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Category: quantum physics

Canceling Quantum Noise

A new technique uses an ‘anti-noise’ signal to cancel out the unavoidable quantum noise associated with precision measurements like those needed for gravitational-wave detection.

When light is used to detect motion with high-precision—for example, in accelerometers or gravitational-wave detectors—its ultimate sensitivity is limited by quantum noise, which is unavoidable. A research team has now demonstrated a tabletop device that can reduce the disruption of quantum noise by modifying a light beam before using it to make a measurement [1]. This beam preparation cancels out the noise in a manner reminiscent of noise-canceling headphones [1]. Working across a wide frequency range and potentially offering up to 77% noise reduction, the system might ultimately find additional uses in quantum information processing.

Observing gravitational waves involves detecting changes in the interference pattern created by a pair of interacting laser beams, each of which has bounced off a remote mirror whose distance changes slightly when a wave passes. Such detections require very high sensitivity, which is compromised by inherent quantum fluctuations in the light field. To reduce quantum noise, researchers currently use a technique called squeezing, in which the quantum fluctuations can be shifted from one parameter, such as the phase, to another, such as the intensity [2, 3].

Superconducting vortices moonlight as controllable qubits, turning a disruption into a resource

Vortices in superconductors have so far been considered a disruption, as they can impair the superconducting properties. Researchers at the Karlsruhe Institute of Technology (KIT) have proved in experiments that magnetic vortices can be used as controllable quantum systems in certain materials. This means that a previously unwanted phenomenon is becoming a potential resource in quantum technologies, opening up new avenues for the development of quantum computers, highly sensitive sensor systems, and innovative approaches in materials research. These results are published in Nature.

Superconductors are materials that, under certain conditions, conduct electricity with zero resistance, entirely expelling magnetic fields. However, once the magnetic flux exceeds a critical threshold, magnetic fields start to penetrate into the material as tiny, quantized vortices. Such vortices have so far been considered unwanted disruptive factors, as they have an energy-draining effect, limiting the efficiency of superconducting systems.

Why the intrinsic quantum effects of axion dark matter are completely undetectable

Dark matter is an elusive form of matter that almost never emits, absorbs or reflects light, while only weakly interacting with regular matter. These properties make it very difficult to detect using conventional experimental techniques and instruments.

Over the past decades, physicists have inferred the existence of dark matter indirectly, by probing its influence on the gravity of stars, galaxies and other cosmological objects. As it has never been directly observed before, the exact composition and nature of dark matter remain unknown.

A hypothetical dark matter particle is the axion, an ultralight particle that is predicted to be highly abundant in the universe. Most existing work describes axions as a classical field, a wave-like entity that resembles an electromagnetic field.

‘Designer’ superconducting diamond: Researchers uncover path to multi-modality quantum chips

Diamond is extremely valuable to science and technology not for its sparkle but for its extreme hardness, high thermal conductivity, transparency to a large fraction of the light spectrum, and a host of other exceptional properties. Two decades ago, scientists discovered another advantage: under the right conditions, diamond can become a superconductor—allowing electricity to flow through it with zero resistance.

Until recently, though, they knew little about how that happens, limiting its use in high-tech applications.

Now researchers from the Pennsylvania State University, the University of Chicago Pritzker School of Molecular Engineering (PME), and the U.S. Department of Energy National Quantum Information Science Research Center Q-NEXT, led by Argonne National Laboratory, have uncovered new insights into the physics behind the phenomenon by carefully creating high-quality diamond, isolating electronic signatures from material noise, and revealing the fundamental mechanisms that had long remained hidden.

Scientists just captured a mysterious quantum “dance” inside superconductors

Scientists just spotted a mysterious quantum “dance” that could rewrite superconductivity—and reshape future tech. For the first time, researchers have directly visualized the quantum behavior that drives superconductivity, a state in which paired electrons allow electricity to flow with zero resistance at very low temperatures.

But what they observed came as a surprise.

In a study published April 15 in Physical Review Letters, the team captured images of individual atoms forming pairs inside a specially prepared gas cooled to nearly absolute zero — the unreachable limit to how cold anything can get. This system, known as a Fermi gas, lets scientists replace electrons with atoms so they can study superconductivity in a highly controlled environment.

Black holes may avoid singularities when charge and Hawking radiation combine, theoretical physicist argues

Black holes are regions in space where gravity is so strong that nothing, even light, can escape. Einstein’s theory of general relativity breaks down inside black holes, either by the presence of a so-called “curvature singularity” or “Cauchy horizon.”

A curvature singularity is a point where density and spacetime curvature become infinite, the laws of physics break down, and matter is crushed into an infinitely small space. A Cauchy horizon, on the other hand, is a boundary beyond which the future cannot be reliably predicted by known physics theories.

Francesco Di Filippo, a researcher at the Institute for Theoretical Physics in Frankfurt, recently carried out a theoretical study that challenges the assumption that black holes must inevitability possess either a singularity or a Cauchy horizon. His paper, published in Physical Review Letters, shows that the combination of electromagnetic repulsion from electric charge and quantum effects described by Stephen Hawking’s radiation theory could prevent the formation of singularities and Cauchy horizons in some black holes.

Quantum supremacy just ran into an unexpected rival: An ordinary laptop armed with new math

Using a conventional computer and cutting-edge mathematical tools and code, physicists at the Center for Computational Quantum Physics (CCQ) at the Simons Foundation’s Flatiron Institute and collaborators at Boston University have cracked a daunting quantum physics problem previously claimed to be solvable only by quantum computers.

The technique is so groundbreaking in its efficiency that the researchers were even able to use a personal laptop to solve the problem.

By enabling scientists to squeeze extra problem-solving power from classical computers, the breakthrough methodology is opening new avenues for research on quantum dynamics and may be useful as a protocol for solving problems about finding the optimal solution amid an abundance of feasible ones.

Molecule-in-a-crystal system could boost quantum computing via chemically engineered qubits

Within a crystal’s atomic structure, tiny atomic-scale flaws will naturally occur where electrons can become trapped. These defects have emerged as one of the leading platforms for quantum information processing. Through a new study, posted to the preprint server arXiv, Ilai Schwartz and colleagues at NVision Imaging Technologies in Germany have shown that a specialized molecule embedded inside a crystal could take this approach a step further, offering a more controllable and versatile route to building quantum systems.

Unlike the classical computers we use every day, quantum computers encode information in the quantum states of qubits, which can exist in combinations of 0 and 1 simultaneously. This quantum information can’t simply be copied or transmitted in the same way as classical bits: when a qubit is measured, its quantum state is disturbed, making it impossible to transmit its information directly.

To tackle this problem, qubits must be connected to photons, which can transmit their quantum information between distant parts of a network. This connection relies on what physicists call a “spin-photon interface”: a structure in which the quantum state of an electron or nucleus can be reliably written, read, and communicated via light.

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