Lifeboat Foundation

The discovery that neutrinos have mass was groundbreaking. However, their absolute mass remains unknown. Neutrinoless double beta decay experiments aim to determine whether neutrinos are their own antiparticles and, if so, provide a means to determine the mass of the neutrino species involved.

Determining the mass through neutrinoless double beta decay experiments using ⁷⁶ Ge is only possible if scientists understand the properties of the decay of ⁷⁶ Ge into selenium-76 (⁷⁶ Se). A study published in Physical Review C provides key input for these kinds of experiments.

Germanium-based neutrinoless double beta decay (0νββ) experiments hold great promise for unraveling the mysteries surrounding neutrinos. The observation of this rare decay process not only offers the prospect of determining the nature of these enigmatic particles, but also the determination of their mass, provided the probability governing the decay is reliably known.

A team at HZB has developed a new measurement method that, for the first time, accurately detects tiny temperature differences in the range of 100 microKelvin in the thermal Hall effect. Previously, these temperature differences could not be measured quantitatively due to thermal noise.

Their study is published in Materials & Design.

Using the well-known terbium titanate as an example, the team demonstrated that the method delivers highly reliable results. The thermal Hall effect provides information about coherent multi-particle states in quantum materials based on their interaction with lattice vibrations (phonons).

Experiments with small falling particles show that their orientations oscillate—which may help explain the settling of volcanic ash and the formation of snow.

Ice crystals and volcanic ash fall through the atmosphere in a complicated way that has been hard to capture experimentally. A new lab experiment has photographed the descent of nonspherical plastic particles that were fabricated to resemble natural particles [1]. The images reveal oscillations in the particles’ orientations as they flitter downward. The results could help in modeling the formation of snow and the transparency of clouds, which is important for weather and climate models.

In order to study how micrometer-sized particles fall in the atmosphere, researchers must address the challenge of zooming in on the particles as they pass quickly in front of the camera. “The problem is that your field of view is so small that you have a very limited chance to see the particle for a long trajectory,” says Gholamhossein Bagheri from the Max Planck Institute for Dynamics and Self-Organization in Germany. Previously, researchers tried to solve this problem by performing experiments in water with easier-to-view centimeter-sized particles. The water slows the particle motion, but the ratio of particle size to fluid viscosity—which can be characterized by the dimensionless Reynolds number—remains roughly the same for larger, waterborne particles as for smaller, airborne particles. This correspondence between the two situations implies that water-based experiments can offer information about the speed and orientation of falling particles in the atmosphere.

Scientists have developed “quantum ping-pong”: Using a special lens, two atoms can be made to bounce a single photon back and forth with high precision.

Atoms can absorb and reemit light — this is an everyday phenomenon. In most cases, however, an atom emits a light particle in all possible directions — recapturing this photon is therefore quite hard.

Continue reading “Quantum Ping-Pong: The New Era of Atomic Photon Control” »

Researchers at Columbia University have successfully synthesized the first 2D heavy fermion material. They introduce the new material, a layered intermetallic crystal composed of cerium, silicon, and iodine (CeSiI), in a research article published in Nature.

Heavy fermion compounds are a class of materials with electrons that are up to 1,000 times heavier than usual. In these materials, electrons get tangled up with magnetic spins that slow them down and increase their effective mass. Such interactions are thought to play important roles in a number of enigmatic quantum phenomena, including superconductivity, the movement of electrical current with zero resistance.

Researchers have been exploring heavy fermions for decades, but in the form of bulky, 3D crystals. The new material synthesized by Ph.D. student Victoria Posey in the lab of Columbia chemist Xavier Roy will allow researchers to drop a dimension.

With modern electronic devices approaching the limits of Moore’s law and the ongoing challenge of power dissipation in integrated circuit design, there is a need to explore alternative technologies beyond traditional electronics. Spintronics represents one such approach that could solve these issues and offer the potential for realizing lower-power devices.

A collaboration between research groups led by Professor Barbaros Özyilmaz and Assistant Professor Ahmet Avsar, both affiliated with the Department of Physics and the Department of Materials Science and Engineering at the National University of Singapore (NUS), has achieved a significant breakthrough by discovering the highly anisotropic spin transport nature of two-dimensional black phosphorus.

The findings have been published in Nature Materials.

We study the competing effects of collective generalized measurements and interaction-induced scrambling in the dynamics of an ensemble of spin-1/2 particles at the level of quantum trajectories. This setup can be considered as analogous to the one leading to measurement-induced transitions in quantum circuits. We show that the interplay between collective unitary dynamics and measurements leads to three regimes of the average Quantum Fisher Information (QFI), which is a witness of multipartite entanglement, as a function of the monitoring strength. While both weak and strong measurements lead to extensive QFI density (i.e., individual quantum trajectories yield states displaying Heisenberg scaling), an intermediate regime of classical-like states emerges for all system sizes where the measurement effectively competes with the scrambling dynamics and precludes the development of quantum correlations, leading to sub-Heisenberg-limited states. We characterize these regimes and the crossovers between them using numerical and analytical tools, and discuss the connections between our findings, entanglement phases in monitored many-body systems, and the quantum-to-classical transition.

While interactions within a many-body quantum system tend to generate highly correlated states, performing local measurements will typically tend to disentangle the different subsystems. When combined, the interplay between these two effects often lead to measurement-induced transitions, which separate two distinct stable phases: one interaction-driven, where entanglement is high, and another measurement-driven, where entanglement is low. However, different types of measurements can lead to other scenarios, and often also generate entanglement themselves. In this work we study quantum many-body systems where both interactions and measurements take place collectively and thus generate a high degree of entanglement if acting separately. We show that nontrivial competition between these two actors emerges, leading to configurations with very low entanglement.

Research reveals the secrets of non-Heisenberg Tsai-type crystals that could open doors to applications in spintronics and magnetic refrigeration.

In 1960, Luttinger proposed a universal principle connecting the total capacity of a system for particles with its response to low-energy excitations. Although easily confirmed in systems with independent particles, this theorem remains applicable in correlated quantum systems characterized by intense inter-particle interactions.

However, and quite surprisingly, Luttinger’s theorem has been shown to fail in very specific and exotic instances of strongly correlated phases of matter. The failure of Luttinger’s theorem and its consequences on the behavior of quantum matter are at the core of intense research in condensed matter physics.