We propose and implement a quantum procedure for enhancing the sensitivity with which one can determine the phase shift experienced by a weak light beam possessing thermal statistics in passing through an interferometer. Our procedure entails subtracting exactly one (which can be generalized to m) photons from the light field exiting an interferometer containing a phase-shifting element in one of its arms. As a consequence of the process of photon subtraction, and somewhat surprisingly, the mean photon number and signal-to-noise ratio of the resulting light field are thereby increased, leading to enhanced interferometry. This method can be used to increase measurement sensitivity in a variety of practical applications, including that of forming the image of an object illuminated only by weak thermal light.
@article{arxiv.1605.05424,
title = {Interferometry with Photon-Subtracted Thermal Light},
author = {Seyed Mohammad Hashemi Rafsanjani and Mohammad Mirhosseini and Omar S. Magana-Loaiza and Bryan T. Gard and Richard Birrittella and B. E. Koltenbah and C. G. Parazzoli and Barbara A. Capron and Christopher C. Gerry and Jonathan P. Dowling and Robert W. Boyd},
journal= {arXiv preprint arXiv:1605.05424},
year = {2017}
}