# Phase estimation with squeezed single photons. (arXiv:1802.02922v1 [quant-ph])

We address the performance of an interferometric setup in which a squeezed

single photon interferes at a beam splitter with a coherent state. Our analysis

in based on both the quantum Fisher information and the sensitivity when a

Mach-Zehnder setup is considered and the difference photocurrent is detected at

the output. We compare our results with those obtained feeding the

interferometer with a squeezed vacuum (with the same squeezing parameter of the

squeezed single photon) and a coherent state in order to have the same total

number of photons circulating in the interferometer. We find that for fixed

squeezing parameter and total number of photons there is a threshold of the

coherent amplitude interfering with the squeezed single photon above which the

squeezed single photons outperform the performance of squeezed vacuum (showing

the highest quantum Fisher information). When the difference photocurrent

measurement is considered, we can always find a threshold of the squeezing

parameter (given the total number of photons and the coherent amplitude) above

which squeezed single photons can be exploited to reach a better sensitivity

with respect to the use of squeezed vacuum states also in the presence of non

unit quantum efficiency.