Daily Archives: September 17, 2022

Whoever said, You cant get something from nothing must never have learned quantum physics. As long as you have empty space the ultimate in physical nothingness simply manipulating it in the right way will inevitably cause something to emerge. Collide two particles in the abyss of empty space, and sometimes additional particle-antiparticle pairs emerge. Take a meson and try to rip the quark away from the antiquark, and a new set of particle-antiparticle pairs will get pulled out of the empty space between them. And in theory, a strong enough electromagnetic field can rip particles and antiparticles out of the vacuum itself, even without any initial particles or antiparticles at all.

Previously, it was thought that the highest particle energies of all would be needed to produce these effects: the kind only obtainable at high-energy particle physics experiments or in extreme astrophysical environments. But in early 2022, strong enough electric fields were created in a simple laboratory setup leveraging the unique properties of graphene, enabling the spontaneous creation of particle-antiparticle pairs from nothing at all. The prediction that this should be possible is 70 years old: dating back to one of the founders of quantum field theory, Julian Schwinger. The Schwinger effect is now verified, and teaches us how the Universe truly makes something from nothing.

This chart of the particles and interactions details how the particles of the Standard Model interact according to the three fundamental forces that Quantum Field Theory describes. When gravity is added into the mix, we obtain the observable Universe that we see, with the laws, parameters, and constants that we know of governing it. Mysteries, such as dark matter and dark energy, still remain.

In the Universe we inhabit, its truly impossible to create nothing in any sort of satisfactory way. Everything that exists, down at a fundamental level, can be decomposed into individual entities quanta that cannot be broken down further. These elementary particles include quarks, electrons, the electrons heavier cousins (muons and taus), neutrinos, as well as all of their antimatter counterparts, plus photons, gluons, and the heavy bosons: the W+, W-, Z0, and the Higgs. If you take all of them away, however, the empty space that remains isnt quite empty in many physical senses.

For one, even in the absence of particles, quantum fields remain. Just as we cannot take the laws of physics away from the Universe, we cannot take the quantum fields that permeate the Universe away from it.

For another, no matter how far away we move any sources of matter, there are two long-range forces whose effects will still remain: electromagnetism and gravitation. While we can make clever setups that ensure that the electromagnetic field strength in a region is zero, we cannot do that for gravitation; space cannot be entirely emptied in any real sense in this regard.

Instead of an empty, blank, three-dimensional grid, putting a mass down causes what would have been straight lines to instead become curved by a specific amount. No matter how far away you get from a point mass, the curvature of space never reaches zero, but always remains, even at infinite range.

But even for the electromagnetic force even if you completely zero out the electric and magnetic fields within a region of space theres an experiment you can perform to demonstrate that empty space isnt truly empty. Even if you create a perfect vacuum, devoid of all particles and antiparticles of all types, where the electric and magnetic fields are zero, theres clearly something thats present in this region of what a physicist might call, from a physical perspective, maximum nothingness.

Travel the Universe with astrophysicist Ethan Siegel. Subscribers will get the newsletter every Saturday. All aboard!

All you need to do is place a set of parallel conducting plates in this region of space. Whereas you might expect that the only force theyd experience between them would be gravity, set by their mutual gravitational attraction, what actually winds up happening is that the plates attract by a much greater amount than gravity predicts.

This physical phenomenon is known as the Casimir effect, and was demonstrated to be true by Steve Lamoreaux in 1996: 48 years after it was calculated and proposed by Hendrik Casimir.

The Casimir effect, illustrated here for two parallel conducting plates, excludes certain electromagnetic modes from the interior of the conducting plates while permitting them outside of the plates. As a result, the plates attract, as predicted by Casimir in the 1940s and verified experimentally by Lamoreaux in the 1990s.

Similarly, in 1951, Julian Schwinger, already a co-founder of the quantum field theory that describes electrons and the electromagnetic force, gave a complete theoretical description of how matter could be created from nothing: simply by applying a strong electric field. Although others had proposed the idea back in the 1930s, including Fritz Sauter, Werner Heisenberg, and Hans Euler, Schwinger himself did the heavy lifting to quantify precisely under what conditions this effect should emerge, and henceforth its been primarily known as the Schwinger effect.

Normally, we expect there to be quantum fluctuations in empty space: excitations of any and all quantum fields that may be present. The Heisenberg uncertainty principle dictates that certain quantities cannot be known in tandem to arbitrary precision, and that includes things like:

While we normally express the uncertainty principle in terms of the first two entities, alone, the other applications can have consequences that are equally profound.

This diagram illustrates the inherent uncertainty relation between position and momentum. When one is known more accurately, the other is inherently less able to be known accurately. Every time you accurately measure one, you ensure a greater uncertainty in the corresponding complementary quantity.

Recall that, for any force that exists, we can describe that force in terms of a field: where the force experienced by a particle is its charge multiplied by some property of the field. If a particle passes through a region of space where the field is non-zero, it can experience a force, depending on its charge and (sometimes) its motion. The stronger the field, the greater the force, and the stronger the field, the greater the amount of field energy exists in that particular region of space.

Even in purely empty space, and even in the absence of external fields, there will still be some non-zero amount of field energy that exists in any such region of space. If there are quantum fields everywhere, then simply by Heisenbergs uncertainty principle, for any duration of time that we choose to measure this region over, there will be an inherently uncertain amount of energy present within that region during that time period.

The shorter the time period were looking at, the greater the uncertainty in the amount of energy in that region. Applying this to all allowable quantum states, we can begin to visualize the fluctuating fields, as well as fluctuating particle-antiparticle pairs, that pop in-and-out of existence due to all of the Universes quantum forces.

Even in the vacuum of empty space, devoid of masses, charges, curved space, and any external fields, the laws of nature and the quantum fields underlying them still exist. If you calculate the lowest-energy state, you may find that it is not exactly zero; the zero-point (or vacuum) energy of the Universe appears to be positive and finite, although small.

Now, lets imagine turning up the electric field. Turn it up, higher and higher, and what will happen?

Lets take an easier case first, and imagine theres a specific type of particle already present: a meson. A meson is made of one quark and one antiquark, connected to one another through the strong force and the exchange of gluons. Quarks come in six different flavors: up, down, strange, charm, bottom, and top, while the anti-quarks are simply anti-versions of each of them, with opposite electric charges.

The quark-antiquark pairs within a meson sometimes have opposite charges to one another: either + and - (for up, charm, and top) or + and - (for down, strange, and bottom). If you apply an electric field to such a meson, the positively charged end and the negatively charged end will be pulled in opposite directions. If the field strength is great enough, its possible to pull the quark and antiquark away from one another sufficiently so that new particle-antiparticle pairs are ripped out of the empty space between them. When this occurs, we wind up with two mesons instead of one, with the energy required to create the extra mass (via E = mc) coming from the electric field energy that ripped the meson apart in the first place.

When a meson, such as a charm-anticharm particle shown here, has its two constituent particles pulled apart by too great an amount, it becomes energetically favorable to rip a new (light) quark/antiquark pair out of the vacuum and create two mesons where there was one before. A strong enough electric field, for long-enough lived mesons, can cause this to occur, with the needed energy for creating more massive particles coming from the underlying electric field.

Now, with all of that as background in our minds, lets imagine weve got a very, very strong electric field: stronger than anything we could ever hope to make on Earth. Something so strong that it would be like taking a full Coulomb of charge around ~1019 electrons and protons and condensing each of them into a tiny ball, one purely of positive charge and one purely of negative charge, and separating them by only a meter. The quantum vacuum, in this region of space, is going to be extremely strongly polarized.

Strong polarization means a strong separation between positive and negative charges. If your electric field in a region of space is strong enough, then when you create a virtual particle-antiparticle pair of the lightest charged particle of all (electrons and positrons), you have a finite probability of those pairs being separated by large enough amounts due to the force from the field that they can no longer reannihilate one another. Instead, they become real particles, stealing energy from the underlying electric field in order to keep energy conserved.

As a result, new particle-antiparticle pairs come to exist, and the energy required to make them, from E = mc, reduces the exterior electric field strength by the appropriate amount.

As illustrated here, particle-antiparticle pairs normally pop out of the quantum vacuum as a consequences of Heisenberg uncertainty. In the presence of a strong enough electric field, however, these pairs can be ripped apart in opposite directions, causing them to be unable to reannihilate and forcing them to become real: at the expense of energy from the underlying electric field.

Thats what the Schwinger effect is, and unsurprisingly, its never been observed in a laboratory setting. In fact, the only places where it was theorized to occur was in the highest-energy astrophysical regions to exist in the Universe: in the environments surrounding (or even interior to) black holes and neutron stars. But at the great cosmic distances separating us from even the nearest black holes and neutron stars, even this remains conjecture. The strongest electric fields weve created on Earth are at laser facilities, and even with the strongest, most intense lasers at the shortest pulse times, we still arent even close.

Normally, whenever you have a conducting material, its only the valence electrons that are free to move, contributing to conduction. If you could achieve large enough electric fields, however, you could get all of the electrons to join the flow. In January of 2022, researchers at the University of Manchester were able to leverage an intricate and clever setup involving graphene an incredibly strong material that consists of carbon atoms bound together in geometrically optimal states to achieve this property with relatively small, experimentally accessible magnetic field. In doing so, they also witnesses the Schwinger effect in action: producing the analogue of electron-positron pairs in this quantum system.

Graphene has many fascinating properties, but one of them is a unique electronic band structure. There are conduction bands and valence bands, and they can overlap with zero band gap, enabling both holes and electrons to emerge and flow.

Graphene is an odd material in a lot of ways, and one of those ways is that sheets of it behave effectively as a two-dimensional structure. By reducing the number of (effective) dimensions, many degrees of freedom present in three-dimensional materials are taken away, leaving far fewer options for the quantum particles inside, as well as reducing the set of quantum states available for them to occupy.

Leveraging a graphene-based structure known as a superlattice where multiple layers of materials create periodic structures the authors of this study applied an electric field and induced the very behavior described above: where electrons from not just the highest partially-occupied energy state flow as part of the materials conduction, but where electrons from lower, completely filled bands join the flow as well.

Once this occurs, a lot of exotic behaviors arise in this material, but one was seen for the first time ever: the Schwinger effect. Instead of producing electrons and positrons, it produced electrons and the condensed-matter analogue of positrons: holes, where a missing electron in a lattice flows in the opposite directions to the electron flow. The only way to explain the observed currents were with this additional process of spontaneous production of electrons and holes, and the details of the process agreed with Schwingers predictions from all the way back in 1951.

Atomic and molecular configurations come in a near-infinite number of possible combinations, but the specific combinations found in any material determine its properties. Graphene, which is an individual, single-atom sheet of the material shown here, is the hardest material known to humanity, and in pairs-of-sheets it can create a type of material known as a superlattice, with many intricate and counterintuitive properties.

There are many ways of studying the Universe, and quantum analogue systems where the same mathematics that describes an otherwise inaccessible physical regime applies to a system that can be created and studied in a laboratory are some of the most powerful probes we have of exotic physics. Its very difficult to foresee how the Schwinger effect could be tested in its pure form, but thanks to the extreme properties of graphene, including its ability to withstand spectacularly large electric fields and currents, it arose for the very first time in any form: in this particular quantum system. As coauthor Dr. Roshan Krishna Kumar put it:

When we first saw the spectacular characteristics of our superlattice devices, we thought wow it could be some sort of new superconductivity. Although the response closely resembles those routinely observed in superconductors, we soon found that the puzzling behavior was not superconductivity but rather something in the domain of astrophysics and particle physics. It is curious to see such parallels between distant disciplines.

With electrons and positrons (or holes) being created out of literally nothing, just ripped out of the quantum vacuum by electric fields themselves, its yet another way that the Universe demonstrates the seemingly impossible: we really can make something from absolutely nothing!

Originally posted here:

How the Universe really makes something from nothing - Big Think

The researchers show frequencies of spatially separated clocks can be compared more precisely

The researchers show frequencies of spatially separated clocks can be compared more precisely

An experiment carried out by the University of Oxford researchers combines two unique and one can say even mind-boggling discoveries, namely, high-precision atomic clocks and quantum entanglement, to achieve two atomic clocks that are entangled. This means the inherent uncertainty in measuring their frequencies simultaneously is highly reduced.

While this is a proof-of-concept experiment, it has the potential for use in probing dark matter, precision geodesy and other such applications. The two-node network that they build is extendable to more nodes, the researchers write, in an article on this work published in Nature recently.

Atomic clocks grew in accuracy and became so dependable that in 1967, the definition of a second was revised to be the time taken by 9,19,26,31,770 oscillations of a cesium atom. At the start of the 21st century, the cesium clocks that were available were so accurate that they would gain or lose a second only once in about 20 million years. At present, even this record has been broken and there are optical lattice clocks that are so precise that they lose a second only once in 15 billion years. To give some perspective, that is more than the age of the universe, which is 13.8 billion years.

The more mundane uses to which these clocks can be put include accurate time keeping in GPS, or monitoring stuff remotely on Mars.

If you can measure the frequency difference between these two clocks that are in different locations, that opens up a host of applications, says Raghavendra Srinivas, from the Department of Physics, Clarendon Laboratory, University of Oxford, U.K., who is an author of the Nature paper.

Their work is a proof-of-principle demonstration that two strontium atoms separated in space by a small distance, can be pushed into an entangled state so that a comparison of their frequencies becomes more precise. Potential applications of this when extended in space and including more nodes than two, are in studying the space-time variation of the fundamental constants and probing dark matter deep questions in physics.

In quantum physics, entanglement is a weird phenomenon described as a spooky action at a distance by Albert Einstein. Normally, when you consider two systems separated in space that are also independent and you wished to compare some physical attribute of the two systems, you would make separate measurements of that attribute and this would involve a fundamental limitation to how precisely you can compare the two for two separate measurements have to be made.

On the other hand, if the two were entangled, it is a way of saying that their physical attributes, say spin, or in this case, the frequency, vary in tandem. Measuring the attribute on one system, tells you about the other system. This in turn improves the precision of the measurement to the ultimate limit allowed by quantum theory.

Quantum networks of this kind have been demonstrated earlier, but this is the first demonstration of quantum entanglement of optical atomic clocks.

Dr. Srinivas says, The key development here is that we could improve the fidelity and the rate of this remote entanglement to the point where its actually useful for other applications, like in this clock experiment.

For their demonstration, the researchers used strontium atoms for the ease in generating remote entanglement. They plan to try this with better clocks such as those that use calcium.

We showed that you can now generate remote entanglement in a practical way. At some point, it might be useful for state-of-the art systems, says Dr. Srinivas.

See the rest here:

Using spooky action at a distance to link atomic clocks - The Hindu

UCDs Dr Steve Campbell reflects on the past, present and future of Irelands role in the advancement of quantum technologies.

Many fundamental theories of physics have resulted in important technological revolutions, such as engines and refrigerators from thermodynamics, or modern electronics from electromagnetism.

Recent decades have seen great strides taken in our ability to prepare and manipulate systems such as individual atoms, electrons, or photons which are so small and isolated that they can only be accurately described using quantum mechanics.

Now, the seemingly exotic rules of the quantum world are providing remarkable new opportunities for technological breakthroughs.

In this endeavour, Ireland has a remarkably intimate and grand history. The Irish physicist John Bell provided the fundamental breakthrough to test the veracity of arguably the most counterintuitive aspect of quantum mechanics its inherent non-local character which now lies at the heart of this technological revolution.

Nonlocality refers to the curious fact that, for quantum systems comprised of two or more constituents that have interacted (imagine, for example, two electrons that collided at some point), the act of measuring one of these electrons affects the state of the other, even if they are separated by vast distances.

Bells nonlocality arises from a very fundamental aspect of quantum mechanics concerning how strong correlations can be. Think of a light switch and the bulb it is connected to. In so-called classical physics the world of Newton and Einstein the switch can only be on or off, never anything in between, and the state of the bulb is correlated with the state of the switch.

Quantum mechanics tells us that before we look at the switch, it can exist in a combination (or superposition, in the quantum lingo) of the possibilities. Essentially, it can simultaneously be both on and off. The resulting correlation with the bulb due to this superposition is what we call entanglement.

Once thought to be a fundamental flaw in quantum theory, quantum superposition and entanglement are now established physical phenomena and are ushering in a new wave of devices which utilise these distinctly quantum mechanical effects as resources. These quantum technologies include the most accurate sensors allowed by the laws of physics, unbreakable communication channels and, most excitingly, entirely new paradigms for computation and information processing.

While there has been steady activity in the area of quantum information in Ireland for more than 25 years, recently there has been a significant surge. Driven largely by grassroots activity, supported through national and European funding, virtually every Irish higher education institution is host to an internationally recognised group at the forefront of quantum science and technology.

This has precipitated several major initiatives, such as the establishment of research centres at University College Dublin (UCD) and Tyndall National Institute at University College Cork, and the recently launched MSc in quantum science and technology at Trinity College Dublin, which saw its first cohort of graduates this summer.

These activities feed into the overarching goal to train the next generation of quantum scientists and engineers and to facilitate key knowledge exchange between major industry players with a presence in Ireland, such as IBM, Microsoft, Dell, Google, Intel, homegrown quantum computing enterprise Equal1, and our universities.

The symbiotic relationships being created across these sectors are allowing our researchers to attack a range of exciting challenges from simulating complex molecular dynamics to developing ultraprecise sensors and beyond.

The Irish quantum community is coming together to meet the grand challenge of developing quantum devices. The Irish Research Council, in conjunction with the Shared Island initiative from the Department of An Taoiseach, recently funded EQUITY: ire Strategy for Quantum Information and Technology.

The first activity under this scheme brought together most of Irelands leading scientists in the field, together with major industry representatives, for a two-day workshop to discuss where Ireland stands currently and where we are poised to make an impact.

Several directions are now driving forward including major projects on quantum computing architectures, quantum sensing, and developing a secure quantum communications network. In an age where the protection of our personal data is more important than ever, this last point is highly relevant beyond the ivory tower of academia.

Most of all, EQUITY placed high importance on ensuring that the impact of quantum technologies reached as broad an audience as possible. One step in achieving this goal is with the upcoming Quantum Festival at UCD, where quantum researchers across the whole Island of Ireland will come together to showcase their work.

This event also includes a public lecture by leading quantum securities expert Dr Eleni Diamanti, CNRS research director at the LIP6 Laboratory of Sorbonne University in Paris. In her lecture, Secure communication in a quantum world, Diamanti will explain how the way in which we transmit information is changing thanks to quantum mechanics, what that means for security, and how quantum technologies are poised to impact so many aspects of our lives.

By Dr Steve Campbell

Dr Steve Campbell is a theoretical physicist at the UCD School of Physics and a member of the UCD Centre for Quantum Engineering, Science, and Technology (C-QuEST).

Dr Eleni Diamanti will speak at the UCD Quantum Festival on 29 September. Register for free here.

10 things you need to know direct to your inbox every weekday. Sign up for the Daily Brief, Silicon Republics digest of essential sci-tech news.

Go here to read the rest:

Ireland is gearing up for the next generation of quantum technologies - SiliconRepublic.com

This week, scientists will put the finishing touches on the Zetawatt-Equivalent Ultrashort Pulse Laser System (ZEUS) at the University of Michigan, ushering in a new era in high-powered laser experiments, as reported first byNew Atlas.

The device, touted as the most potentlasersystem in the US, will aid researchers in their study of a variety of phenomena, such as quantum physics, space exploration, and cancer therapy.

(Photo : Marcin Szczepanski, Michigan Engineering)

It is worth noting that the ZEUS laser at theUniversity of Michiganwill serve as the replacement for the 0.5-Petawatt Herculeslaser, which was used to set the Guinness World Record for the Highest Intensity Focused Laser in 2008.

ZEUS is built to replicate a beam approximately a million times more powerful than its maximum strength of 3 Petawatts by aiming its laser towards a high-energy electron beam traveling in the opposite direction.

This full power operation of ZEUS will imitate a zetawatt laser pulse, allowing researchers to study extreme plasmas and explore quantum electrodynamics.

The tests could result in the generation of matter and antimatter that could explain the origins of some of the cosmos' most fundamental phenomena.

"Magnetars, which are neutron stars with extremely strong magnetic fields around them, and objects like active galactic nuclei surrounded by very hot plasma - we can recreate the microphysics of hot plasma in extremely strong fields in the laboratory," ZEUS' Associate Director Louise Willingale said in a statement.

But that kind of operation is not anticipated to happen soon since n ewX-rayimaging technologies will be studied first using low-power laser pulses of 30 terawatts, but 500 terawatt experiments are scheduled for the local fall before starting zetawatt operations in 2023, which is referred to as ZEUS's signature experiment.

Read also:Researchers Use Infrared Laser Light to Wirelessly Transmit Power Over 98 Feet of Thin Air!

In addition to helping scientists understand how materials change over very short periods of time, ZEUS is anticipated to contribute to the development of technologies that enhancenuclear weaponsdetection in shipping materials.

The facility's research could potentially result in more compact and effective particle accelerators that produce radioactive isotopes and proton beams, speeding up the creation of cancer treatments.

Karl Krushelnick, director of the Center for Ultrafast Optical Science, which houses ZEUS, said that it would be among the most powerful laser systems in the world and the highest peak power laser in the US.

The high-repetition target area, which conducts tests with more frequent but lower strength laser pulses, is the first target area of the team to start the system's operation.

Franklin Dollar, a graduate of Michigan who is currently an associate professor of physics and astronomy at the University of California Irvine, is the instrument's first user, and his group is investigating a novel form of X-ray imaging.

They will utilize ZEUS to fire infrared laser pulses into a helium gas target, converting the gas to plasma. By accelerating electrons to high energy, this plasma creates very small X-ray bursts as the electron beams flicker, according to scientists.

Related Article:Laser Coffee? Researchers Create A 'Laser-Powered Extractor' That Pumps Out Cold-Brew 300 Times Faster Than Regular Methods!

This article is owned by Tech Times

Written by Joaquin Victor Tacla

2022 TECHTIMES.com All rights reserved. Do not reproduce without permission.

Excerpt from:

Scientists Will Activate The 'Most Powerful Laser' in the US Later This Week - Tech Times