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Category: quantum physics

A New Ingredient for Quantum Error Correction

Entanglement and so-called magic states have long been viewed as the key resources for quantum error correction. Now contextuality, a hallmark of quantum theory, joins them as a complementary resource.

Machines make mistakes, and as they scale up, so too do the opportunities for error. Quantum computers are no exception; in fact, their errors are especially frequent and difficult to control. This fragility has long been a central obstacle to building large-scale devices capable of practical, universal quantum computation. Quantum error correction attempts to circumvent this obstacle, not by eliminating sources of error but by encoding quantum information in such a way that errors can be detected and corrected as they occur [1]. In doing so, the approach enables fault-tolerant quantum computation. Over the past few decades, researchers have learned that this robustness relies on intrinsically quantum resources, most notably, entanglement [2] and, more recently, so-called magic states [3].

Superfluids are supposed to flow indefinitely. Physicists just watched one stop moving

Ordinary matter, when cooled, transitions from a gas into a liquid. Cool it further still, and it freezes into a solid. Quantum matter, however, can behave very differently. In the early 20th century, researchers discovered that when helium is cooled, it transitions from a seemingly ordinary gas into a so-called superfluid. Superfluids flow without losing any energy, among other quantum quirks, like an ability to climb out of containers.

What happens when you cool a superfluid down even more? The answer to this question has eluded physicists since they first started asking it half a century ago.

Quantum batteries could quadruple qubit capacity while reducing energy infrastructure requirements

Scientists have unveiled a new approach to powering quantum computers using quantum batteries—a breakthrough that could make future computers faster, more reliable, and more energy efficient.

Quantum computers rely on the rules of quantum physics to solve problems that could transform computing, medicine, energy, finance, communications, and many other fields in the years ahead.

But sustaining their delicate quantum states typically requires room-sized, energy-intensive cryogenic cooling systems, as well as a system of room-temperature electronics.

New light-based platform sets the stage for future quantum supercomputers

A light has emerged at the end of the tunnel in the long pursuit of developing quantum computers, which are expected to radically reduce the time needed to perform some complex calculations from thousands of years down to a matter of hours.

A team led by Stanford physicists has developed a new type of “optical cavity” that can efficiently collect single photons, the fundamental particle of light, from single atoms. These atoms act as the building blocks of a quantum computer by storing “qubits”—the quantum version of a normal computer’s bits of zeros and ones. This work enables that process for all qubits simultaneously, for the first time.

In a study published in Nature, the researchers describe an array of 40 cavities containing 40 individual atom qubits as well as a prototype with more than 500 cavities. The findings indicate a way to ultimately create a million-qubit quantum computer network.

New ABF crystal delivers high-performance vacuum ultraviolet nonlinear optical conversion

Vacuum ultraviolet (VUV, 100–200 nm) light sources are indispensable for advanced spectroscopy, quantum research, and semiconductor lithography. Although second harmonic generation (SHG) using nonlinear optical (NLO) crystals is one of the simplest and most efficient methods for generating VUV light, the scarcity of suitable NLO crystals has long been a bottleneck.

To address this problem, a research team led by Prof. Pan Shilie at the Xinjiang Technical Institute of Physics and Chemistry of the Chinese Academy of Sciences (CAS) has developed the fluorooxoborate crystal NH4B4O6F (ABF)—offering an effective solution to the practical challenges of VUV NLO materials. The team’s findings were recently published in Nature.

The team’s key achievement is the development of centimeter-scale, high-quality ABF crystal growth and advanced anisotropic crystal processing technologies. Notably, ABF uniquely integrates a set of conflicting yet critical properties required for VUV NLO materials—excellent VUV transparency, a strong NLO coefficient, and substantial birefringence for VUV phase-matching—while fulfilling stringent practical criteria: large crystal size for fabricating devices with specific phase-matching angles, stable physical/chemical properties, a high laser-induced damage threshold, and suitable processability. This breakthrough resolves the long-standing field challenge where no prior crystal has met all these criteria simultaneously.

Ultrathin kagome metal hosts robust 3D flat electronic band state

A team of researchers at Monash University has uncovered a powerful new way to engineer exotic quantum states, revealing a robust and tunable three-dimensional flat electronic band in an ultrathin kagome metal, an achievement long thought to be nearly impossible. The study, “3D Flat Band in Ultra-Thin Kagome Metal Mn₃Sn Film,” by M. Zhao, J. Blyth, T. Yu and collaborators appears in Advanced Materials.

The discovery centers on Mn₃Sn films just three nanometers thick. Despite their extreme thinness, these films host a 3D flat band that spans the entire momentum space, offering an unprecedented platform for exploring strongly correlated quantum phases and designing future low-energy electronic technologies.

“Until now, 3D flat bands had only been observed in a few bulk materials with special lattice geometries,” said Ph.D. candidate and co-lead author James Blyth, from the Monash University School of Physics and Astronomy.

Thinking on different wavelengths: New approach to circuit design introduces next-level quantum computing

Quantum computing represents a potential breakthrough technology that could far surpass the technical limitations of modern-day computing systems for some tasks. However, putting together practical, large-scale quantum computers remains challenging, particularly because of the complex and delicate techniques involved.

In some quantum computing systems, single ions (charged atoms such as strontium) are trapped and exposed to electromagnetic fields including laser light to produce certain effects, used to perform calculations. Such circuits require many different wavelengths of light to be introduced into different positions of the device, meaning that numerous laser beams have to be properly arranged and delivered to the designated area. In these cases, the practical limitations of delivering many different beams of light around within a limited space become a difficulty.

To address this, researchers from The University of Osaka investigated unique ways to deliver light in a limited space. Their work revealed a power-efficient nanophotonic circuit with optical fibers attached to waveguides to deliver six different laser beams to their destinations. The findings have been published in APL Quantum.

New approach to circuit design introduces next-level quantum computing

Quantum computing represents a potential breakthrough technology that could far surpass the technical limitations of modern-day computing systems for some tasks. However, putting together practical, large-scale quantum computers remains challenging, particularly because of the complex and delicate techniques involved.

An example configuration of the proposed laser delivery photonic circuit chip. (Image: Reproduced from DOI:10.1063/5.0300216, CC BY)

Physicists built a perfect conductor from ultracold atoms

Scientists have built a quantum “wire” where atoms collide endlessly—but energy and motion never slow down. Researchers at TU Wien have discovered a quantum system where energy and mass move with perfect efficiency. In an ultracold gas of atoms confined to a single line, countless collisions occur—but nothing slows down. Instead of diffusing like heat in metal, motion travels cleanly and undiminished, much like a Newton’s cradle. The finding reveals a striking form of transport that breaks the usual rules of resistance.

In everyday physics, transport describes how things move from one place to another. Electric charge flows through wires, heat spreads through metal, and water travels through pipes. In each case, scientists can measure how easily charge, energy, or mass moves through a material. Under normal conditions, that movement is slowed by friction and collisions, creating resistance that weakens or eventually stops the flow.

Researchers at TU Wien have now demonstrated a rare exception. In a carefully designed experiment, they observed a physical system in which transport does not degrade at all.

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