An SU(1,1) interferometer replaces the beamsplitters in a Mach-Zehnder interferometer with nonlinear interactions and offers the potential of achieving high phase sensitivity in applications with low optical powers. We present a novel variation in which the second nonlinear interaction is replaced with balanced homodyne detection. The phase-sensing quantum state is a two-mode squeezed state produced by seeded four-wave-mixing in Rb vapor. Measurements as a function of operating point show that even with ≈35% loss this device can surpass the standard quantum limit by 4~dB.
@article{arxiv.1610.06891,
title = {Phase sensing beyond the standard quantum limit with a truncated SU(1,1) interferometer},
author = {Brian E. Anderson and Prasoon Gupta and Bonnie L. Schmittberger and Travis Horrom and Carla Hermann-Avigliano and Kevin M. Jones and Paul D. Lett},
journal= {arXiv preprint arXiv:1610.06891},
year = {2017}
}