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We’ve glimpsed something that behaves like a particle of gravity – New Scientist

Have we spotted hints of gravitons?

zf L/Getty Images

Physicists have been searching for gravitons, the hypothetical particles thought to carry gravity, for decades. These have never been detected in space, but graviton-like particles have now been seen in a semiconductor. Using these to understand gravitons behaviour could help unite the general theory of relativity and quantum mechanics, which have long been at odds.

This is a needle in a haystack [finding]. And the paper that started this whole thing is from way back in 1993, says Loren Pfeiffer at Princeton University. He wrote that paper with several colleagues including Aron Pinczuk, who passed away in 2022 before they could find hints of the elusive particles.

Pinczuks students and collaborators, including Pfeiffer, have now completed the experiment the two began discussing 30 years ago. They focused on electrons within a flat piece of the semiconductor gallium arsenide, which they placed in a powerful refrigerator and exposed to a strong magnetic field. Under these conditions, quantum effects make the electrons behave strangely they strongly interact with each other and form an unusual incompressible liquid.

This liquid is not calm but features collective motions where all the electrons move in concert, which can give rise to particle-like excitations. To examine those excitations, the team shined a carefully tuned laser on the semiconductor and analysed the light that scattered off it.

This revealed that the excitation had a kind of quantum spin that has only ever been theorised to exist in gravitons. Though this isnt a graviton per se, it is the closest thing we have seen.

Ziyu Liu at Columbia University in New York who worked on the experiment says he and his colleagues knew that graviton-like excitations could exist in their semiconductor, but it took years to make the experiment precise enough to detect them. From the theoretical side, the story was kind of complete, but in experiments, we were really not sure, he says.

The experiment isnt a true analogue to space-time electrons are confined to a flat, two-dimensional space and move more slowly than objects governed by the theory of relativity.

But it is extremely important and bridges different branches of physics, like the physics of materials and theories of gravity, in a previously underappreciated way, says Kun Yang at Florida State University, who was not involved in the work.

However, Zlatko Papic at the University of Leeds in the UK cautions against equating the new finding with detection of gravitons in space. He says the two are sufficiently equivalent for electron systems like those in the new experiment to become testing grounds for some theories of quantum gravity, but not for every single quantum phenomenon that happens to space-time at cosmic scales.

Connections between this particle-like excitation and theoretical gravitons also raise new ideas about exotic electron states, says team member Lingjie Du at Nanjing University in China.

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ACCESS Allocation Fuels Syracuse University’s Breakthrough in Quantum Physics Theories – HPCwire

March 28, 2024 The description of the Universe includes four fundamental forces the strong and weak interactions that occur at very short-length scales and govern the properties of nuclei, and the forces of electromagnetism and gravity, which act over longer distances. While the first three can be understood using quantum mechanics, gravity is described by a classical theory general relativity.

It has long been a goal of theoretical physics to merge quantum mechanics and general relativity to produce a theory of quantum gravity. Its needed to understand gravity in extreme environments, such as inside black holes and at the earliest instances after the Big Bang.

Syracuse University Physics Professor Simon Catterall recently used an ACCESS allocation on the Expanse supercomputer at the San Diego Supercomputer Center (SDSC) at UC San Diego to simulate a theory of elementary particles that will help scientists better understand quantum gravity. The quantum field theory in question is known as N=4 super Yang-Mills, and the work was carried out in collaboration with Syracuse Graduate Researcher Goksu Can Toga and Renneslauer Polytechnic Institute Professor Joel Giedt.

The super in the name reflects the fact that the theory possesses a supersymmetry that exchanges force-carrying particles like the photon with matter particles like quarks and electrons where every known particle in the standard model has a supersymmetric partner. The force carriers in N=4 super Yang-Mills are similar to the gluons that occur in the theory of nuclear forces the Yang-Mills theory called QCD or quantum chromodynamics.

The remarkable thing is that it is conjectured to be dual, that is equivalent to, a string theory that incorporates Einsteins theory of general relativity at low energies, Catterall said. This duality was postulated by Juan Maldacena of the Institute for Advanced Study in Princeton about 20 years ago and is usually termed the AdSCFT correspondence.

Catterall said that the strange thing about this dual gravitational theory is that it lives in a curved 5-D space called anti-de Sitter space, while the Yang-Mills theory (which does not include gravity) lives at the 4-D boundary of this space. This has led to the alternative name for the AdSCFT correspondence as a holographic duality since all the information on the gravity theory is encoded on the boundary of the space like a hologram.

This idea of a holographic correspondence has generated a huge amount of interest and follow-up work in theoretical physics throughout the world generalizations of this idea have even been used in condensed matter physics to try to explain novel phenomena like high-temperature superconductors, Catterall explained. This conjecture has only been verified in a certain limit of the parameters where certain approximations hold and the goal of our research is to formulate and calculate with the theory everywhere in parameter space using numerical simulation.

Catterall, Can Toga and Giedt have published their results in the Journal of High Energy Physics.

Catteralls research requires the theory to be formulated on a lattice in spacetime, which is very difficult to accomplish without breaking the supersymmetry. However, several research teams including Catteralls group- have solved this discretization problem.

About a decade ago, we were able to formulate the theory, Catterall said. But only in the last two years have we been able to implement simulations of this lattice theory using optimized parallelized code on supercomputers like Expanse at SDSC. We are thus just beginning to truly understand the holographic dualities using these new tools.

Katya Sumwalt, SDSC Communications, contributed to this story.

Source: Kimberly Mann Bruch, SDSC and ACCESS

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Search for decoherence from quantum gravity with atmospheric neutrinos – Nature.com

Department of Physics, Loyola University Chicago, Chicago, IL, USA

R. Abbasi

Deutsches Elektronen-Synchrotron DESY, Zeuthen, Germany

M. Ackermann,S. Athanasiadou,S. Blot,J. Brostean-Kaiser,L. Fischer,T. Karg,M. Kowalski,A. Kumar,N. Lad,C. Lagunas Gualda,S. Mechbal,R. Naab,J. Necker,T. Pernice,S. Reusch,C. Spiering,A. Trettin&J. van Santen

Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand

J. Adams

Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of WisconsinMadison, Madison, WI, USA

S. K. Agarwalla,A. Balagopal V,M. Baricevic,V. Basu,J. Braun,D. Butterfield,S. Chattopadhyay,D. Chirkin,A. Desai,P. Desiati,J. C. Daz-Vlez,H. Dujmovic,M. A. DuVernois,H. Erpenbeck,K. Fang,S. Griffin,F. Halzen,K. Hanson,S. Hori,K. Hoshina,R. Hussain,M. Jacquart,A. Karle,M. Kauer,J. L. Kelley,A. Khatee Zathul,J. Krishnamoorthi,J. P. Lazar,L. Lu,J. Madsen,Y. Makino,S. Mancina,W. Marie Sainte,K. Meagher,R. Morse,M. Moulai,M. Nakos,V. ODell,J. Osborn,J. Peterson,A. Pizzuto,M. Prado Rodriguez,Z. Rechav,B. Riedel,I. Safa,P. Savina,M. Silva,R. Snihur,J. Thwaites,D. Tosi,A. K. Upadhyay,J. Vandenbroucke,J. Veitch-Michaelis,C. Wendt,E. Yildizci,T. Yuan,P. Zilberman&M. Zimmerman

Universit Libre de Bruxelles, Science Faculty, Brussels, Belgium

J. A. Aguilar,N. Chau,I. C. Mari,F. Schlter&S. Toscano

Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

M. Ahlers,K. M. Groth,D. J. Koskinen,T. Kozynets,J. V. Mead,A. Sgaard&T. Stuttard

Department of Physics, TU Dortmund University, Dortmund, Germany

J. M. Alameddine,D. Elssser,P. Gutjahr,M. Hnnefeld,K. Hymon,L. Kardum,W. Rhode,T. Ruhe,J. Soedingrekso,J. Werthebach&L. Witthaus

Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE, USA

N. M. Amin,S. N. Axani,P. A. Evenson,J. G. Gonzalez,R. Koirala,A. Leszczyska,A. Novikov,H. Pandya,E. N. Paudel,A. Rehman,F. G. Schrder,D. Seckel,T. Stanev,S. Tilav&S. Verpoest

Department of Physics, Marquette University, Milwaukee, WI, USA

K. Andeen&A. Vaidyanathan

Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universitt Erlangen-Nrnberg, Erlangen, Germany

G. Anton,A. Domi,A. Eimer,S. Fiedlschuster,T. Glsenkamp,C. Haack,U. Katz,C. Kopper,M. Rongen,S. Schindler,J. Schneider,L. Schumacher&G. Wrede

Department of Physics and Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, MA, USA

C. Argelles,J. Y. Book,K. Carloni,D. Delgado,A. Garcia,M. Jin,N. Kamp,J. P. Lazar,I. Martinez-Soler,I. Safa,B. Skrzypek,W. G. Thompson,A. Y. Wen&P. Zhelnin

Department of Physics and Astronomy, University of Utah, Salt Lake City, UT, USA

Y. Ashida,M. Jeong&C. Rott

III. Physikalisches Institut, RWTH Aachen University, Aachen, Germany

L. Ausborm,C. Benning,J. Bttcher,L. Brusa,S. Deng,S. El Mentawi,P. Frst,E. Ganster,O. Gries,C. Gnther,L. Halve,M. Handt,J. Huler,J. Hermannsgabner,L. Heuermann,O. Janik,S. Latseva,A. Noell,S. Philippen,A. Rifaie,J. Savelberg,M. Schaufel,L. Schlickmann,P. Soldin,M. Thiesmeyer,C. H. Wiebusch&A. Wolf

Physics Department, South Dakota School of Mines and Technology, Rapid City, SD, USA

X. Bai,L. Paul&M. Plum

Department of Physics and Astronomy, University of California, Irvine, CA, USA

S. W. Barwick

Department of Physics, University of California, Berkeley, CA, USA

R. Bay,S. R. Klein,Y. Lyu&S. Robertson

Department of Astronomy, Ohio State University, Columbus, OH, USA

J. J. Beatty,A. Connolly&W. Luszczak

Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH, USA

J. J. Beatty,A. Connolly,W. Luszczak,A. Medina&M. Stamatikos

Fakultt fr Physik & Astronomie, Ruhr-Universitt Bochum, Bochum, Germany

J. Becker Tjus,A. Franckowiak,J. Hellrung,E. Kun,M. Lincetto,L. Merten,P. Reichherzer&G. Sommani

Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden

J. Beise,O. Botner,A. Coleman,C. Glaser,T. Glsenkamp,A. Hallgren,N. Heyer,E. OSullivan,C. Prez de los Heros,A. Pontn&N. Valtonen-Mattila

Physik-department, Technische Universitt Mnchen, Garching, Germany

C. Bellenghi,P. Eller,M. Ha Minh,M. Karl,T. Kontrimas,E. Manao,R. Orsoe,E. Resconi,L. Ruohan,C. Spannfellner,A. Terliuk&M. Wolf

Department of Physics and Astronomy, University of Rochester, Rochester, NY, USA

S. BenZvi&S. Griswold

Department of Physics, University of Maryland, College Park, MD, USA

D. Berley,E. Blaufuss,B. A. Clark,J. Evans,K. L. Fan,S. J. Gray,K. D. Hoffman,M. J. Larson,A. Olivas,R. Procter-Murphy,T. Schmidt,S. Sclafani,G. W. Sullivan&A. Vijai

Dipartimento di Fisica e Astronomia Galileo Galilei, Universit Degli Studi di Padova, Padova, Italy

E. Bernardini,C. Boscolo Meneguolo&S. Mancina

Department of Physics and Astronomy, University of Kansas, Lawrence, KS, USA

D. Z. Besson,M. Seikh&R. Young

Karlsruhe Institute of Technology, Institute for Astroparticle Physics, Karlsruhe, Germany

F. Bontempo,R. Engel,A. Haungs,W. Hou,T. Huber,D. Kang,P. Koundal,T. Mukherjee,P. Sampathkumar,H. Schieler,F. G. Schrder,R. Turcotte,M. Venugopal,A. Weindl&M. Weyrauch

Institute of Physics, University of Mainz, Mainz, Germany

S. Bser,T. Ehrhardt,D. Kappesser,L. Kpke,E. Lohfink,Y. Popovych&J. Rack-Helleis

School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, Atlanta, GA, USA

B. Brinson,C. Chen,P. Dave,I. Taboada&C. F. Tung

Department of Physics, University of Adelaide, Adelaide, South Australia, Australia

R. T. Burley,E. G. Carnie-Bronca,G. C. Hill&E. J. Roberts

Institut fr Kernphysik, Westflische Wilhelms-Universitt Mnster, Mnster, Germany

R. S. Busse,M. Dittmer,A. Kappes,C. J. Lozano Mariscal,M. Neumann,B. Schlter,M. A. Unland Elorrieta&J. Vara

Department of Physics, Drexel University, Philadelphia, PA, USA

M. A. Campana,X. Kang,M. Kovacevich,N. Kurahashi,C. Love&R. Shah

Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA

Z. Chen,H. Hamdaoui,J. Kiryluk&Z. Zhang

Department of Physics, Sungkyunkwan University, Suwon, Republic of Korea

S. Choi,S. In,W. Kang,J. W. Lee,S. Rodan,G. Roellinghoff,C. Rott&C. Tnnis

Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA

G. H. Collin,J. M. Conrad,A. Diaz,J. Hardin,D. Vannerom&P. Weigel

Vrije Universiteit Brussel (VUB), Dienst ELEM, Brussels, Belgium

P. Coppin,P. Correa,C. De Clercq,K. D. de Vries,E. Magnus,Y. Merckx&N. van Eijndhoven

Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA, USA

D. F. Cowen,D. Fox,Y. Liu&Y. Wang

Department of Physics, Pennsylvania State University, University Park, PA, USA

D. F. Cowen,K. Leonard DeHolton,Y. Liu,Y. Wang&J. Weldert

Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL, USA

J. J. DeLaunay,A. Ghadimi,M. Marsee,M. Santander&D. R. Williams

Oskar Klein Centre and Department of Physics, Stockholm University, Stockholm, Sweden

K. Deoskar,C. Finley,A. Hidvegi,K. Hultqvist,M. Jansson&C. Walck

Centre for Cosmology, Particle Physics and PhenomenologyCP3, Universit catholique de Louvain, Louvain-la-Neuve, Belgium

G. de Wasseige,K. Kruiswijk,M. Lamoureux,C. Raab&M. Vereecken

Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA

T. DeYoung,D. Grant,R. Halliday,A. A. Harnisch,A. Kochocki,E. Krupczak,K. B. M. Mahn,F. Mayhew,J. Micallef,H. Niederhausen,M. U. Nisa,S. C. Nowicki,B. Pries,D. Salazar-Gallegos,S. E. Sanchez Herrera,K. Tollefson,J. P. Twagirayezu,C. Weaver,N. Whitehorn&S. Yu

Department of Physics, University of Wuppertal, Wuppertal, Germany

E. Ellinger,K. Helbing,S. Hickford,F. Lauber,U. Naumann,A. Sandrock,N. Schmeisser&T. Strwald

Karlsruhe Institute of Technology, Institute of Experimental Particle Physics, Karlsruhe, Germany

R. Engel,J. Saffer,S. Shefali&D. Soldin

Department of Physics and The International Center for Hadron Astrophysics, Chiba University, Chiba, Japan

K. Farrag,C. Hill,A. Ishihara,M. Meier,Y. Morii,R. Nagai,A. Obertacke Pollmann,A. Rosted,N. Shimizu&S. Yoshida

Department of Physics, Southern University, Baton Rouge, LA, USA

A. R. Fazely,J. Mitchell,S. Ter-Antonyan,K. Upshaw&X. W. Xu

Institute of Physics, Academia Sinica, Taipei, Taiwan

A. Fedynitch

Institut fr Physik, Humboldt-Universitt zu Berlin, Berlin, Germany

N. Feigl,H. Kolanoski&M. Kowalski

Department of Astronomy, University of WisconsinMadison, Madison, WI, USA

J. Gallagher

Lawrence Berkeley National Laboratory, Berkeley, CA, USA

L. Gerhardt,S. R. Klein,Y. Lyu,G. T. Przybylski,S. Robertson&T. Stezelberger

Department of Physics, Chung-Ang University, Seoul, Korea

C. Ha

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Search for decoherence from quantum gravity with atmospheric neutrinos - Nature.com

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Scientists made the coldest large molecule on record and it has a super strange chemical bond – Livescience.com

Scientists recently created a never-before-seen four-atom molecule the coldest of its kind ever made.

Researchers created the oddball molecule a strange configuration of sodium-potassium with an ultralong chemical bond at 134 nanokelvin, or just 134 billionths of a degree above absolute zero. They described the ultracold material Jan. 31 in the journal Nature.

Ultracold systems are crucial to understand quantum behavior because quantum mechanics, the rules governing subatomic particles, dominate at low temperatures. These setups also let scientists precisely control the energy of particles to create quantum simulations, which model other quantum systems with physics we don't fully understand. For instance, studying the quantum behavior in a system of ultracold molecules could one day help scientists identify the material properties needed in high-temperature superconductors.

Related: Inside the 20-year quest to unravel the bizarre realm of 'quantum superchemistry'

The problem is that there's an inherent tradeoff: an ultracold system that is too simple may not capture the full array of behavior in interesting quantum systems. But add more complexity, and designing an effective experiment gets trickier.

"Usually people use atoms or ions and what makes them somewhat controllable is the fact that you have a relatively limited number of quantum states," Roman Bause, a quantum optics researcher at the University of Groningen in the Netherlands, told Live Science.

"But if I draw all the quantum states of a molecule, it will fill quite a thick book. It's a factor of a million or so more states."

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All these additional quantum states open up more interesting quantum questions, but also make the molecules difficult to cool.

To solve that problem, in the new study, Tao Shi, a physicist at the Chinese Academy of Sciences, and international collaborators used a multi-step cooling process, beginning with laser cooling to create the record-breaking molecules.

Related: How do lasers work?

This cooling method uses laser beams fired from all directions at a moving atom. The atom absorbs light and enters an excited quantum state, then immediately releases energy to return to its ground state. But, because of how the atom is moving relative to the laser beams (known as the Doppler effect), the atom releases a little more energy than it absorbs, cooling itself.

"The problem with using this technique for molecules is that there's not just one ground state. You would potentially need thousands of laser beams and it's just too much technical effort," Bause said.

However, ultracold atoms are an excellent starting point to build ultracold molecules. Using a mixture of ultracold sodium (Na) and potassium (K) atoms, Shi's team weakly associated these single particles into diatomic NaK molecules.

This is where the technical difficulties really started. "The problem with associating cold atoms is you heat them while doing this so then you need another cooling technique, evaporative cooling," Bause said.

For reasons no one quite understands, under these cooling conditions the molecules stick together and the experimenter can no longer precisely control them. This particular challenge has stumped researchers across the field for years.

But, by shining in precisely controlled microwaves, Shi's team overcame the clumping issue in the diatomic NaK molecules as they were cooled down to 134 nanokelvin.

The microwaves also had a unique advantage when getting the two NaK molecules to weakly associate and form one four-atom-molecule of (NaK)2. "If you shape the microwaves exactly right, what you have is a potential that's not just repulsive at short ranges but it's also attractive at longer ranges," Bause said.

As such, this first-of-its-kind four-atom molecule has a central bond 1000 times longer than the bond between the sodium and potassium atoms and was created at a temperature more than 3000 times colder than any previous four-atom molecule.

The new finds are exciting because they "will ultimately bring us to interesting places where we currently have no theoretical handle high temperature superconductors and materials for better lithium batteries for example," Bause said.

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Scientists made the coldest large molecule on record and it has a super strange chemical bond - Livescience.com

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The Casimir Effect: Unlocking a Mind-Boggling Part of Reality – Popular Mechanics

Hendrik Casimirs idea for an experiment was simple: bring two metallic objects extremely close together and wait. Spontaneously, as if by magic, the objects will be drawn together. No external forces, no pushes or pulls, no action of gravity or tension or

This landmark experiment, first devised by Casimir just after World War IIand only realized 25 years agopaved the way for scientists to witness the manifestations of quantum theory in a real, practical way. Quantum fields and their vibrations power our modern-day understanding of physics, from subatomic interactions to the evolution of the entire universe. And what we learned, thanks to Casimirs work, is that infinite energy permeates the vacuum of space. There are many ideas in the science fiction universe that propose using vacuum energy to power a starship or other advanced kind of propulsion, like a warp drive. While these ideas are still dreams, the fact remains that a simple experiment, devised in 1948, set fire to our imaginations and our understanding of the universe.

Casimir, a Dutch physicist, had spent his graduate years with his advisor, Niels Bohr, one of the godfathers of quantum physics, and had picked up a liking for this new, extraordinary theory of the cosmos. But as quantum theory evolved, it started to make extremely strange statements about the universe. The quantum world is weird, and its ultimate weirdness is normally invisible to us, operating at scales well below our normal human perception or experimentation. Casimir started to wonder how we might be able to test those ideas.

He went on to discover a clever way to measure the effects of ever-present infinite quantum fields merely using bits of metal held extremely close together. His work showed that quantum behavior can manifest in surprising ways that we can measure. It also showed that the strangeness of quantum behavior is real and cant be ignored, and what quantum mechanics says about the workings of the universeno matter how bizarremust be believed.

One of the lessons of the quantum world is that particles, like electrons, photons, neutrinos, and whatnot, arent what they seem to be. Instead, each of the particles that we see in nature is actually just a piece of a much larger, grander entity. These grander entities are known as quantum fields, and the fields soak every bit of space and timeall throughout the universethe same way that oil and vinegar soaks a piece of bread.

There is a quantum field for every kind of particle: one field for the electrons, one for the photons, and so on. These fields are invisible to us, but they make up the fundamental building blocks of existence. They are constantly vibrating and buzzing. When the fields vibrate with enough energy, particles appear. When the fields die down, the particles disappear. Another way to look at this is to say that what we call a particle is really a localized vibration of a quantum field. When two particles interact, its really just two pieces of quantum fields interacting with each other.

These quantum fields are always vibrating, even when those vibrations arent strong enough to produce a particle. If you take a box and empty out all of the stuffall the electrons, all the photons, all the neutrinos, all the everythingthe box is still filled with these quantum fields. Since those fields vibrate even in isolation, that means the box is filled with invisible vacuum energy, also known as zero-point energythe energy of these fundamental vibrations.

In fact, you can calculate how many vibrations are in each of these quantum fields ... and the answer is infinity! There are small ones, medium ones, big ones, and gigantic ones, all flopping on top of each other continuously, as if spacetime itself was boiling at the subatomic level. This means that the vacuum of the universe really is made of something. Theres no such thing as a true vacuum; wherever you go, there are always vibrating quantum fields.

This is where Casimirs experiment comes in: If you take two metal plates and stick them really, really close together, the quantum fields between those plates must behave in a certain way: the wavelengths of their vibrations must fit perfectly between the plates, just like the vibrations on a guitar string have to fit their wavelengths to the length of the string. In the quantum case, there are still an infinite number of vibrations between the plates, butand this is crucialthere are not as many infinite vibrations between the plates as there are outside the plates.

How does this make sense? In mathematics, not all infinities are the same, and weve developed clever tools to be able to compare them. For example, consider one kind of infinity where you add successive numbers to each other. You start with 1, then add 2, then add 3, then add 4, and so on. If you keep that addition going forever, youll reach infinity. Now consider another kind of addition, this one involving powers of 10. You start with 101, then add to it 102, then 103, then 104, and keep going.

Casimirs experiment brings two metallic objects extremely close together. The objects will be drawn together because of vibrations in the quantum field and no other force.

Again, if you keep this series going on forever, youll also reach infinity. But in a sense youll get to infinity faster. So by carefully subtracting these two sequences, you can get a measure of their difference even though they both go to infinity.

Using this clever bit of mathematics, we can subtract the two kinds of infinitiesthe ones between the metal plates and the ones outsideand arrive at a finite number. This means that there really are more quantum vibrations outside the two plates than there are inside the plates. This phenomenon leads to the conclusion that the quantum fields outside the plates push the two plates together, something called the Casimir effect in Hendriks honor.

The effect is incredibly small, roughly 10-12 Newtons, and it requires the metal plates to be within a micrometer of each other. (One Newton is the force which accelerates an object of 1 kilogram by 1 meter per second squared.) So, even though Casimir could predict the existence of this quantum effect, it wasnt until 1997 that we were finally able to measure it, thanks to the efforts of Yale physicist Steve Lamoreaux.

Quantum Physics In Action

Perhaps most strangely, the creature with the deepest connection to the fundamental quantum nature of the universe is the gecko. Geckos have the ability to walk on walls, and even upside-down on ceilings. To accomplish this feat, a geckos limbs are covered in countless, microscopic hair-like fibers. These fibers get close enough to the molecules of the surface it wants to climb on for the Casimir effect to take action. It creates an attractive force between the hair and the surface. Each individual hair provides only an extremely tiny amount of force, but all the hairs combined are enough to support the gecko.

In this experimental setup, which can fit on a kitchen countertop, the plates dont magically pull themselves together. Instead its the infinite vibrating quantum fields of spacetime pushing them together from the outside.

We dont normally see or sense or experience the Casimir effect. But when we want to design micro- and nano-scale machines, we have to account for these additional forces. For example, researchers have designed micro-scale sensors that can monitor the flow of chemicals on a molecule-by-molecule basis, but the Casimir effect can disrupt the operations of this sensor if we didnt know about it.

For several years, researchers have been investigating the possibility that we really can extract vacuum energy and use it for energy. A 2002 patent was awarded for a device that captures the electric charge from the Casimir experimental setups two metal plates, charging a storage battery. The device can be used as a generator. To continuously generate power a plurality of metal plates are fixed around a core and rotated like a gyrocompass, according to the patent.

The U.S. Defense Departments Defense Advanced Research Projects Agency (DARPA) gave researchers $10 million in 2009 to pursue a better understanding of the Casimir force. Though progress in actually using vacuum energy continues to be incremental, this line of energy research could give rise to innovations in nanotechnology, such as building a device capable of levitation, researchers said at the time.

At the University of Colorado in Boulder, Garret Moddels research group has developed devices that produce power that appears to result from zero-point energy quantum fluctuations, according to the groups website. Their device essentially recreates Casimirs experiment, generating an electrical current between the two metal layers that researchers could measure, despite applying no electrical voltage.

As for Casimir himself, who was immersed in a quantum revolution unfolding at Leiden University, he had a tendency to downplay the importance of his own work. In his autobiography, Haphazard Reality, Casimir said, The story of my own life is of no particular interest. And his monumental 1948 paper designing his experiment ends with the simple statement, Although the effect is small, an experimental confirmation seems not infeasable and might be of a certain interest.

In fact, his initial insight did not make a big splash on the scientific community, nor were there glowing popular press accounts of his experiment. Part of the reason was Casimirs own modesty, and another is that he soon left academic research to pursue a career in industry. But despite these humble beginnings, his work cannot be understated.

Today, we continue to refine Casimirs original experimental setup, searching for any cracks in our theories, and we use it as a foundation to explore ever more deeply the fundamental nature of the cosmos.

Paul M. Sutter is a science educator and a theoretical cosmologist at the Institute for Advanced Computational Science at Stony Brook University and the author of How to Die in Space: A Journey Through Dangerous Astrophysical Phenomena and Your Place in the Universe: Understanding Our Big, Messy Existence. Sutter is also the host of various science programs, and hes on social media. Check out his Ask a Spaceman podcast and his YouTube page.

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The Casimir Effect: Unlocking a Mind-Boggling Part of Reality - Popular Mechanics

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Study reveals quantum effect possibly linked to unproven ‘graviton’ particle – Anadolu Agency | English

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Study reveals quantum effect possibly linked to unproven 'graviton' particle - Anadolu Agency | English

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Scientists are searching for quantum gravity at the South Pole – Cosmos

Scientists are going to extreme lengths and places to try and understand the fundamental nature of the universe.

Physics as we know it doesnt seem to agree with itself. Gravity and quantum mechanics are two pillars of modern physics, but they dont gel well together. One theory which suggests that there is a way of marrying the two worlds of physics is called quantum gravity.

Today, classical physics describes the phenomena in our normal surroundings such as gravity, while the atomic world can only be described using quantum mechanics, says Tom Stuttard from the University of Copenhagens Neils Bohr Institute (NBI). The unification of quantum theory and gravitation remains one of the most outstanding challenges in fundamental physics. It would be very satisfying if we could contribute to that end.

Stuttard is co-author of a paper published in Nature Physics which suggests that neutrino data from the IceCube Neutrino Observatory at the South Pole might be used to find evidence for quantum gravity.

More than 300,000 neutrinos have been studied at IceCube. These arent neutrinos from outer space, but those created in Earths atmosphere.

Looking at neutrinos originating from the Earths atmosphere has the practical advantage that they are by far more common than their siblings from outer space. We needed data from many neutrinos to validate our methodology. This has been accomplished now. We are ready to enter the next phase in which we will study neutrinos from deep space, Stuttard explains.

Neutrinos are sometimes called ghost particles because they have no electrical charge and are nearly massless, meaning they dont interact with the electromagnetic field or the nuclei of atoms. They can travel billions of lightyears through the universe largely unbothered.

If the neutrino undergoes the subtle changes that we suspect, this would be the first strong evidence of quantum gravity, says Stuttard.

While the search hasnt yielded results that suggest the existence of quantum gravity yet, Stuttard and his colleagues remain hopeful. Their top priority has been to prove that experiments could one day prove the existence of quantum gravity.

For years, many physicists doubted whether experiments could ever hope to test quantum gravity. Our analysis shows that it is indeed possible, and with future measurements with astrophysical neutrinos, as well as more precise detectors being built in the coming decade, we hope to finally answer this fundamental question, Stuttard says.

Future experiments which look at neutrinos from space, rather than atmospheric neutrinos, could answer the question once and for all.

While we did have hopes of seeing changes related to quantum gravity, the fact that we didnt see them does not exclude at all that they are real, Stuttard notes. When an atmospheric neutrino is detected at the Antarctic facility, it will typically have travelled through the Earth. Meaning approximately 12,700 km a very short distance compared to neutrinos originating in the distant universe. Apparently, a much longer distance is needed for quantum gravity to make an impact, if it exists.

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Scientists are searching for quantum gravity at the South Pole - Cosmos

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If quantum gravity exists, scientists think they’ll find it at the South Pole – Earth.com

In the realm of physics, one of the most perplexing questions revolves around the existence of quantum gravity. A team of scientists has embarked on a pioneering study, utilizing data from thousands of neutrino sensors near the South Pole, to unravel this mystery.

Their findings, recently published in the prestigious journal Nature Physics, shed light on the potential to unite the two distinct worlds of physics: classical and quantum mechanics.

Tom Stuttard, Assistant Professor at the Niels Bohr Institute (NBI), University of Copenhagen, is part of the team that has contributed to developing a method that exploits neutrino data to reveal the existence of quantum gravity.

If as we believe, quantum gravity does indeed exist, this will contribute to unite the current two worlds in physics. Today, classical physics describes the phenomena in our normal surroundings such as gravity, while the atomic world can only be described using quantum mechanics, Stuttard explains.

The unification of quantum theory and gravitation remains one of the most outstanding challenges in fundamental physics. It would be very satisfying if we could contribute to that end, he said.

The study, a collaboration between the NBI team and American colleagues, analyzed more than 300,000 neutrinos. However, these neutrinos were not the most intriguing type originating from deep space sources.

Instead, they were created in the Earths atmosphere when high-energy particles from space collided with nitrogen or other molecules.

Looking at neutrinos originating from the Earths atmosphere has the practical advantage that they are by far more common than their siblings from outer space, Stuttard notes.

We needed data from many neutrinos to validate our methodology. This has been accomplished now. Thus, we are ready to enter the next phase in which we will study neutrinos from deep space, he continued.

The study was conducted using data from the IceCube Neutrino Observatory, situated next to the Amundsen-Scott South Pole Station in Antarctica.

Unlike most other astronomy and astrophysics facilities, IceCube works best for observing space on the opposite side of the Earth, specifically the Northern hemisphere.

This is because while neutrinos can easily penetrate our planet, including its hot, dense core, other particles are stopped. This results in a much cleaner signal for neutrinos coming from the Northern hemisphere.

Neutrinos are unique particles with no electrical charge and nearly no mass, allowing them to travel billions of light-years through the Universe in their original state, undisturbed by electromagnetic and strong nuclear forces.

The key question the team is exploring is whether the properties of neutrinos remain completely unchanged as they travel over vast distances or if subtle changes can be detected.

If the neutrino undergoes the subtle changes that we suspect, this would be the first strong evidence of quantum gravity, Stuttard emphasizes.

To understand the changes in neutrino properties that the team is searching for, it is essential to grasp some background information.

While referred to as a particle, what we observe as a neutrino is actually three particles produced together, known in quantum mechanics as superposition.

The neutrino can have three fundamental configurations, or flavors: electron, muon, and tau.

The observed configuration changes as the neutrino travels, a peculiar phenomenon known as neutrino oscillations. This quantum behavior, referred to as quantum coherence, is maintained over thousands of kilometers or more.

In most experiments, the coherence is soon broken. But this is not believed to be caused by quantum gravity. It is just very difficult to create perfect conditions in a lab, Stuttard explains.

In contrast, neutrinos are special in that they are simply not affected by matter around them, so we know that if coherence is broken it will not be due to shortcomings in the human-made experimental setup, he continued.

When asked about the expectations for the studys results, Stuttard admitted, We find ourselves in a rare category of science projects, namely experiments for which no established theoretical framework exists. Thus, we just did not know what to expect. However, we knew that we could search for some of the general properties we might expect a quantum theory of gravity to have.

Whilst we did have hopes of seeing changes related to quantum gravity, the fact that we didnt see them does not exclude at all that they are real, Stuttard clarifies.

When an atmospheric neutrino is detected at the Antarctic facility, it will typically have travelled through the Earth. Meaning approximately 12,700 km a very short distance compared to neutrinos originating in the distant Universe. Apparently, a much longer distance is needed for quantum gravity to make an impact, if it exists, Stuttard continued.

The studys top goal was to establish the methodology for detecting quantum gravity. For years, many physicists doubted whether experiments could ever hope to test quantum gravity. Our analysis shows that it is indeed possible, and with future measurements with astrophysical neutrinos, as well as more precise detectors being built in the coming decade, we hope to finally answer this fundamental question, Stuttard concludes.

In summary, this important study led by Tom Stuttard and his colleagues marks a significant milestone in the quest to unravel the mysteries of quantum gravity. By establishing a methodology to detect quantum gravity using neutrino data, the team has opened up new avenues for future research.

As scientists continue to study neutrinos from deep space and develop more precise detectors in the coming years, they inch closer to answering one of the most fundamental questions in physics.

This study brings us closer to understanding the elusive nature of quantum gravity and holds the potential to bridge the gap between the two distinct worlds of classical and quantum mechanics, ultimately leading to a more unified understanding of our universe.

The full study was published in the journal Nature Physics.

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If quantum gravity exists, scientists think they'll find it at the South Pole - Earth.com

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Physicists make record-breaking ‘quantum vortex’ to study the mysteries of black holes – Livescience.com

Scientists have created a giant quantum tornado inside a helium superfluid, and they want to use it to probe the enigmatic nature of black holes.

The whirlpool made from liquid helium cooled to near absolute zero moves without friction, making it mimic the way rotating black holes warp the space-time that surrounds them.

By studying the vortex, physicists could glean important insight into the behavior of the cosmic monsters. The researchers published their findings March 20 in the journal Nature.

"Using superfluid helium has allowed us to study tiny surface waves in greater detail and accuracy than with our previous experiments in water," lead author Patrik Svancara, a physicist at the University of Nottingham in the U.K., said in a statement. "As the viscosity of superfluid helium is extremely small, we were able to meticulously investigate their interaction with the superfluid tornado and compare the findings with our own theoretical projections."

Related: Supermassive black hole at the heart of the Milky Way is approaching the cosmic speed limit, dragging space-time along with it

The workings of black holes remain a persistent mystery for physicists. The known laws of physics break in the presence of these extreme objects' infinite gravitational pulls. For those looking to combine Einstein's theory of general relativity with quantum mechanics, this means black holes' warping of space-time offers an alluring pull.

In the absence of a cataclysmic space-time rupture on Earth, the team behind the new study looked to a model system that could simulate some of the extreme eddies that exist around black holes. After supercooling liquid helium to a few fractions above absolute zero, they placed it inside a tank with a propeller at the bottom to stir up a vortex inside the fluid.

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Then, by watching how the superfluid (which flows roughly 500 times more easily than water) moved, the researchers observed how thousands of tiny vortices inside it combined into a giant whirlpool.

"Superfluid helium contains tiny objects called quantum vortices, which tend to spread apart from each other," Svancara said in the statement. "In our set-up, we've managed to confine tens of thousands of these quanta in a compact object resembling a small tornado, achieving a vortex flow with record-breaking strength in the realm of quantum fluids."

By studying the quantum whirlpool, the scientists found convincing similarities to how black holes behave in space. Most notably, they observed a similar black hole phenomenon called ringdown, which is when a newly merged black hole wobbles on its axis.

Now that the simpler parallels have been observed, the researchers will train their experiment on more mysterious aspects of black hole behavior.

This "could eventually lead us to predict how quantum fields behave in curved spacetimes around astrophysical black holes," co-author Silke Weinfurtner, a professor of physics at the University of Nottingham, said in the statement.

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Physicists make record-breaking 'quantum vortex' to study the mysteries of black holes - Livescience.com

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Chinese-led team finds first evidence of particles behaving like gravitons – South China Morning Post

Our work has shown the first experimental substantiation of gravitons in condensed matter since the elusive particle was conceptualised in the 1930s, the studys lead author Du Lingjie from Nanjing University told state news agency Xinhua on Thursday.

The graviton is a bridge connecting quantum mechanics and general relativity theory. If confirmed, it will have huge implications for modern physics research, he said.

02:01

Worlds deepest laboratory opens in southwest China in search of dark matter

Worlds deepest laboratory opens in southwest China in search of dark matter

The study was highly collaborative, according to the paper. Researchers at Princeton University prepared high-quality semiconductor samples, while the experiment was carried out at a unique facility that took Du and his team three years to build.

In Albert Einsteins theory of general relativity, he described gravity as space-time distortions caused by mass and energy.

Such a theory, which explains gravity beautifully at a large scale, poses challenges in quantum mechanics, which governs the universe at the smallest scale.

As a result, the graviton was proposed as a particle dedicated to carrying gravity. If it existed, a graviton should be massless and travel at the speed of light except that, so far, gravitons have never been observed in space.

How the toy that stumped Einstein is inspiring a Chinese search for clean energy

When Du was a postdoctoral researcher at Columbia University in 2019, his team discovered a special excitation phenomenon in quantum materials that led theoretical physicists to think it could point to the detection of gravitons.

However, the requirements for conducting such experiments were high. The system needed to be placed in a powerful refrigerator where temperatures are near absolute zero, and exposed to a magnetic field 100,000 times stronger than the Earths average magnetic field.

Some requirements could even appear contradictory. For instance, we have to install windows on the refrigerator to make optical measurements, but the windows can cause the systems temperature to [easily rise], paper co-author Liang Jiehui, of Nanjing University, told Xinhua.

Du spoke to Xinhua about working in the teams home-developed facility. Working at minus 273.1 degrees Celsius, a special microscope like this can capture particle excitations as weak as 10 gigahertz and determine their spin, he said.

The researchers used a flat sheet of gallium arsenide semiconductor, which when subjected to low temperature and a magnetic field showed a phenomenon called the quantum Hall effect.

Electrons in the semiconductor started to interact with each other and moved in a highly organised fashion, like a liquid.

Chinese researchers hope to create real AI scientists

The team then shone a finely-tuned laser onto the material to study the potential excitation of the electrons. They found the electrons were doing a so-called type-2 quantum spin, which would only exist in gravitons.

They then measured the momentum and energy of the electrons, and confirmed evidence for them to behave in a graviton-like way.

It took us three years to build the experimental device. It was very challenging and we made it, Du said.

We look forward to using it to continue the hunt for gravitons. Hopefully, it will lead to more cutting-edge discoveries at the quantum frontier, Du said.

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Chinese-led team finds first evidence of particles behaving like gravitons - South China Morning Post

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