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Category: quantum physics – Page 14

Fano interference of photon pairs from a metasurface

Two-photon interference, a quantum phenomenon arising from the principle of indistinguishability, is a powerful tool for quantum state engineering and plays a fundamental role in various quantum technologies. These technologies demand robust and efficient sources of quantum light, as well as scalable, integrable, and multifunctional platforms. In this regard, quantum optical metasurfaces (QOMs) are emerging as promising platforms for the generation and engineering of quantum light, in particular pairs of entangled photons (biphotons) via spontaneous parametric down-conversion (SPDC). Due to the relaxation of the phase-matching condition, SPDC in QOMs allows different channels of biphoton generation, such as those supported by overlapping resonances, to occur simultaneously. In previously reported QOMs, however, SPDC was too weak to observe such effects.

Quantum networks bring new precision to dark matter searches

Detecting dark matter—the mysterious substance that holds galaxies together—is one of the greatest unsolved problems in physics. Although it cannot be seen or touched directly, scientists believe dark matter leaves weak signals that could be captured by highly sensitive quantum devices.

In a new study published in Physical Review D, researchers at Tohoku University propose a way to boost the sensitivity of quantum sensors by connecting them in carefully designed network structures. These quantum sensors use the rules of quantum physics to detect extremely small signals, making them far more sensitive than ordinary sensors. Using these, accurately detecting the faint clues left behind from dark matter could finally become possible.

The study focuses on , which are tiny electric circuits cooled to very low temperatures. These qubits are normally used as building blocks of quantum computers, but here they act as powerful quantum sensors. Just as a team working together can achieve more than a single person, linking many of these superconducting qubits in an optimized network allows them to detect weak dark matter signals much more effectively than any single sensor could on its own.

Quantum radio antenna uses Rydberg states for sensitive, all-optical signal detection

A team from the Faculty of Physics and the Center for Quantum Optical Technologies at the University of Warsaw has developed a new type of all-optical radio receiver based on the fundamental properties of Rydberg atoms. The new type of receiver is not only extremely sensitive, but also provides internal calibration, and the antenna itself is powered only by laser light.

The results of the work, in which Sebastian Borówka, Mateusz Mazelanik, Wojciech Wasilewski and Michał Parniak participated, were published in Nature Communications. They open a new chapter in the technological implementation of quantum sensors.

In today’s society, huge amounts of digital information are transmitted around us every second. Much of it is transmitted by radio, i.e. using . For a very long time, amplitude modulation has been used to encode information, sending stronger and weaker waves.

Old-school material could power quantum computing and cut data center energy use

A new twist on a classic material could advance quantum computing and make modern data centers more energy efficient, according to a team led by researchers at Penn State.

Barium titanate, first discovered in 1941, is known for its powerful electro-optic properties in bulk, or three-dimensional, crystals. Electro-optic materials like act as bridges between electricity and light, converting signals carried by electrons into signals carried by photons, or particles of light.

However, despite its promise, barium titanate never became the industry standard for electro-optic devices, such as modulators, switches and sensors. Instead, lithium niobate—which is more stable and easier to fabricate, even if its properties don’t quite measure up with those of barium titanate—filled that role instead. But by reshaping barium titanate into ultrathin strained thin films, this could change, according to Venkat Gopalan, Penn State professor of materials science and engineering and co-author of the study published in Advanced Materials.

Triplets born from proton collisions found to be correlated with each other

For the first time, by studying quantum correlations between triplets of secondary particles created during high-energy collisions in the LHC accelerator, it has been possible to observe their coherent production. This achievement confirms the validity of the core-halo model, currently used to describe one of the most important physical processes: hadronization, during which individual quarks combine to form the main components of matter in the universe.

Quarks and the gluons that bind them are the most numerous prisoners in today’s universe, locked inside protons, neutrons and mesons. However, at sufficiently high energies—such as those that existed shortly after the Big Bang or those that occur today in in the LHC accelerator—quarks and gluons are released, forming an exotic “soup”: . Under normal conditions, this plasma is not stable, and as soon as it cools down sufficiently, the quarks and gluons bind together again, producing in a process called hadronization.

New details of this fascinating phenomenon, obtained through the analysis of so-called three-body quantum correlations, have been reported by physicists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow, working as part of the LHCb experiment conducted by the European Organization for Nuclear Research (CERN) in Geneva.

G7 and Australia sign deal on quantum tech benchmarks

Scientists from the G7 nations and Australia signed an “unprecedented agreement” regarding quantum technology on Wednesday, France’s national metrology lab told AFP.

The deal between laboratories involved in the science of measurement hopes to establish benchmarks regarding progress in areas such as quantum computers.

The field has seen leading claim breakthroughs in recent years that have later been questioned by researchers.

Streamlined method to directly generate photons in optical fiber could secure future quantum internet

With the rise of quantum computers, the security of our existing communication systems is at risk. Quantum computers will be able to break many of the encryption methods used in current communication systems. To counter this, scientists are developing quantum communication systems, which utilize quantum mechanics to offer stronger security. A crucial building block of these systems is a single-photon source: a device that generates only one light particle at a time.

These photons, carrying quantum information, are then sent through optical fibers. For to work, it is essential that single photons are injected into optical fibers with extremely low loss.

In conventional systems, single-photon emitters, like and rare-earth (RE) element ions, are placed outside the fiber. These photons then must be guided to enter the fiber. However, not all photons make it into the fibers, causing high transmission loss. For practical quantum communication systems, it is necessary to achieve a high-coupling and channeling efficiency between the and the emitter.

Twice around to return home: A hidden reset button for spins and qubits

The world is filled with rotating objects—gyroscopes, magnetic spins, and more recently, qubits in quantum computers. For example, the atomic nuclei in our bodies precess at megahertz frequencies inside NMR machines. In practice, it is often desirable to return such a rotating system precisely to its starting point. At first glance, this seems impossible: after an elaborate sequence of twists and wobbles, how could one possibly retrace the path back to the origin?

The astonishing answer is that it is always possible. No matter how tangled the history of rotations, there exists a simple recipe: rescale the driving force and apply it twice. A single application is never sufficient, but applying this doubled, rescaled force guarantees an exact return. Under this operation, the spin—or the qubit, or any rotor—will unfailingly come home.

This discovery was made by Distinguished Professor Tsvi Tlusty from the Department of Physics at UNIST and Jean-Pierre Eckmann from the University of Geneva, Switzerland. Their study, published in Physical Review Letters on October 1, 2025, reveals that, despite their apparent complexity, rotations conceal a fundamental order.

Record spin waves thanks to flux quanta

Spin waves are considered to be promising candidates for a new form of electronics. Instead of electrons, the focus here is on magnons. These quantized units of spin waves describe how spin precession propagates. Similar to electrons, magnons can transmit information in a conductor. However, they do so with much lower resistance and thus a fraction of the energy consumption.

At TU Braunschweig, the Cryogenic Quantum Electronics working group, together with international partners, has now set a new record for the wavelength of excited propagating magnons. The researchers led by Professor Oleksandr Dobrovolskiy used another quasiparticle, fluxons, to excite the spin waves. The team collaborated with partners from Huazhong University of Science and Technology in China, Goethe University Frankfurt am Main, the University of Vienna and the University of Bordeaux.

“Fluxons move as magnetic flux quanta of a superconductor at speeds of up to 10 kilometers per second. We succeeded in using the ultra-fast fluxons to excite a spin wave in a neighboring magnet,” explains Dobrovolskiy. “This effect can be imagined as similar to the bow wave created by a speedboat in water. Except that our boat is so fast that it literally creates a kind of .”

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