A concept based on an exotic effect in periodic structures may be useful for developing future photonic devices.

A new way to marshal light within optical devices has been demonstrated experimentally by researchers in China. They have been able to induce light to organize itself into specific patterns of pulses as it circulates within a pair of optical fiber loops using a version of a phenomenon—called the non-Hermitian skin effect (NHSE)—that has been predicted but not observed previously [1]. The effect could be used to control light signals in photonic devices such as switches and routers.

In the standard theory for electron behavior in a metallic crystal, the periodic atomic structure leads to so-called Bloch waves—electron quantum states that spread across the entire crystal. But in recent years, theorists have found surprising results for a scenario in which one assumes that a particle such as an electron hops between neighboring sites in a periodic lattice asymmetrically—say, rightward hopping is more probable than leftward hopping. The particle’s quantum states become localized at the edge or surface of the lattice rather than spreading across it. This localization is the NHSE.

Embezzlement of entanglement is an exotic phenomenon in quantum information science, describing the possibility of extracting entanglement from a resource system without changing its quantum state. In this context, the resource systems play the role of a catalyst, enabling a state transition that would otherwise be impossible, without being consumed in the process. For embezzlement of entanglement to be possible, the resource state needs to be highly entangled.

The term “universal embezzler” refers to the idea of a bipartite quantum system where every state is sufficiently entangled to make embezzlement possible. So far, it seemed highly questionable that physical systems exhibiting such strong entanglement properties could exist in the first place.

Yet researchers at Leibniz University Hannover have now shown that universal embezzlement emerges in all critical fermion chains, meaning one-dimensional fermion systems at quantum phase transitions. While their paper, published in Nature Physics, is merely theoretical, it could open new possibilities for the study of many-body physics and for the development of quantum technologies.

Researchers at the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) have theoretically demonstrated that photons trapped inside an optical cavity carry detailed information about a material placed within it. By measuring the properties of the photons leaking out of the cavity, researchers can probe how an optical cavity modifies the properties of the embedded materials.

This insight opens new possibilities for experimental techniques to explore entangled light-matter systems. Their work has been published in Physical Review Letters.

According to basic quantum mechanics, empty space is not truly empty—it’s filled with particles that constantly pop in and out of existence, a phenomenon known as vacuum fluctuations. This process is somewhat analogous to atoms at the surface of boiling water, which continually jump in and out of the liquid.

Fermion chains have a hidden quantum ability that could reshape how we think about entanglement and information flow.