Feedback-induced nonlinearity and superconducting on-chip quantum optics

TL;DR

This paper demonstrates how quantum feedback in superconducting circuits can induce strong nonlinear optical effects, such as bistability and photon anti-bunching, enabling advanced on-chip quantum dynamics engineering.

Contribution

It proves that superconducting circuit QED systems with coherent feedback can induce nonlinear phenomena in linear resonators, a novel approach for on-chip quantum optics.

Findings

Bistability can occur in superconducting resonators with feedback.

Photon anti-bunching is observable in the quantum regime.

Feedback enables control of nonlinear quantum dynamics.

Abstract

Quantum coherent feedback has been proven to be an efficient way to tune the dynamics of quantum optical systems and, recently, those of solid-state quantum circuits. Here, inspired by the recent progress of quantum feedback experiments, especially those in mesoscopic circuits, we prove that superconducting circuit QED systems, shunted with a coherent feedback loop, can change the dynamics of a superconducting transmission line resonator, i.e., a linear quantum cavity, and lead to strong on-chip nonlinear optical phenomena. We find that bistability can occur under the semiclassical approximation, and photon anti-bunching can be shown in the quantum regime. Our study presents new perspectives for engineering nonlinear quantum dynamics on a chip.