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Category: quantum physics

Dynamical freezing can protect quantum information for near-cosmic timescales

Preserving quantum information is key to developing useful quantum computing systems. But interacting quantum systems are chaotic and follow laws of thermodynamics, eventually leading to information loss. Physicists have long known of a strange exception, called dynamical freezing, when quantum systems shaken at precisely tuned frequencies evade these laws. But how long can this phenomenon postpone thermodynamics?

Not forever, but for an astonishingly long time, Cornell physicists have determined, giving the first quantitative answer. Using a new mathematical framework, they demonstrate that the frozen state can be stabilized long enough to be a useful strategy for preserving information in quantum systems. This can be a promising route for maintaining coherence in quantum computers as the numbers of qubits scale up to the millions.

“It’s like asking, how do you evade the laws of physics from eventually taking over?” said Debanjan Chowdhury, associate professor of physics in the College of Arts and Sciences. “Imagine that you had a hot cup of coffee that even without a heater, stayed hot. Or a block of ice placed on a heater that never melts. Is that even possible? This has been one of the big open problems in the field of quantum many-body systems.”

Could a niche 80s technology be the key to better quantum computers?

Superconducting computing circuits were briefly heralded as the future of computing in the 1980s. Columnist Karmela Padavic-Callaghan visits a quantum chip foundry where one company is betting this technology’s second act will revolutionise quantum computers.

By Karmela Padavic-Callaghan

The unbearable hardness of deciding about magic

Identifying the boundary between classical and quantum computation is a central challenge in quantum information. In multi-qubit systems, entanglement and magic are the key resources underlying genuinely quantum behaviour. While entanglement is well understood, magic — essential for universal quantum computation — remains relatively poorly characterised. Here we show that determining membership in the stabilizer polytope, which defines the free states of magic-state resource theory, requires super-exponential time $\exp( n^2)$ in the number of qubits $n$, even approximately. We reduce the problem to solving a $3$-SAT instance on $n^2$ variables and, by invoking the exponential time hypothesis, the result follows. As a consequence, both quantifying and certifying magic are fundamentally intractable: any magic monotone for general states must be super-exponentially hard to compute, and deciding whether an operator is a valid magic witness is equally difficult. As a corollary, we establish the robustness of magic as computationally optimal among monotones. This barrier extends even to classically simulable regimes: deciding whether a state lies in the convex hull of states generated by a logarithmic number of non-Clifford gates is also super-exponentially hard. Together, these results reveal intrinsic computational limits on assessing classical simulability, distilling pathological magic states, and ultimately probing and exploiting magic as a quantum resource.

Researchers unlock hidden dimensions inside a single photon

Researchers have discovered new ways to shape quantum light, creating high-dimensional states that can carry much more information per photon. Using advanced tools like on-chip photonics and ultrafast light structuring, they’re pushing quantum communication and imaging into exciting new territory. Although long-distance transmission remains tricky, innovative approaches—such as topological quantum states—could make these fragile signals far more resilient. The momentum suggests quantum optics is entering a bold new phase.

Comments on the Hartle-Hawking state and observers — Ying Zhao

Workshop on quantum aspects of black holes and spacetime.

Topic: Comments on the Hartle-Hawking state and observers.
Speaker: Ying Zhao.
Affiliation: Massachusetts Institute of Technology.
Date: December 3, 2025
Wolfensohn Hall.

It was argued that any fixed holographic theory contains only one closed universe state and hence fails to give semi-classical physics. It was proposed that this problem can be resolved by including a classical observer living inside the universe. Earlier works focused on closed universes connected with asymptotic Euclidean boundaries. In this talk we examine the case of Hartle-Hawking state where the dominant Euclidean topology is a sphere. We show that different features emerge. We comment on the potential implications for the understanding of de Sitter space. Based on work with Daniel Harlow.

Matching vibrations is all it takes to shut down superconductivity in a nearby crystal

The world is never really at rest. Even in a vacuum near ultracold temperatures where all classical motion should come to a halt, you’ll find quantum fluctuations. In thin, two-dimensional materials, these include random vibrations that can alter electromagnetic fields, a feature that theorists have posited could be quite useful for modifying materials.

“It’s a holy grail we’ve been searching for decades,” said Dmitri Basov, Higgins Professor of Physics at Columbia. “We believe we’ve found it.”

In a new paper published in Nature, Basov and 32 collaborators from 17 institutions came together to confirm that quantum fluctuations alone from the vacuum inside atom-thin layers of 2D materials can alter the properties of a larger nearby crystal—a theoretical possibility now experimentally realized for the first time.

New technique spots hidden defects to boost reliability of ultrathin electronics

Future devices will continue to probe the frontier of the very small, and at scales where functionality depends on mere atoms, even the tiniest flaw matters. Researchers at Rice University have shown that hard-to-spot defects in a widely used two-dimensional insulator can trap electrical charges and locally weaken the material, making it more likely to fail at lower voltages. The findings are published in Nano Letters.

“By showing practical ways to detect when and where these defects form, we help make future devices more reliable and repeatable,” said Hae Yeon Lee, an assistant professor of materials science and nanoengineering at Rice, who is a corresponding author on the study.

Building ultrathin electronics such as advanced transistors, photodetectors and quantum devices involves stacking sheets of different 2D materials on top of each other into “heterostructures.” Hexagonal boron nitride (hBN), prized for being atomically flat and chemically stable, is a common building block.

Energy loss triggers quantum thermal Hall-like effect at macroscopic scale

In many quantum materials—materials with unusual electrical and magnetic properties driven by quantum mechanical effects—electrons can organize themselves into Landau levels are essentially quantized energy states that form when charged particles move in a magnetic field.

This process, called Landau quantization, forces electrons into circular (i.e., cyclotron) motion. This motion ultimately produces evenly spaced Landau levels, which are known to underpin various physical phenomena, including the quantum Hall effect.

The quantum Hall effect is a quantum equivalent of the Hall effect that emerges in some two-dimensional (2D) materials at extremely low temperatures and under strong magnetic fields. This effect prompts electrical current to flow along the edges of a material with extremely low loss of energy.

A robust new telecom qubit identified in silicon

Quantum technologies are anticipated to transform computing, communication, and sensing by harnessing the unusual behavior of matter at the atomic scale. Translating quantum’s promise into practical devices will require physical systems that have desirable quantum properties and can be easily manufactured. Silicon, the material behind today’s computer chips, is highly attractive as a platform because it plays to the strengths of the trillion-dollar semiconductor industry that has already been built. Identifying quantum building blocks—qubits—in silicon is, therefore, an important frontier research area.

In a new study, researchers in UC Santa Barbara materials professor Chris Van de Walle’s Computational Materials Group identified a robust new qubit in silicon, called the CN center. The work is published in the journal Physical Review B.

Qubits can be based on atomic-scale defects in a crystal. A prototype example is the NV center, which consists of a nitrogen (N) atom sitting next to a vacancy (V, a missing carbon atom) in a diamond crystal. These defects can interact with both electrons and light, allowing them to emit single photons (quanta of light) that can transmit quantum information or be processed in quantum networks.

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