A new method verifies that a quantum state is entangled when only a limited or suboptimal set of measurements are experimentally accessible, providing an efficient way to verify entanglement in real-world scenarios.
Category: quantum physics
Twisted WSe₂ reveals elusive charge-neutral quantum modes
Quantum materials, materials with properties that are influenced by the laws of quantum mechanics, have attracted considerable attention over the past few decades. Their unique properties make these materials advantageous for the development of numerous cutting-edge technologies, including quantum computers, highly sensitive sensors and energy-efficient electronics.
In some quantum materials, electrons strongly interact with each other, producing what are known as correlated quantum phases, states in which the behavior of individual electrons is influenced by the behavior of other electrons. These phases can give rise to desirable properties or effects, including superconductivity, magnetism and collective excitations.
Researchers at University at California at Santa Barbara recently observed charge-neutral propagating collective spin-valley modes, coordinated waves of quantum behavior that carry no electrical charge and are difficult to probe experimentally, in the two-dimensional (2D) semiconductor twisted tungsten diselenide (WSe2).
Prototype sets record for optical quantum information technology
Chinese scientists have developed a programmable quantum computing prototype called Jiuzhang 4.0 that has set a new world record for optical quantum information technology, according to a study published May 13 in the journal Nature.
Led by the University of Science and Technology of China (USTC), the team used the prototype to solve the Gaussian boson sampling problem at a speed more than 1054 times that of the world’s most powerful supercomputer, the study said.
The researchers said they manipulated and detected quantum states of up to 3,050 photons —a significant leap from the 255 photons achieved with the previous Jiuzhang 3.0.
Roadmap charts three paths to room-temperature quantum materials for cooler computing
Imagine a laptop that never gets hot, a phone that holds its charge for days, or a computer memory chip designed to permanently retain data, even when the power goes out. This is the possibility sitting inside a remarkable family of materials that a team of researchers from the University of Ottawa and the Massachusetts Institute of Technology (MIT) has spent years trying to understand, and they just published a comprehensive roadmap of the field to date in the journal Newton.
Magnetic topological materials sit at the crossroads of magnetism and topology in modern physics. Topology is the mathematical study of shapes that cannot be continuously deformed into one another. In these materials, that idea protects the flow of electrons in a way that normal materials simply cannot.
“Magnetic topological materials offer a unique platform where magnetism and quantum physics work together in ways we are only beginning to fully understand,” explains Hang Chi, Canada Research Chair in Quantum Electronic Devices and Circuits and Assistant Professor at uOttawa’s Department of Physics. “This review brings together the field’s most significant advances and gives researchers a shared foundation to build on.”
Jacob Barandes — “A New Formulation of Quantum Theory”
Talk by Jacob Barandes (Harvard University)
Seminar Website: https://harvardfop.jacobbarandes.com/
YouTube Channel: / @foundationsofphysicsharvard.
Foundations of Physics @Harvard Seminar Series.
April 12, 2023.
Abstract: In this talk, I will present a novel, exact correspondence between stochastic-process theory and quantum theory. On the one hand, this stochastic-quantum correspondence means that one can use the Hilbert-space tools of quantum theory to model real-world stochastic processes beyond the usual Markov approximation, generalizing previous stochastic approaches to quantum theory as well as potentially opening up new applications for quantum simulators and quantum computers. On the other hand, the stochastic-quantum correspondence implies that one can replace the instrumentalist textbook axioms of quantum theory with much more physically transparent axioms. The result is a clearer physical picture underlying quantum theory that is consistent with the standard no-go theorems, helps clarify the meaning of signature features of quantum theory like interference and entanglement, and has potential implications for addressing the measurement problem.
Experimental quantum kernel trick with nuclear spins in a solid
Kusumoto, T., Mitarai, K., Fujii, K. et al. Experimental quantum kernel trick with nuclear spins in a solid. npj Quantum Inf 7, 94 (2021). https://doi.org/10.1038/s41534-021-00423-0
Designing better quantum circuits with AI
Researchers from the group of theoretical physicist Hans Briegel have collaborated with NVIDIA to develop an AI method that automatically generates efficient quantum circuits, a key bottleneck in making quantum computers practically useful.
The work was published in Machine Learning: Science and Technology, in a paper titled “Synthesis of discrete–continuous quantum circuits with multimodal diffusion models.”
Before a quantum computer can perform any useful task, a quantum algorithm needs to be translated into a sequence of elementary quantum operations, known as quantum gates. Writing these quantum circuits efficiently is one of the hardest open problems in the field.
Dr. Stuart Hameroff: Consciousness is More than Computation!
13 years ago, I walked into Dr. Stuart Hameroff’s operating room with a camera, a microphone, and a single stubborn question:
Is consciousness computation?
Hameroff, an anesthesiologist and professor at the University of Arizona, and co-author with Sir Roger Penrose of the Orch OR theory, said no.
Emphatically. Unfashionably. Against the entire weight of mainstream neuroscience and Silicon Valley orthodoxy.
At the GF2045 conference, where I first met him, Ray Kurzweil went out of his way to declare Orch OR “totally wrong.” Others called it speculative. Untestable. Unscientific.
Today, in the age of large language models, that argument is no longer a niche dispute among philosophers and physicists. It is the decisive question of our century.
Scientists found a way to cool quantum computers using noise
Quantum computers only work when they are kept extremely cold. The problem is that today’s cooling systems also create noise, which can interfere with the fragile quantum information they are supposed to protect. Researchers at Chalmers University of Technology in Sweden have now introduced a new type of minimal quantum “refrigerator” that turns this challenge into an advantage. Instead of fighting noise, the device partially relies on it to operate. The result is highly precise control over heat and energy flow, which could help make large scale quantum technology possible.
Quantum technology is widely expected to reshape major areas of society. Potential applications include drug discovery, artificial intelligence, logistics optimization, and secure communications. Despite this promise, serious technical barriers still stand in the way of real world use. One of the most difficult challenges is maintaining and controlling the delicate quantum states that make these systems work.