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Category: quantum physics

Quantum tunnelling

In physics, quantum tunnel ling, barrier penetration, or simply tunnel ling is a quantum mechanical phenomenon in which an object such as an electron or atom passes through a potential energy barrier that, according to classical mechanics, should not be passable due to the object not having sufficient energy to pass or surmount the barrier.

Tunnelling is a consequence of the wave nature of matter and quantum indeterminacy. The quantum wave function describes the states of a particle or other physical system and wave equations such as the Schrödinger equation describe their evolution. In a system with a short, narrow potential barrier, a small part of wavefunction can appear outside of the barrier representing a probability for tunnel ling through the barrier.

Since the probability of transmission of a wave packet through a barrier decreases exponentially with the barrier height, the barrier width, and the tunnel ling particle’s mass, tunnel ling is seen most prominently in low-mass particles such as electrons tunnel ling through atomically narrow barriers. However tunnel ling has been observed with protons and even atoms and tunnel ling has been used to explain physical effects with particles this large.

Quantum teleportation carries microwave states at temperatures up to 4 K, beating classical limit

A growing number of quantum engineers worldwide have been trying to realize large-scale quantum networks, which consist of several connected quantum computers or devices that share information with each other. The successful realization of these networks could potentially pave the way for the realization of new high-speed and secure communication systems, or even of a quantum version of the internet.

A key challenge when trying to realize large-scale quantum networks is ensuring that the quantum properties of microwave signals can be reliably transferred from one location to another. These signals are highly sensitive to random energy fluctuations associated with heat. Thus, systems introduced so far typically operate inside cooling machines known as dilution refrigerators.

Researchers at Walther-Meißner-Institute (WMI) and Technical University of Munich have introduced a new approach to successfully transfer quantum microwave states between two separate dilution refrigerators connected by a warmer superconducting cable, with temperatures of up to 4K.

Researchers push back fundamental limit on energy transfer between particles without ‘spilling’ radiation

Researchers at TU/e have demonstrated that energy transfer without loss via light or heat can occur over much greater distances than previously thought possible thanks to vibrations in microscopic gold rods. They succeeded in making energy jump from one particle to another over a distance of several millimeters without “spilling” energy along the way.

In the microscopic world in which this research takes place, that is a giant leap, with promising applications in quantum communication, solar energy, and ultrasensitive medical sensors. The researchers have published their findings in the journal Science Advances.

Normally, a molecule that absorbs energy loses it again as heat through vibrations passed on to the surrounding environment or as a particle of light (known as a photon). In Förster resonance energy transfer (or FRET for short, which is named after the German physicist Theodor Förster), something different happens: the energy jumps directly, without radiation, from one molecule to a specific neighboring molecule through an invisible interaction between their electric fields.

Perfect randomness realized for the first time

Creating perfect randomness is surprisingly difficult. Even modern random number generators never generate completely ideal random numbers: small systematic errors can result in some numbers appearing slightly more frequently than others. For many applications, this does not matter. In cryptography, however, even the tiniest deviations can be problematic.

Now, researchers at ETH Zurich led by Renato Renner and Andreas Wallraff in the Department of Physics have demonstrated how perfect randomness can actually be created using quantum physics. Their results, which have just been published in Nature, represent a milestone in this area of research.

Q&A: How researchers are building next-gen quantum computers

Quantum computers have the potential to transform science, accelerating breakthroughs in drug development, cosmology, materials science, nuclear physics, and more.

To make this future a reality, researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) are partnering with industry, academia, and the national labs to drive advances across the quantum computing “stack”—the hardware, software, and controls designed to ensure error-corrected quantum calculations.

“Making a functional quantum computer requires much more than qubits alone. It takes an entire technology stack that can harness quantum science for real-world applications,” said Chris Spitzer, operations lead at the Advanced Quantum Testbed (AQT).

The strange quantum property of tomorrow’s insulator

Ultra-fast data transfer and superconductivity: Quantum materials offer significant technological prospects—if we can understand them at the atomic scale. A team from the University of Geneva (UNIGE), in collaboration with the University of Salerno, the Institute of Materials Science of Barcelona, and the National Research Council of Italy, has succeeded in observing the “quantum metric” in a topological insulator—a unique geometric property of these materials, which conduct electricity only on their surface.

Published in Nature Materials, this work represents a major step toward mastering the materials of the future.

Not all materials conduct electricity in the same way. These differences arise from the behavior of the electrons that make up the material. Among them, topological insulators—discovered in 2006—are of particular interest to scientists. Like conventional insulators, they block the flow of electric current through their interior, yet, remarkably, allow it to flow freely across their surface.

Quantum computing may need far more than power as future data centers scale up

As quantum computing moves closer to large-scale deployment, new research is examining its future energy, water, and material demands.

David McCollum, an Oak Ridge National Laboratory distinguished scientist, is leading the project. McCollum is also a joint faculty professor in the Center for Energy, Transportation, and Environmental Policy (CETEP) at the Howard H. Baker Jr. School of Public Policy and Public Affairs at the University of Tennessee, Knoxville. The work aims to inform the rollout of quantum infrastructure over the coming decades. It examines technologies evolving from experimental environments to commercial-scale use. Quantum computing is expected to unlock advances in drug discovery, material science, artificial intelligence, and cybersecurity.

“Quantum computing presents extraordinary opportunities, from accelerating scientific discovery to solving complex optimization problems,” McCollum said. “At the same time, it introduces new questions about the energy, water, and materials required to operate these systems at scale. Our research aims to get ahead of those questions before resource and supply chain constraints start to bite.”

How dual-comb spectroscopy works and why it could reshape precision sensing

Spectroscopy has many applications, ranging from fundamental tests of quantum electrodynamics and investigations of molecular structure to environmental sensing, biomedical diagnostics and industrial monitoring. A highly promising spectroscopic instrument that has the potential to transform the field has emerged over the years: the dual-comb spectrometer, which relies on the interference of two mode-locked ultrafast lasers that produce broad frequency combs composed of evenly spaced narrow spectral lines.

A frequency comb is a spectrum of phase-coherent sharp laser lines that are evenly spaced. Such combs based on femtosecond mode-locked lasers, as pioneered at the Max-Planck Institute of Quantum Optics in the 1990s, have revolutionized measurements of frequency and time. In frequency metrology, a laser comb acts as a ruler in frequency space that conveniently links microwave and optical frequencies, and/or measures a large separation between two optical frequencies.

In the past two decades, frequency combs have found new applications. One of them is dual-comb spectroscopy. Dual-comb spectroscopy addresses the challenge of combining wide spectral coverage with high resolution and accuracy by using two optical frequency combs with slightly different repetition frequencies to map optical spectra directly into the radio-frequency domain. The method relies on time-domain interferometry and avoids mechanical scanning, enabling precise, rapid, and broadband measurements. Dual-comb spectroscopy has been implemented across the electromagnetic spectrum, from the terahertz to the visible range, with ongoing efforts towards the ultraviolet range.

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