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The inside of the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider. Rochester physicists working at the detector have observed spin entanglement between top quarks and top antiquarks persisting at long distances and high speeds. Credit: CERN

Physicists have demonstrated quantum entanglement in top quarks and their antimatter partners, a discovery made at CERN. This finding extends the behavior of entangled particles to distances beyond the reach of light-speed communication and opens new avenues for exploring quantum mechanics at high energies.

An experiment by a group of physicists led by University of Rochester physics professor Regina Demina has produced a significant result related to quantum entanglementan effect that Albert Einstein called spooky action at a distance.

Entanglement concerns the coordinated behavior of minuscule particles that have interacted but then moved apart. Measuring propertieslike position or momentum or spinof one of the separated pair of particles instantaneously changes the results of the other particle, no matter how far the second particle has drifted from its twin. In effect, the state of one entangled particle, or qubit, is inseparable from the other.

Quantum entanglement has been observed between stable particles, such as photons or electrons.

But Demina and her group broke new ground in that they found, for the first time, entanglement to persist between unstable top quarks and their antimatter partners at distances farther than what can be covered by information transferred at the speed of light. Specifically, the researchers observed spin correlation between the particles.

Hence, the particles demonstrated what Einstein described as spooky action at a distance.

The finding was reported by the Compact Muon Solenoid (CMS) Collaboration at the European Center for Nuclear Research, or CERN, where the experiment was conducted.

Confirming the quantum entanglement between the heaviest fundamental particles, the top quarks, has opened up a new avenue to explore the quantum nature of our world at energies far beyond what is accessible, the report read.

CERN, located near Geneva, Switzerland, is the worlds largest particle physics laboratory. Production of top quarks requires very high energies accessible at the Large Hadron Collider (LHC), which enables scientists to send high-energy particles spinning around a 17-mile underground track at close to the speed of light.

The phenomenon of entanglement has become the foundation of a burgeoning field of quantum information science that has broad implications in areas like cryptography and quantum computing.

Top quarks, each as heavy as an atom of gold, can only be produced at colliders, such as LHC, and thus are unlikely to be used to build a quantum computer. But studies like those conducted by Demina and her group can shed light on how long entanglement persists, whether it is passed on to the particles daughters or decay products, and what, if anything, ultimately breaks the entanglement.

Theorists believe that the universe was in an entangled state after its initial fast expansion stage. The new result observed by Demina and her researchers could help scientists understand what led to the loss of the quantum connection in our world.

Demina recorded a video for CMS social media channels to explain her groups result. She used the analogy of an indecisive king of a distant land, whom she called King Top.

King Top gets word that his country is being invaded, so he sends messengers to tell all the people of his land to prepare to defend. But then, Demina explains in the video, he changes his mind and sends messengers to order the people to stand down.

He keeps flip flopping like this, and nobody knows what his decision will be at the next moment, Demina says.

Nobody, Demina goes on to explain, except the leader of one village in this kingdom who is known as Anti-Top.

They know each others state of mind at any moment in time, Demina says.

Deminas research group consists of herself and graduate student Alan Herrera and postdoctoral fellow Otto Hindrichs.

As a graduate student, Demina was on the team that discovered the top quark in 1995. Later, as a faculty member at Rochester, Demina co-led a team of scientists from across the US that built a tracking device that played a key role in the 2012 discovery of the Higgs bosonan elementary particle that helps explains the origin of mass in the universe.

Rochester researchers have a long history at CERN as part of the CMS Collaboration, which brings together physicists from around the globe. Recently, another Rochester team achieved a significant milestone in measuring the electroweak mixing angle, a crucial component of the Standard Model of Particle Physics, which explains how the building blocks of matter interact.

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Faster Than the Speed of Light: Information Transfer Through Spooky Action at a Distance at the Large Hadron Collider - SciTechDaily

Jun 24 2024Reviewed by Lexie Corner

In a studypublished in PeerJ Computer Science, Professor Kazuhiro Ogataand Assistant Professor Canh Minh Do of the Japan Advanced Institute of Science and Technology (JAIST) suggested using symbolic model checking to validate quantum circuits.

Quantum computing is a fast-developing technology that utilizes the principles of quantum physics to tackle complicated computational problems that are extremely difficult for classical computing.

To take advantage of quantum computing, researchers worldwide have created a large number of quantum algorithms that show notable gains over classical algorithms.

Creating these algorithms requires the use of quantum circuits, which are models of quantum processing. Before they are actually deployed on quantum hardware, they are utilized to design and implement quantum algorithms.

Quantum circuits consist of a series of quantum gates, measurements, and qubit initializations, among other events. Quantum gates execute quantum computations by working on qubits, the quantum equivalents of conventional bits (0s and 1s), and manipulating the system's quantum states.

Quantum states are the output of quantum circuits that can be monitored to provide classical outcomes with probabilities from which additional actions can be taken. Since quantum computing is frequently counterintuitive and substantially distinct from classical computing, the likelihood of mistakes is significantly larger. As a result, it is critical to ensure that quantum circuits have the correct features and perform as planned.

This can be accomplished using model checking, a formal verification approach used to ensure that systems meet desirable attributes. Although certain model checkers are specialized to quantum programs, there is a distinction between model-checking quantum programs and quantum circuits due to differences in representation and the absence of iterations in quantum circuits.

Considering the success of model-checking methods for verification of classical circuits, model-checking of quantum circuits is a promising approach. We developed a symbolic approach for model checking of quantum circuits using laws of quantum mechanics and basic matrix operations using the Maude programming language.

Canh Minh Do, Assistant Professor, Japan Advanced Institute of Science and Technology

Maude is a high-level specification/programming language based on rewriting logic that enables the formal definition and verification of complicated systems. It comes with a Linear Temporal Logic (LTL) model checker that determines if systems meet the necessary features. Maude also enables the development of exact mathematical models of systems.

Using the Dirac notation and the rules of quantum physics, the researchers formally defined quantum circuits in Maude as a set of quantum gates and measurement applications. They provided the systems intended attributes and its initial state in LTL.

By using a set of quantum physics laws and basic matrix operations formalized in our specifications, quantum computation can be reasoned in Maude.The researchers then automatically checked whether quantum circuits satisfied the required characteristics using the integrated Maude LTL model checker.

Using this method, several early quantum communication protocols, each with increasing complexity, were checked: Superdense Coding, Quantum Teleportation, Quantum Secret Sharing, Entanglement Swapping, Quantum Gate Teleportation, Two Mirror-image Teleportation, and Quantum Network Coding.

They discovered that the initial iteration did not meet the desired property of Quantum Gate Teleportation. By employing this method, the researchers suggested an updated version and verified that it was accurate.

These findings highlight the significance of the suggested novel technique for the verification of quantum circuits. However, the researchers highlight certain drawbacks of their strategy that need more investigation.

Dr. Do added, In the future, we aim to extend our symbolic reasoning to handle more quantum gates and more complicated reasoning on complex number operations. We also would like to apply our symbolic approach to model-checking quantum programs and quantum cryptography protocols.

Verifying the expected functionality of quantum circuits will be extremely useful in the approaching era of quantum computing. In this context, the current technique is the first step toward a broader framework for verifying and specifying quantum circuits, opening the way for error-free quantum computing.

The study was supported by JST SICORP Grant Number JPMJSC20C2, Japan, and JSPS KAKENHI Grant Numbers JP23H03370, JP23K19959, and JP24K20757.

Do, C. M., etal. (2024) Symbolic model checking quantum circuits in Maude. PeerJ Computer Science. doi:10.7717/peerj-cs.2098

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The Road to Error-Free Quantum Computing - AZoQuantum

Time May Actually Be One Big IllusionJuana Mari Moya - Getty Images

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Could the observable universe be exclusively composed of layered, mutually entangled systems?

The passage of time puzzles quantum physicists, who seek to fit it into a cohesive model.

One wild theory posits that time visibly passes because were entangled with... well... everything.

Time has puzzled scientists for many decades. Does it meaningfully exist apart from our experience of it as everything moves toward the disintegration of entropy along its irrefutable arrow? You cant put the spilled milk of the weirdness of time back in the jug.

In new research published in the American Physical Society's peer-reviewed journal Physical Review A, scientists from Italy (led by Alessandro Coppo) try to translate one theory of time into real lifeor, at least, closer to it. The theory is called Page and Wootters mechanism, and Coppo has studied it for years. Its a quantum mechanics idea that dates back to 1983.

While general relativity (in the classical physics model) lets time be a variablelike the perception-dependent difference between time on Earth and time in space in stories like Interstellarquantum physics requires it to be nailed down. That means instead of a dependent variable (something defined by an external property, like local gravity or an objects distance from Earth), time must be independent, and there must be some way to measure it as such.

This may seem counterintuitive. After all, quantum mechanics is considered the newer version of thingsthe one that destabilizes the foundation of physics in order to be reconciled with the classical model. But time has a unique role in quantum systems. After all, everything in a particular time, defined in some objective way, is knitted together through quantum interactions until it forms a capture of the entire universe (if you zoom out enough).

In their paper, Coppo and his coauthors turn the Page and Wootters approach into a real concept for a clock. Within quantum physics, a clock isnt much like the one you wear on your wrist or hang in your officeits anything that has a predictable and uniform behavior that can be used as a measurement. (For example, this 2021 Quanta article lists increasingly stinky garbage as a kind of clock!)

New Scientist explains that Page and Wootters wondered if our world is so quantumly entangled within itself that any visible passing of time is a symptom of entanglement. They also suggested that we ourselves are implicated in that entanglement just by seeing the passage of timebecause someone outside of the entangled system would see it standing still. The clock, therefore, is the item within the entangled system that shows time passing.

Its easy to see why this theory has stayed mostly abstract for over 40 years. To turn it into something with measurements based in real life observation, scientists took iconic physics equations and restricted them to conditions that match the Page and Wootters scenario. They considered two systems that are entangled but do not interact, where one system is a harmonic oscillatorlike a quartz timing in a watch, or a pendulum.

Their solution may prove to be consistent within classical and quantum mechanics, because when enough particles are placed into each quantum systemwhen it reaches the threshold called macroscopic, based on massthe systems align with classical physics as well.

Thats a big dealif our entire, very macroscopic world fits into this definition of time based on entanglement, it means everything around us is entangled. Things would need to be entangled almost by definition in order to be part of our observable world. And it would mean that anything we see where time passes (no matter how far away it is) is linked with us in a vital way.

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Time May Actually Be One Big Illusion, Says a New Study - AOL

In 1948, Dutch physicist Hendrik Casimirwho worked with one of the fathers of quantum physics, Neils Bohrdeveloped an ingenious experiment to witness the invisible (at least, to us) wonders of quantum mechanics. Casimir placed two electrically neutral plates within one micrometer of each other in a vacuum. Without any forces acting upon them, you might expect the plates to remain perfectly still but they didnt. Instead, the plates were pulled together via the invisible quantum fluctuations that permeate spacetime.

This experiment was a stunning display of the invisible quantum world, and this phenomenon became known, quite rightly, as the Casimir effect. Itd be another 50 years before the Yale physicist Steve Lamoreaux finally measured this incredibly small effect, but with the rise of nanotechnology during that same period, understanding the Casimir effect and how it would impact these incredibly small machines became vitally important. Sort of how the designs of satellites need to take our understanding of relativity into account, so too must nanotechnologies be designed with the Casimir effect in mind.

Now, in the next step toward understanding this incredible phenomenon, scientists from the Chinese Academy of Sciences have found a method of tuning this effect. Using a ferrofluida fluid that can be manipulated using magnetic fieldsas an intermediate medium, the researchers used magnetic fields to create a reversible transition from Casimir attraction to repulsion. The results of the study were published in late May in the journal Nature Physics.

The quantum fluctuation-induced Casimir force can be either attractive or repulsive, depending on the dielectric permittivities [the ability of a substance to store electrical energy in an electric field] and magnetic permeabilities of the materials involved, the paper reads. Our theoretical calculations predict that, by varying the magnetic field, separation distance and ferrofluid volume fraction, the Casimir force can be tuned from attractive to repulsive over a wide range of parameters in this system.

As the paper notes, its challenging to alter the dielectric permittivities of a material, but you can manipulate the permeabilities of ferrofluids with magnetic fields. This is how the researchers designed an experiment examining this kind of manipulation between a gold sphere and a silicon dioxide substrate. As predicted, the experiment allowed the researchers to accurately manipulate the Casimir attraction or repulsion of the two materials.

Gaining some kind of control over this incredibly small effect could have big implications for the creation of future nano- and micro-electromechanical devices. Of course, there are other ideas surrounding the Casimir effectalso known as vacuum energy or zero-point energyespecially as it plays a role in studying the black hole-based Hawking radiation that features prominently in discussions about warp bubbles and warp drives. But for now, its very large technological impact mostly pertains to the world of very small machines.

Darren lives in Portland, has a cat, and writes/edits about sci-fi and how our world works. You can find his previous stuff at Gizmodo and Paste if you look hard enough.

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Scientists Discovered How to Control the Casimir Effectand Supercharge Tiny Machines - Popular Mechanics