Dynamical blockade in a bosonic Josephson junction using optimal coupling

TL;DR

This paper demonstrates how optimal time-dependent Josephson coupling can enhance unconventional photon blockade in a two-mode bosonic system, leading to improved single-photon emission efficiency and easier detection.

Contribution

It introduces a numerical optimal control method to find time-dependent coupling that improves photon blockade and emission properties in coupled nonlinear bosonic modes.

Findings

Lower two-photon occupation achieved with optimal coupling.

Higher one-photon populations and longer emission windows.

Enhanced single-photon emission statistics compared to constant coupling.

Abstract

In this article we use time-dependent Josephson coupling to enhance unconventional photon blockade in a system of two coupled nonlinear bosonic modes which are initially loaded with weakly populated coherent states, so the evolution is restricted to the manifold of up to two field quanta. Using numerical optimal control, we find the optimal coupling which minimizes the two-photon occupation of one mode, which is actually transferred to the other, while maintains a non-zero one-photon occupation in the same mode. Moreover, we choose the continuous coupling to vanish after the transfer between the modes such that they are decoupled and one of them is left only with some one-photon population which can be observed upon its decay. We numerically find lower values of the second-order correlation function obtained at earlier times than with constant coupling, with larger one-photon populations and for longer time windows, corresponding thus to higher emission efficiency and easier detection. The presented methodology is not restricted to the system under study, but it can also be transferred to other related frameworks, to find the optimal driving fields which can improve the single-photon emission statistics from these systems.