Optimized Double-Well Quantum Interferometry with Gaussian Squeezed States
Y. P. Huang, M. G. Moore · Physical Review Letters · 2008
A Mach-Zender interferometer with a Gaussian number-difference squeezed input state can exhibit sub-shot-noise phase resolution over a large phase interval. We derive the optimal level of squeezing for a given phase interval $\ensuremath{\Delta}{\ensuremath{\theta}}_{0}$ and particle number $N$. We then propose an adaptive measurement sequence in which the amount of squeezing is increased with each measurement. With this scheme, any phase on $(\ensuremath{-}\ensuremath{\Delta}{\ensuremath{\theta}}_{0},\ensuremath{\Delta}{\ensuremath{\theta}}_{0})$ can be measured with a precision of $3.5/N$, requiring only 2--4 measurements, provided only that $N\mathrm{tan}(\ensuremath{\Delta}{\ensuremath{\theta}}_{0})<{10}^{40}$. In a double-well Bose-Einstein condensate, the optimized input states can be created by adiabatic manipulation of the ground state.