A research team affiliated with UNIST has successfully demonstrated the experimental creation of collective quantum entanglement rooted in dark states—previously confined to theoretical models. The findings are published online in Nature Communications.

Unlike bright states, dark states are highly resistant to external disturbances and exhibit remarkably extended lifetimes, making them promising candidates for next-generation quantum technologies such as quantum memory and ultra-sensitive sensors.

Led by Professor Je-Hyung Kim in the Department of Physics at UNIST, in collaboration with Dr. Changhyoup Lee from the Korea Research Institute of Standards and Science (KRISS) and Dr. Jin Dong Song from the Korea Institute of Science and Technology (KIST), the team has achieved the controlled induction of dark state-based collective entanglement. Remarkably, this entanglement exhibits a lifetime approximately 600 times longer than that of conventional bright states.

Researchers at NPL have reported a novel high-speed charge sensing method for ballistic electrons, a potentially useful technique in the fields of electron quantum optics, quantum electrical metrology, flying qubit technology, and signal sensing.

The study, published in Physical Review Letters, reveals that the presence of a single ballistic electron can be revealed by tracking the path of another fast-moving “sensing” electron. By steering the paths of these electrons close to each other, the tiny repulsion between them can redirect the sensing electron, like a train switching tracks or cars diverting off a freeway.

When charge sensors are used in quantum devices, they are measured continuously, with each sample long enough to resolve a signal from the noise. The NPL sensing system leverages synchronization between the detector and sensing electrons to achieve extreme time selectivity, only sampling within a minuscule time window and detecting interactions that occur in just 1–2 picoseconds.