Quantum optical interferometry via the mixing of coherent and photon-subtracted squeezed vacuum states of light

TLDR

Hofmann and Ono showed that mixing coherent light with single‑mode squeezed light at a beam splitter can approximate N00N states for phase‑shift measurements, and this proposal was experimentally realized by Afek et al. This paper aims to show that mixing coherent states with photon‑subtracted squeezed vacuum states at the first beam splitter of an interferometer improves phase‑shift measurement sensitivity using photon‑number detection. The approach mixes coherent states and photon‑subtracted squeezed vacuum states at the first beam splitter and measures photon numbers on one output beam. The authors demonstrate that N00N states of arbitrary photon number can be produced and that phase‑shift measurements are super‑resolved beyond what is achievable with coherent and squeezed vacuum light alone.

Abstract

Hofmann and Ono [Phys. Rev. A76, 031806, (2007)] showed that the mixing of coherent light and single-mode squeezed light at a beam splitter gives good approximation results in a superposition of path-entangled photon number states (so-called N00N states), which can be used for phase-shift measurements by coincident detections at the output of an interferometer. They showed that N00N states for arbitrary photon number N could be produced by this procedure. Afek et al. [Science328, 879 (2010)] have implemented the Hofmann–Ono proposal in the laboratory. In this paper, we show that, for a given coherent state amplitude and a given squeezing parameter, the mixing of coherent states and photon-subtracted squeezed vacuum states at the first beam splitter of an interferometer leads to improved phase-shift measurement sensitivity when using the photon-number detection technique on one of the output beams of the device. We also show that the phase-shift measurements will also be super-resolved to a greater degree than is possible by mixing coherent and squeezed vacuum light of the same field parameters.