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Category: quantum physics – Page 7

At ultracold temperatures, interatomic collisions are relatively simple, and their outcome can be controlled using a magnetic field. However, research by scientists led by Prof. Michal Tomza from the Faculty of Physics of the University of Warsaw and Prof. Roee Ozeri from the Weizmann Institute of Science shows that this is also possible at higher temperatures. The scientists published their observations in the journal Science Advances.

Near absolute zero, interatomic collisions show simple behavior, and researchers can control and alter their effects. As the temperature increases, so does the , which radically complicates the collision mechanism. As a result, controlling the collisions becomes difficult. At least that is what has been thought so far.

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Phase transitions, like water freezing into ice, are a familiar part of our world. But in quantum systems, they can behave even more dramatically, with quantum properties such as Heisenberg uncertainty playing a central role. Furthermore, spurious effects can cause the systems to lose, or dissipate, energy to the environment. When they happen, these “dissipative phase transitions” (DPTs) push quantum systems into new states.

There are different types or “orders” of DPTs. First-order DPTs are like flipping a switch, causing abrupt jumps between states. Second-order DPTs are smoother but still transformative, changing one of the system’s global features, known as symmetry, in subtle yet profound ways.

DPTs are key to understanding how quantum systems behave in non-equilibrium conditions, where arguments based on thermodynamics often fail to provide answers. Beyond pure curiosity, this has practical implications for building more robust quantum computers and sensors. For example, second-order DPTs could enhance quantum information storage, while first-order DPTs reveal important mechanisms of system stability and control.

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However, as with much of quantum physics, this “language”—the interaction between spins—is extraordinarily complex. While it can be described mathematically, solving the equations exactly is nearly impossible, even for relatively simple chains of just a few spins. Not exactly ideal conditions for turning theory into reality…

A model becomes reality

Researchers at Empa’s nanotech@surfaces laboratory have now developed a method that allows many spins to “talk” to each other in a controlled manner – and that also enables the researchers to “listen” to them, i.e. to understand their interactions. Together with scientists from the International Iberian Nanotechnology Laboratory and the Technical University of Dresden, they were able to precisely create an archetypal chain of electron spins and measure its properties in detail. Their results have now been published in the renowned journal Nature Nanotechnology.

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Ever since their discovery almost four decades ago, high-temperature superconductors have fascinated scientists and engineers alike. These materials, primarily cuprates, defy classical understanding because they conduct electricity without resistance at temperatures far higher than traditional superconductors. Yet despite decades of research, we still don’t have a clear, comprehensive microscopic picture of how superconductivity emerges in these complex materials.

During my Ph.D. at Caltech, I was intrigued by the profound puzzle presented by high-temperature superconductors: Can we directly compute their from fundamental quantum mechanics without relying on simplified models or approximations? With this question, I embarked on a challenging but rewarding scientific journey.

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Researchers from Würzburg have experimentally demonstrated a quantum tornado for the first time by refining an established method. In the quantum semimetal tantalum arsenide (TaAs), electrons in momentum space behave like a swirling vortex. This quantum phenomenon was first predicted eight years ago by a Dresden-based founding member of the Cluster of Excellence ct.qmat.

The discovery, a collaborative effort between ct.qmat, the research network of the Universities of Würzburg and Dresden, and international partners, has now been published in Physical Review X.

Scientists have long known that electrons can form vortices in quantum materials. What’s new is the proof that these tiny particles create tornado-like structures in momentum space—a finding that has now been confirmed experimentally. This achievement was led by Dr. Maximilian Ünzelmann, a group leader at ct.qmat—Complexity and Topology in Quantum Matter—at the Universities of Würzburg and Dresden.

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Quantum information processing is a field that relies on the entanglement of multiple photons to process vast amounts of information. However, creating multiphoton entanglement is a challenging task. Traditional methods either use quantum nonlinear optical processes, which are inefficient for large numbers of photons, or linear beam-splitting and quantum interference, which require complex setups prone to issues like loss and crosstalk.

A team of researchers from Peking University, Southern University of Science and Technology, and the University of Science and Technology of China have made a significant breakthrough in this area.

As reported in Advanced Photonics Nexus, they developed a new approach using metasurfaces, which are planar structures capable of controlling various aspects of light, such as phase, frequency, and polarization. This innovative approach allows for the generation of multiphoton entanglement on a single , simplifying the process while making it more efficient.

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Physicists have proposed a radical approach that questions decades of belief about how gravity, spacetime, and quantum mechanics might fit together.

They have introduced a theory that keeps the classical concept of spacetime as envisioned by Einstein, even as it addresses a long-standing rift in modern physics.

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