Photon-subtracted two-mode squeezed vacuum states and applications to quantum optical interferometry

We study the application of photon-subtracted two-mode squeezed vacuum states (TMSVS), where identical photon numbers are subtracted from each beam, to the problem of quantum optical interferometry with the photon-number parity measurements scheme. Previously, Anisimov et al. [Phys. Rev. Lett. 104, 103602 (2010)] have studied the prospect of using the TMSVS for parity measurements based interferometry. However, the joint photon number distribution of this state before beam splitting is thermal-like in each mode, meaning that its statistics are super-Poissonian and that the most probable state of the field is the double vacuum and that the average photon number is low. Furthermore, with these states the sensitivity of the phase-shift measurement is extremely sensitive to the size of the phase shift to be measured for large average photon numbers. The simultaneous subtraction of 1, 2, or 3 photons from each mode has the effects of increasing the average photon numbers of each mode and rendering the statistics nearly Poissonian and in some cases sub-Poissonian. We show that phase uncertainties for such states are less sensitive to the phase shift itself at large average photon numbers. We also show that the photon-subtracted TMSVS also lead to increased resolution. (c) 2012 Optical Society of America