https://www.sciencedaily.com/releases/2022/06/220627125000.htm

"Just like an ordinary magnifying glass can zoom in on some spatial phenomena you wouldn't otherwise be able to see, a time lens lets you resolve details on a temporal scale," said Chaitali Joshi, the first author of the work and former PhD student in Alexander Gaeta's lab. A laser is a focused beam of many, many, many photons oscillating through space at a particular frequency; the team's time lens lets them pick out individual particles of light faster than ever before.

The experimental set-up consists of two laser beams that "mix" with a signal photon to create another packet of light at a different frequency. With their time lens, Joshi and her colleagues were able to identify single photons from a larger beam with picosecond resolution. That's 10-12 of a second and about 70x faster than has been observed with other single-photon detectors said Joshi, now a postdoc at CalTech. Such a time lens allows for temporally resolving individual photons with a precision that can't be achieved with current photon detectors.