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Category: quantum physics – Page 33
Could Metasurfaces Be The Next Quantum Information Processors?
In the race toward practical quantum computers and networks, photons — fundamental particles of light — hold intriguing possibilities as fast carriers of information at room temperature. Photons are typically controlled and coaxed into quantum states via waveguides on extended microchips, or through bulky devices built from lenses, mirrors, and beam splitters. The photons become entangled – enabling them to encode and process quantum information in parallel – through complex networks of these optical components. But such systems are notoriously difficult to scale up due to the large numbers and imperfections of parts required to do any meaningful computation or networking.
Could all those optical components could be collapsed into a single, flat, ultra-thin array of subwavelength elements that control light in the exact same way, but with far fewer fabricated parts?
Optics researchers in the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) did just that. The research team led by Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, created specially designed metasurfaces — flat devices etched with nanoscale light-manipulating patterns — to act as ultra-thin upgrades for quantum-optical chips and setups.
Researchers blend theoretical insight and precision experiments to entangle photons on an ultra-thin chip.
Scientists achieve direct measurement of quantum metric tensor in black phosphorus
Quantum distance refers to a measure of quantum mechanical similarity between two quantum states. A quantum distance of one means that the two quantum states are the same, whereas a quantum distance of zero implies that they are exactly the opposite. Physicists introduced this concept in the realm of theoretical science a long time ago, but its importance has been increasingly recognized in the field of physics only in recent times.
In the last few years, many experimental physicists have tried to measure the quantum distance of electrons in real solid-state materials, but a direct measurement of the quantum distance and thus quantum metric tensor—a key geometric quantity in modern physics defined in terms of the distance between nearby quantum states—has remained elusive so far.
Since the quantum metric tensor is highly relevant in explaining and understanding fundamental physical phenomena in solids, it is, therefore, crucial to come up with an effective methodology for its direct measurement in solid-state systems.
Quantum Breakthrough: Scientists Find “Backdoor” to 60-Year-Old Superconducting Mystery
A Copenhagen team has unlocked a clever “backdoor” into studying rare quantum states once thought beyond reach.
Scientists at the Niels Bohr Institute, University of Copenhagen, have discovered a new approach for investigating rare quantum states that occur within superconducting vortices. These states were first proposed in the 1960s, but confirming their existence has proven extremely challenging because they occur at energy levels too small for most experiments to detect directly.
This breakthrough was achieved through a mix of creative problem-solving and the advanced development of custom-made materials in the Niels Bohr Institute’s laboratories. The research findings have been published in Physical Review Letters.
New work achieves a pure quantum state without the need for cooling
Three nano-glass spheres cling to one another. They form a tower-like cluster, similar to when you pile three scoops of ice cream on top of one another—only much smaller. The diameter of the nano cluster is ten times smaller than that of a human hair.
With the help of an optical device and laser beams, researchers at ETH Zurich have succeeded in keeping such objects almost completely motionless in levitation. This is significant when it comes to the future development of quantum sensors, which, together with quantum computers, constitute the most promising applications of quantum research.
The team’s work appears in Nature Physics.
Researchers discover universal rules of quantum entanglement across all dimensions
A team of theoretical researchers used thermal effective theory to demonstrate that quantum entanglement follows universal rules across all dimensions. Their study was published online in Physical Review Letters.
“This study is the first example of applying thermal effective theory to quantum information. The results of this study demonstrate the usefulness of this approach, and we hope to further develop this approach to gain a deeper understanding of quantum entanglement structures,” said lead author and Kyushu University Institute for Advanced Study Associate Professor Yuya Kusuki.
In classical physics, two particles that are far apart behave independently. However, in quantum physics, two particles can exhibit strong correlations regardless of the distance between them. This quantum correlation is known as quantum entanglement.
‘Neglected’ particles that could rescue quantum computing
One of the most promising approaches to overcoming this challenge is topological quantum computing, which aims to protect quantum information by encoding it in the geometric properties of exotic particles called anyons. These particles, predicted to exist in certain two-dimensional materials, are expected to be far more resistant to noise and interference than conventional qubits.
“Among the leading candidates for building such a computer are Ising anyons, which are already being intensely investigated in condensed matter labs due to their potential realization in exotic systems like the fractional quantum Hall state and topological superconductors,” said Aaron Lauda, professor of mathematics, physics and astronomy at the USC Dornsife College of Letters, Arts and Sciences and the study’s senior author. “On their own, Ising anyons can’t perform all the operations needed for a general-purpose quantum computer. The computations they support rely on ‘braiding,’ physically moving anyons around one another to carry out quantum logic. For Ising anyons, this braiding only enables a limited set of operations known as Clifford gates, which fall short of the full power required for universal quantum computing.”
But in a new study published in Nature Communications, a team of mathematicians and physicists led by USC researchers has demonstrated a surprising workaround. By adding a single new type of anyon, which was previously discarded in traditional approaches to topological quantum computation, the team shows that Ising anyons can be made universal, capable of performing any quantum computation through braiding alone. The team dubbed these rescued particles “neglectons,” a name that reflects both their overlooked status and their newfound importance. This new anyon emerges naturally from a broader mathematical framework and provides exactly the missing ingredient needed to complete the computational toolkit.
Heavy fermions entangled: Discovery of Planckian time limit opens doors to novel quantum technologies
A joint research team from Japan has observed “heavy fermions,” electrons with dramatically enhanced mass, exhibiting quantum entanglement governed by the Planckian time—the fundamental unit of time in quantum mechanics. This discovery opens up exciting possibilities for harnessing this phenomenon in solid-state materials to develop a new type of quantum computer. The findings are published in npj Quantum Materials.
Heavy fermions arise when conduction electrons in a solid interact strongly with localized magnetic electrons, effectively increasing their mass. This phenomenon leads to unusual properties like unconventional superconductivity and is a central theme in condensed matter physics. Cerium-rhodium-tin (CeRhSn), the material studied in this research, belongs to a class of heavy fermion systems with a quasi-kagome lattice structure, known for its geometrical frustration effects.
Researchers investigated the electronic state of CeRhSn, known for exhibiting non-Fermi liquid behavior at relatively high temperatures. Precise measurements of CeRhSn’s reflectance spectra revealed non-Fermi liquid behavior persisting up to near room temperature, with heavy electron lifetimes approaching the Planckian limit. The observed spectral behavior, describable by a single function, strongly indicates that heavy electrons in CeRhSn are quantum entangled.
