Frontier Research Institute for Interdisciplinary Sciences
Tohoku University


High-efficiency single-photon generation via large-scale active time multiplexing


Assistant professor Fumihiro Kaneda at FRIS, Tohoku University and Professor Paul Kwiat at University of Illinois have built the world’s most efficient single-photon source.
A single photon, a smallest unit of light, is a proposed resource in quantum computation and communication, serving as a quantum bit, or qubit. To produce photons quantum optics researchers often used nonlinear-optics effect where one of billions of photons in a laser pulse is split into a pair of low-energy photons. However, this photon-pair production is probabilistic; it can produce nothing (typically with over 90% probability), one pair, or two pairs.
Kaneda and Kwiat solved this low-efficiency problem using a technique called time multiplexing. Their technique also uses a nonlinear-optics source but photons produced at random times are adaptively delayed via quantum memory so that produced photons are temporally multiplexed to enhance the presence probability of a single photon at the fixed time.  
They are still improving the multiplexed single-photon source. Their planned upgrades would enable to produce 30 to 50 single photons simultaneously at unprecedented efficiencies. Although this is much smaller than the number of bits handled in an ordinary computer, quantum computation with such a small number of qubits could be comparable or faster than a supercomputer for some types of computations.
The researchers’ current findings were published online in Science Advances on October 4, 2019.
Publication Detail:
F. Kaneda, P. G. Kwiat, "High-efficiency single-photon generation via large-scale active time multiplexing", Science Advances, Vol. 5, eaaw8586 (2019)
DOI: 10.1126/sciadv.aaw8586