA is utilizing quantum computing to find safer ways of space travel, controlling air traffic, and so on, as mentioned in a GigaOm article. In 2019, automotive manufacturer Volkswagen used quantum computers to optimize traffic flow in Lisbon, as mentioned in a press release by the company.

Since quantum computing utilizes quantum physics, that is, studying particles at the subatomic level, drug research and discovery can take a leap forward as researchers can study the properties of molecules in detail. Apart from that, the financial sector stands to benefit from quantum computing. Per a report by the IBM Institute for Business Value, quantum computing can be utilized in areas such as risk profiling, predicting and targeting as well as optimization of trading.

Reflective of the positives that quantum computing stands to offer to myriad industries, the quantum computing market is expected to continue to grow. Gartner stated that by 2025, about 40% of large companies are set to undertake initiatives related to quantum computing, as mentioned in a Wall Street Journal article. In fact, per a report by Markets and Markets, the quantum computing market is estimated to witness a CAGR of 30.2% from 2021 to 2026.

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Since quantum computing hardware is expensive and hard to maintain, firms are expected to use the technology via cloud platforms. In 2019, a report by Gartner had stated that by 2023, 95% of organizations will use Quantum Computing as a Service for conducting research on quantum computing strategies.

Quantum computing is emerging as the next step of technological advancement and is set to witness growth going forward. This seems like a prudent time to keep a close watch on companies that can utilize the potential of quantum computing in the coming days. We have selected four such stocks that carry a Zacks Rank #2 (Buy) or 3 (Hold). You can see the complete list of todays Zacks #1 Rank (Strong Buy) stocks here.

Microsoft Corporation MSFT takes a comprehensive approach to delivering quantum and the approach innovates in parallel at all layers of the computing stack, including controls, software and development tools and services. The company also offers Azure Quantum, which assembles and curates several quantum resources for developers and customers across all industries.

Shares of Microsoft have risen 34.8% year to date and it currently has a Zacks Rank #2. The Zacks Consensus Estimate for its current-year earnings has moved up 3.6% over the past 60 days. The companys expected earnings growth rate for the current year is 8%.

NVIDIA Corporation NVDA offers cuQuantum, which is a software development kit of optimized libraries and tools for accelerating quantum computing workflows.

Shares of this Zacks Rank #2 company have gained 73.4% year to date. The Zacks Consensus Estimate for its current-year earnings has risen 6.1% over the past 60 days. The companys expected earnings growth rate for the current year is 68%.

Alphabet Inc.s GOOGL Google offers Quantum AI, which is advancing the state-of-the-art quantum computing and developing tools for researchers for operating beyond classical capabilities. On May 18, Google unveiled its new Quantum AI campus in Santa Barbara, CA, and the campus includes Googles first quantum data center, quantum hardware research laboratories, and quantum processor chip fabrication facilities.

Shares of Alphabet have risen 64.3% year to date and the stock currently carries a Zacks Rank #3. The Zacks Consensus Estimate for its current-year earnings has moved 14.3% north over the past 60 days. The companys expected earnings growth rate for the current year is 73.8%.

Intel Corporation INTC designs, manufactures, and sells essential technologies for the cloud, smart, and connected devices. Intel has been collaborating with QuTech and providing engineering resources for accelerating developments. On May 12, Intel, in collaboration with QuTech, reported that using its cryogenic controller Horse Ridge, it was able to control qubits even in low, cryogenic temperatures, which can lead to solving the problem of quantum scaling or wiring bottleneck.

Shares of Intel have risen 8.2% year to date. The Zacks Consensus Estimate for its current-year earnings has risen 3.7% over the past 60 days. This Zacks Rank #3 companys expected earnings growth rate for the next five years is 7.5%.

Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free reportIntel Corporation (INTC) : Free Stock Analysis ReportMicrosoft Corporation (MSFT) : Free Stock Analysis ReportNVIDIA Corporation (NVDA) : Free Stock Analysis ReportAlphabet Inc. (GOOGL) : Free Stock Analysis ReportTo read this article on Zacks.com click here.Zacks Investment Research

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4 Stocks to Benefit From the Potential of Quantum Computing - Yahoo Finance

Suppose you and your cousin are about to inherit some moneyand you each have a version of the will on your computer. What is the least amount of information your computers must share to determine whether the versions are the same?

This hypothetical scenario raises a communication complexity problem. These problems deal with how much information you need to exchange from computer to computer, orfrom network node to node to perform a certain task or function. The less information transmitted to complete the task, the more energy and time saved and the more privacy is preserved.

Li QianandHoi-Kwong Lo, both professors in the University of Toronto's Edward S. Rogers Sr. department of electrical and computer engineeringin the Faculty of Applied Science & Engineering,and Xiaoqing Zhong, a PhD candidate in the department of physics in the Faculty of Arts & Science,have developed an improved quantum fingerprinting (QF) protocol to more efficiently and securely solve these types of problems, which come up in contexts such as computer networking andVery Large Scale Integration (VLSI) chip design, among other situations.

The teams protocol used the many different frequencies of a photons quantum state a novel approach to encode information. Their paper wasrecently published inNature Communications.

Lets say you and your cousin each have a data file of a million bytes a megabyte, Qian says. In classical protocol, the smallest fingerprint required to determine whether the information is the same to a certainty near 100 per centis found by the square root of the total number of bits. So, a one megabyte file would require the transmission of roughly 300 bytes. With quantum fingerprinting, the amount scales logarithmically: a one megabyte file would only require around three bytes.

The advantage becomes even more pronounced as the files get bigger, Qian adds.

As the data string becomes larger and larger, quantum fingerprinting can drastically reduce the amount of information that you need to exchange.

The QF protocol is achieved by exploiting a property called superposition. In classical communication, a photon encodes information as either a one or zero, but in quantum mechanics a photon can exist in many states between this binary. The possible combinations of these intermediate states are what alloweach single photon to carry far more information, reducing the overall number and saving time, energy and bandwidth.

In addition, it greatly diminishes information leaks, Qian says, which lessens privacy and security concerns.

One challenge of implementing the QF is that the detectors used to register the photons are very sensitive and can produce signal noise. Currently, superconducting photon detectors must be housed in cryogenic dewars, which cool down the environment to milli-Kelvin temperatures. Still, random errors creep in.

The teams improved QF protocol used a technique called multiplexingthe simultaneous sending and measuring of many frequencies of photons to speed up communication time and make QF much less susceptible to detector noise. In the lab, they demonstrated this measurement with six frequencies, but in principle it could be thousands, says Qian.

It makes QF a more practical option, she says. We can use off-the-shelf components: run-of-the-mill semiconductor-based single photon detectors, which are orders of magnitude cheaper than superconductor detectors.

Though QF is accessible technology in todays marketplace, quantum communication is hampered by a lack of compatible infrastructure. Quantum signals are fragileand, though they can coexist with the classical signal in our present fibre optic network, they are easily contaminated. Much of the data terminal equipment in the existing network, such as amplifiers, switches and routers, is not suitable for quantum signals.

More research in progress at the joint labs of Qian and Lo needs to be done to bring quantum and classical signals together in the same optical fibre.

Engineering often finds a balance between the practical and the theoretical, says ProfessorDeepa Kundur, chair of the department of electrical and computer engineering.And Professors Qian and Los research is a great example of this. Theyve fine-tuned a cutting-edge protocol with sights firmly set on the future landscape of telecommunications and by doing soare helping to realize it.

When asked what motivated her to work on quantum technologies, Qian points to the uniqueness of quantum properties.

Theyre simply not found anywhere else in nature, she says. Think of how the unique property of laserscoherent light revolutionized optical technologies in a few short decades. I am convinced the quantum properties of photons will do the same.

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U of T researchers develop new quantum 'fingerprinting' protocol to improve information exchange - News@UofT