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Category: quantum physics

Electrons in moiré crystals explore higher-dimensional quantum worlds

The electrons that power our society flow left and right through the circuitry in our electronics, back and forth along the transmission lines that make up our power grid, and up and down to light up every floor of every building. But the electrons in newly discovered “moiré crystals” move in much stranger ways. They can move left and right, back and forth, or up and down in our three-dimensional world, but these electrons also act as if they can teleport in and out of a mysterious fourth dimension of space that is perpendicular to our perceivable reality. Physicists have found that this strange, newly discovered quantum behavior has nothing to do with the electrons themselves and everything to do with the strange material environment in which they live.

The electrons in moiré crystals leap into a fourth dimension through a process called “quantum tunneling.” While a soccer ball sitting at the bottom of a hill will stay put until someone retrieves it, a quantum particle in a valley can jump out all on its own. Quantum tunneling may seem magical to us, but it is quite commonplace in the microscopic quantum world, on the length scales of atoms. Quantum tunneling is also important on larger length scales, particularly in large superconducting circuits that underlie an emerging landscape of quantum technology, as recognized by the 2025 Nobel Prize in Physics.

However, quantum tunneling in moiré crystals is different, in that once an electron tunnels, physicists have now measured that it acts as if it had tunneled into a completely different world and come back again, as if it had been transported through a fourth “synthetic” dimension.

A 200-year-old light trick just transformed quantum encryption

Scientists have unveiled a new approach to ultra-secure communication that could make quantum encryption simpler and more efficient than ever before. By harnessing a 19th-century optics phenomenon called the Talbot effect, researchers developed a system that sends information using multiple states of single photons instead of just two, dramatically boosting data capacity. Even more impressive, the setup works with standard components and requires only a single detector, reducing cost and complexity.

Microscopic mechanism of ‘quantum collapse’ in real-world environments uncovered for the first time

A research team has, for the first time in the world, elucidated the microscopic mechanism by which quantum order is lost and collapses in “open quantum environments” existing in nature. Since perfectly isolated quantum systems cannot exist in reality, this study is expected to provide a decisive breakthrough in bridging the gap between ideal quantum theory and quantum technologies that must operate in real-world environments.

The study is published in the journal Advanced Science. The study was led by Professor JaeDong Lee of the Department of Physics and Chemistry at DGIST.

How noise limits today’s quantum circuits

Imagine you’re trying to build a very long, complicated chain of dominoes. The aim is that each domino hits the next one perfectly, all the way down the line, producing an amazing result at the end. A quantum circuit is like a domino chain: a long chain of tiny steps (“operations”) that work together to process information together in a powerful way.

Now imagine that every domino is a little wobbly. In the quantum circuit, that wobble is called “noise.” It might not look like much—after all, all regular systems are subjected to some kind of “noise”—but noise in quantum circuits can accumulate and build up to a crescendo of problems.

Gravity from positivity: Single massive spin-3/2 particle makes gravity logically inevitable, study claims

Researchers at IPhT (CEA, CNRS) and the Universitat Autònoma de Barcelona have shown that gravity—and with it, supersymmetry—emerge as logical necessities whenever a massive spin-3/2 particle exists in nature. Two principles are enough: causality, the fact that no signal can travel faster than light, and unitarity, the requirement that probabilities are conserved in quantum mechanics. The structure of supergravity is not assumed: it bootstraps itself.

In fundamental physics, gravity is usually thought of as an ingredient one adds to a theory. But could it instead be forced by the internal consistency of the quantum world? This is what a study published in the Journal of High Energy Physics demonstrates.

The starting point is disarmingly simple: a single massive spin-3/2 particle. The authors show that such a particle simply cannot exist in isolation within a consistent theory. Its scattering amplitudes grow too fast with energy, clashing with positivity inequalities—the mathematical encoding of causality (the speed of light as an absolute limit) and unitarity (the conservation of probabilities in every quantum process). The theory breaks down barely above the particle’s own mass.

Novel approach to quantum error correction portends a scalable future for quantum computing

A University of Sydney quantum physicist has developed a new approach to quantum error correction that could significantly reduce the number of physical qubits required to build large-scale, fault-tolerant quantum computers. The study, co-authored by Dr. Dominic Williamson from the School of Physics, is titled “Low-overhead fault-tolerant quantum computation by gauging logical operators” and published in Nature Physics.

The work was done while Dr. Williamson was on a sabbatical working at global technology firm IBM in California. Elements of the new design have been integrated into IBM’s plan to build large-scale quantum computing.

“We’re at a point where theory and experiment are beginning to align,” Dr. Williamson said. “The big question now is how to design quantum computers that can be scaled efficiently to solve useful problems. Our work provides a promising blueprint.”

Quantum coherence could be preserved at large scales in realistic environments

Quantum states are notoriously fragile, and can be destroyed simply through interactions, measurements, and exposure to their surrounding environments. In a new theoretical study published in Physical Review X, Rohan Mittal and colleagues at the University of Cologne have discovered a new way to protect quantum behavior on large scales within systems driven far from equilibrium. Their results could have promising implications for the design of more robust quantum devices.

When quantum many-body systems are driven out of equilibrium, they undergo decoherence, causing quantum correlations and superpositions to break down. Even when such a system is built from entirely quantum components, the effect can cause its behavior to become indistinguishable from that of a classical system on larger scales, making it unsuitable for technologies such as quantum computing or sensing.

So far, researchers have attempted to solve the decoherence problem by fine-tuning two independent parameters: one to push the system to the boundary between two distinct quantum phases, and another to ensure that quantum coherence is maintained at this boundary. In practice, however, the need to account for two parameters simultaneously has made this approach both fragile and experimentally daunting.

The secrets of black holes and the Higgs mass could be hidden in a 7-dimensional geometry

One of the greatest mysteries of modern physics, the “black hole information paradox,” might have finally found an elegant solution, and the answer could also reveal the origins of the mass of fundamental particles.

In the 1970s, Stephen Hawking demonstrated, through semi-classical calculations, that black holes are not truly black, but emit a weak radiation that causes them to gradually shrink until they disappear.

This process, however, brings with it a massive problem: it seems to cause an irreversible loss of information, violating the unitarity principle of quantum mechanics. In other words, the laws of quantum physics state that information cannot be destroyed, but the evaporation of a black hole suggests otherwise.

A tiny detector for microwave photons could advance quantum tech

Detecting a single particle of light is hard; detecting a single microwave photon is even harder. Microwave photons, the tiny packets of electromagnetic radiation used in current technologies like Wi-Fi and radar, carry far less energy than visible light. They are about 100,000 times weaker than optical photons.

Many existing quantum technologies depend on detecting individual photons with high reliability. For visible light, this is well established using devices that convert incoming light directly into electrical signals. But at microwave frequencies (0.3–30 GHz), this fails because each individual photon doesn’t carry enough energy to release an electric charge into a material. This means that detecting single microwave photons requires a completely different strategy.

A long-standing goal has been to realize a simple device capable of continuously detecting microwave photons. Now, scientists at EPFL, led by Pasquale Scarlino, have developed a semiconductor-based detector that takes an important step in that direction.

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