Quantum tech breakthrough: China’s double-photon device breaks efficiency ceiling

Chinese scientists have cracked a long-standing puzzle in quantum optics, creating a tiny device that spits out pairs of light particles on demand with unprecedented purity and efficiency that could upend the quantum race.

Single-photon devices are maturing rapidly, but the field is now pursuing efficient two-photon sources that can pave the way for sharper medical imaging, unbreakable encryption and next-generation sensors. In precision measurement, for instance, using two photons can double the spatial resolution compared with a single photon.

The challenge with traditional quantum dots – tiny structures often called “artificial atoms” – is that getting them to emit just two photons at a time is like trying to balance two marbles on a needle. Now, a team of researchers from Beijing has found an innovative way that delivers exceptionally strong two-photon efficiency.

Under pulsed excitation conditions – the process of applying a brief, intense force or impulse to a structure – their new emitter can achieve 98.3 per cent of emitted photons appearing in paired form, with a generation efficiency of 29.9 per cent. Such results represent the current “international best-in-class” of its kind, according to its lead researcher.

The breakthrough, unveiled this week in Nature Materials, comes from a team at the Beijing Academy of Quantum Information Sciences led by chief scientist Yuan Zhiliang, in collaboration with researchers from the Chinese Academy of Sciences’ Institute of Semiconductors.

Ding Fei, a scientist from Leibniz University in Germany, wrote in a research briefing in the same journal that he was “truly impressed by the result shown here”.

South China Morning Post