In recent years, there have been significant advances in the control and manipulation of fundamental quantum systems.  One of the growing interests in the field of quantum optics has been the realization of single photon subtraction, in which exactly one photon is always removed from an incoming laser beam.  Historically, such schemes are implemented in an inefficient and probabilistic manner, in which a successful subtraction is heralded by the detection of a subtracted photon, which is consequently lost.

Here we demonstrate a scheme for the deterministic extraction of a single photon from an incoming pulse [1].  Our implementation makes use of the single-photon Raman interaction (SPRINT) mechanism using a single atom coupled to a micro-resonator [2].  The removed photon is not detected, but rather extracted to a different mode.  This scheme can be applied on any three-level Λ-system in which each transition is coupled to a different direction of a single-mode waveguide with equal strength.

[1] Rosenblum, Serge, Orel Bechler, Itay Shomroni, Yulia Lovsky, Gabriel Guendelman, and Barak Dayan. "Extraction of a single photon from an optical pulse." arXiv preprint arXiv:1510.04042 (2015).

[2] Shomroni, Itay, Serge Rosenblum, Yulia Lovsky, Orel Bechler, Gabriel Guendelman, and Barak Dayan. "All-optical routing of single photons by a one-atom switch controlled by a single photon." Science 345, no. 6199 (2014): 903-906.