A new study reveals that spontaneous emission, a key phenomenon in the interaction between light and atoms, manifests in a new form within a photonic time crystal. This research, led by a KAIST team, not only overturns existing theory but further predicts a novel phenomenon: spontaneous emission excitation. The findings are published in the journal Physical Review Letters.

Professor Bumki Min’s research team from the KAIST Department of Physics, in collaboration with Professor Jonghwa Shin of the Department of Materials Science and Engineering, Professor Wonju Jeon of the Department of Mechanical Engineering, Professor Gil Young Cho of the Department of Physics, and researchers from IBS, UC Berkeley, and the Hong Kong University of Science and Technology, announced that they have proven that the spontaneous emission decay rate in a photonic time crystal is, on the contrary, enhanced rather than being “extinguished,” as suggested by a paper published in Science in 2022. Furthermore, they predicted a new process—spontaneous emission excitation—where an atom transitions from its ground state to an excited state while simultaneously emitting a photon.

Spontaneous emission is the process by which an atom intrinsically emits a photon and is fundamental to quantum optics and photonic device research. Until now, control over spontaneous emission has been achieved by designing spatial structures like resonators or photonic crystals. However, the advent of photonic time crystals, which periodically modulate the refractive index of a medium over time, has drawn attention to the potential for control along the time axis.

A new platform developed by Illinois Grainger engineers demonstrates the utility of a ytterbium-171 atom array in quantum networking. Their work represents a key step toward long-distance quantum communication.

Researchers from The Grainger College of Engineering at the University of Illinois Urbana-Champaign have introduced a scalable platform for quantum networking with a ytterbium-171 array.

Their work, published in Nature Physics, represents a major step toward larger quantum networks and has promising implications for modular quantum computation.

Bloch oscillations are periodic oscillations of quantum particles in a repeating energy “landscape” (e.g., a crystal lattice) that are subjected to a constant force. These particle motions have been the focus of numerous physics studies, as they are intriguing quantum effects that are not predicted by classical mechanics theories.

Probing Bloch oscillations experimentally could thus yield new insight into the fundamental properties of quantum matter. So far, they have been primarily studied in individual particles or two-particle systems, as opposed to quantum many-body systems comprised of several particles.

Researchers at CNRS-ENS-PSL University and Sorbonne University report the observation of collective Bloch oscillations in a one-dimensional (1D) Bose gas, a quantum fluid comprised of bosons, which are particles that can occupy the same quantum state.