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Category: quantum physics – Page 293

Unitary collapse of Schrodinger’s cat state

Unitary collapse of Schrödinger’s cat state https://journals.aps.org/pra/abstract/10.1103/PhysRevA.110.L030202

Schrödinger’s cat, that iconic thought experiment where a cat in a box is both alive and dead until someone peeks.

The authors study a system composed of a single qubit coupled to a soft-mode quantum oscillator. They show that spontaneous unitary evolution of this system create a Schr\ odinger-cat-like state of the oscillator, which is subsequently lost in a sudden process strongly resembling the measurement-induced collapse of wave function.

Symmetry Spotted in Statistical Mechanics

The identification of a new type of symmetry in statistical mechanics could help scientists derive and interpret fundamental relationships in this branch of physics.

Symmetry is a foundational concept in physics, describing properties that remain unchanged under transformations such as rotation and translation. Recognizing these invariances, whether intuitively or through complex mathematics, has been pivotal in developing classical mechanics, the theory of relativity, and quantum mechanics. For example, the celebrated standard model of particle physics is built on such symmetry principles. Now Matthias Schmidt and colleagues at the University of Bayreuth, Germany, have identified a new type of invariance in statistical mechanics (the theoretical framework that connects the collective behavior of particles to their microscopic interactions) [1]. With this discovery, the researchers offer a unifying perspective on subtle relationships between observable properties and provide a general approach for deriving new relations.

The concept of conserved, or time-invariant, properties has roots in ancient philosophy and was crucial to the rise of modern science in the 17th century. Energy conservation became a cornerstone of thermodynamics in the 19th century, when engineers uncovered the link between heat and work. Another important type of invariance is Galilean invariance, which states that the laws of physics are identical in all reference frames moving at a constant velocity relative to each other, resulting in specific relations between positions and velocities in different frames. Its extension, Lorentz invariance, posits that the speed of light is independent of the reference frame. Einstein’s special relativity is based on Lorentz invariance, while his general relativity broadens the idea to all coordinate transformations. These final examples illustrate that invariance not only provides relations between physical observables but can shape our understanding of space, time, and other basic concepts.

Quantum-inspired design boosts efficiency of heat-to-electricity conversion

Researchers at Rice University have found a new way to improve a key element of thermophotovoltaic (TPV) systems, which convert heat into electricity via light. Using an unconventional approach inspired by quantum physics, Rice engineer Gururaj Naik and his team have designed a thermal emitter that can deliver high efficiencies within practical design parameters.

The research could inform the development of thermal-energy electrical storage, which holds promise as an affordable, grid-scale alternative to batteries. More broadly, efficient TPV technologies could facilitate renewable energy growth—an essential component of the transition to a net-zero world. Another major benefit of better TPV systems is recouping from industrial processes, making them more sustainable. To put this in context, up to 20–50% of the heat used to transform raw materials into consumer goods ends up being wasted, costing the United States economy over $200 billion annually.

TPV systems involve two main components: photovoltaic (PV) cells that convert light into electricity and thermal emitters that turn heat into light. Both of these components have to work well in order for the system to be efficient, but efforts to optimize them have focused more on the PV cell.

Photon qubits challenge AI, enabling more accurate quantum computing without error-correction techniques

In an era where AI and data are driving the scientific revolution, quantum computing technology is emerging as another game-changer in the development of new drugs and new materials.

Dr. Hyang-Tag Lim’s research team at the Center for Quantum Technology at the Korea Institute of Science and Technology (KIST) has implemented a quantum computing algorithm that can estimate interatomic bond distances and ground state energies with chemical accuracy using fewer resources than conventional methods, and has succeeded in performing accurate calculations without the need for additional quantum error mitigation techniques.

The work is published in the journal Science Advances.

Using matter waves, scientists unveil novel collective behaviors in quantum optics

A research team led by Dominik Schneble, Ph.D., Professor in the Department of Physics and Astronomy, has uncovered a novel regime, or set of conditions within a system, for cooperative radiative phenomena, casting new light on a 70-year-old problem in quantum optics.

Their findings on previously unseen collective spontaneous emission effects, in an array of synthetic (artificial) atoms, are published in Nature Physics, accompanied by a theoretical paper in Physical Review Research.

Spontaneous emission is a phenomenon in which an excited atom falls to a lower-energy state and spontaneously emits a quantum of electromagnetic radiation in the form of a single . When a single excited atom decays and emits a photon, the probability of finding the atom in its falls exponentially to zero as time progresses.

Korean Scientists Achieve Unprecedented Real-Time Capture of Quantum Information

DGIST and UNIST researchers have discovered a new quantum state, the exciton-Floquet synthesis state, enabling real-time quantum information control in two-dimensional semiconductors.

A research team led by Professor Jaedong Lee from the Department of Chemical Physics at DGIST (President Kunwoo Lee) has unveiled a groundbreaking quantum state and an innovative mechanism for extracting and manipulating quantum information through exciton and Floquet states.

Collaborating with Professor Noejung Park from UNIST’s Department of Physics (President Chongrae Park), the team has, for the first time, demonstrated the formation and synthesis process of exciton and Floquet states, which arise from light-matter interactions in two-dimensional semiconductors. This study captures quantum information in real-time as it unfolds through entanglement, offering valuable insights into the exciton formation process in these materials, thereby advancing quantum information technology.

AlphaQubit tackles one of quantum computing’s biggest challenges

AlphaQubit: an AI-based system that can more accurately identify errors inside quantum computers.

AlphaQubit is a neural-network based decoder drawing on Transformers, a deep learning architecture developed at Google that underpins many of today’s large language models. Using the consistency checks as an input, its task is to correctly predict whether the logical qubit — when measured at the end of the experiment — has flipped from how it was prepared.

We began by training our model to decode the data from a set of 49 qubits inside a Sycamore quantum processor, the central computational unit of the quantum computer. To teach AlphaQubit the general decoding problem, we used a quantum simulator to generate hundreds of millions of examples across a variety of settings and error levels. Then we finetuned AlphaQubit for a specific decoding task by giving it thousands of experimental samples from a particular Sycamore processor.

When tested on new Sycamore data, AlphaQubit set a new standard for accuracy when compared with the previous leading decoders. In the largest Sycamore experiments, AlphaQubit makes 6% fewer errors than tensor network methods, which are highly accurate but impractically slow. AlphaQubit also makes 30% fewer errors than correlated matching, an accurate decoder that is fast enough to scale.

Physicists think they may know the key to unlocking time travel

Imagine a thread so thin it’s invisible to the naked eye but packed with the mass of thousands of stars. This isn’t science fiction—it’s the theoretical description of cosmic strings, structures that may hold answers to the Universe’s greatest mysteries. If confirmed, researchers believe these theoretical strings could unlock the key to time travel.

Cosmic strings, if they exist, are thought to be incredibly slender. Some say they’d be long tubes, either stretching infinitely or looping back on themselves. Despite their thinness, a cosmic string’s mass could rival tens of thousands of stars, and it would gradually shrink over time, radiating gravitational waves as it “wiggles.”

Physicists have proposed two types of cosmic strings thus far. The first, “cosmic superstrings,” stems from string theory, a framework suggesting the Universe’s fundamental particles are vibrating strings. Superstrings could be stretched across the cosmos, providing clues about the fabric of reality and possibly holding the key to time travel, too.

Time may be an illusion, new study finds

Researchers propose that time is a result of quantum entanglement, the mysterious connection between particles separated by vast distances. Their findings, published in the journal Physical Review A, could offer a clue to solving the problem of time.

“There exists a way to introduce time which is consistent with both classical laws and quantum laws, and is a manifestation of entanglement,” explained Alessandro Coppo, a physicist at the National Research Council of Italy and the study’s lead author. “The correlation between the clock and the system creates the emergence of time, a fundamental ingredient in our lives.”

In quantum mechanics, time is a fixed phenomenon, an unchanging flow from past to present. It remains external to the ever-changing quantum systems it measures and can only be observed through changes in external entities, like the hands of a clock.

Experiment suggests quantum computers can coordinate actions of moving devices

New research from the University of Kent has demonstrated that quantum information could eventually be used to coordinate the actions of devices that can move, such as drones or autonomous vehicles. This could lead to more efficient logistics, which could make deliveries cheaper, and better use of limited bandwidth for the likes of self-driving cars.

By carrying out “real world” experiments on a quantum computer, the team of quantum physicists (led by Ph.D. student Josh Tucker in the University of Kent’s School of Physics and Astronomy), found that if the two devices share a pair of quantum coins (), the devices can continue to influence each other even after they have been separated and can no longer communicate.

The experiments simulated the phenomenon using real qubits inside a quantum computer developed by IBM. The qubits are made of superconducting material and kept at temperatures colder than the interstellar void. This allows them to behave according to the laws of quantum physics that defy common sense—including the ability to influence each other without coming into contact and without sending signals.

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