Optimized parameter estimation in the presence of collective phase noise

Understand

We investigate phase and frequency estimation with different measurement strategies under the effect of collective phase noise.

• First, we consider the standard linear estimation scheme and present an experimentally realisable optimization of the initial probe states by collective rotations.
• We identify the optimal rotation angle for different measurement times.
• Second, we show that sub-shot noise sensitivity - up to the Heisenberg limit - can be reached in presence of collective phase noise by using differential interferometry, where one part of the system is used to monitor the noise.