Squeezing in conditional measurement setup with coherent input

TL;DR

This paper demonstrates how to optimize squeezing in a conditional measurement setup using coherent and number states, with a focus on parameter tuning and accounting for experimental imperfections.

Contribution

It introduces a method to achieve maximal squeezing in a linear optical setup with coherent and number state inputs, using finite-dimensional state representation.

Findings

Maximal squeezing is achievable with fixed detection and optimized parameters.

Finite-dimensional representation simplifies squeezing calculation.

Experimental imperfections like impurity and inefficiency are considered.

Abstract

Conditional Measurement scheme which employs linear optical elements and photon detection is the fertile ground for nonclassical state generation. We consider a simple setup that requires a coherent state and a number state as inputs of the beam splitter, and a photon detector. We show that by tuning the parameters involved in the setup, we can achieve optimal squeezing from the setup. This is facilitated by writing the output state of the conditional measurement as displaced qudits. Setting aside displacement which plays no role in squeezing, the finite-dimensional representation makes it possible to calculate the maximal amount of squeezing. By fixing the detection at one photon level irrespective of any number state input and carefully chosen coherent parameter and beam splitter reflectivity values, one can reach the maximal squeezing at least for lower number state inputs. This is in contrast to the earlier attempts in atom field interaction models etc., where the squeezing obtained was far from saturation. To accommodate the experimental imperfections, we consider the impure nature of the photon source and detector inefficiency.