Versatile engineering of multimode squeezed states by optimizing the pump spectral profile in spontaneous parametric down-conversion

TL;DR

This paper develops a theoretical framework and optimization method for engineering multimode squeezed states in spontaneous parametric down-conversion by tailoring the pump spectral profile, enhancing quantum correlations for quantum information applications.

Contribution

It introduces a novel theoretical approach and numerical optimization for pump spectral shaping to maximize squeezing and quantum correlations in SPDC processes.

Findings

Optimized pump profiles increase the number of squeezed modes.

Spectral shaping improves nullifier variances for cluster states.

Physical limitations of pulse shapers are considered in the optimization.

Abstract

We study the quantum correlations induced by spontaneous parametric down-conversion (SPDC) of a frequency comb. We derive a theoretical method to find the output state corresponding to a pump with an arbitrary spectral profile. After applying it to the relevant example of a spectrally chirped pump, we run an optimization algorithm to numerically find the pump profiles maximizing some target functions. These include the number of independently squeezed modes and the variances of nullifiers defining cluster states used in many continuous-variable quantum information protocols. To assess the advantages of pump-shaping in real experiments we take into account the physical limitations of the pulse shaper.