Quantum Interferometry with Gaussian States
Ulrik L. Andersen, O. Glöckl, Tobias Gehring, Gerd Leuchs · 2016
The concept of quantum interference is at the very heart of quantum physics and appears in many areas. Most of the applications of interferometric light interference are concerned with the estimation of a linear phase shift between the two arms of a Mach-Zehnder interferometer, and to quantify the performance of the interferometer. One needs to address the precision by which this phase difference can be estimated. This chapter focuses on one simple setup with different combinations of Gaussian states at the input and using simple calculus to determine the interferometric precision. In real-life experiments, the concept of photon loss is important. The chapter deals with a short discussion of photon loss. For the Gaussian schemes mentioned, sub-shot-noise sensitivity is obtained for any nonvanishing squeezing even in the presence of photon loss. Finally, the chapter discusses quantum interferometry using non-Gaussian states.