Quantum Metrology with Two-Mode Squeezed Vacuum: Parity Detection Beats the Heisenberg Limit

We study the sensitivity and resolution of phase measurement in a Mach-Zehnder interferometer with two-mode squeezed vacuum ((n) over bar photons on average). We show that superresolution and sub-Heisenberg sensitivity is obtained with parity detection. In particular, in our setup, dependence of the signal on the phase evolves (n) over bar times faster than in traditional schemes, and uncertainty in the phase estimation is better than 1/(n) over bar, and we saturate the quantum Cramer-Rao bound.