Stabilization of multi-mode Schrodinger cat states via normal-mode dissipation engineering

TL;DR

This paper demonstrates how to stabilize multi-mode Schrödinger cat states in nonlinear resonator arrays using engineered dissipation, enabling scalable quantum state preparation with enhanced noise bias for quantum information encoding.

Contribution

It extends dissipation engineering techniques to multi-mode systems, providing exact solutions and scalable state preparation methods for multi-mode Schrödinger cat states.

Findings

Exact steady-state solutions for multi-mode cat states.

Deterministic preparation of even parity multi-mode cat states.

Relaxation time is independent of system size, enabling scalability.

Abstract

Non-Gaussian quantum states have been deterministically prepared and autonomously stabilized in single- and two-mode circuit quantum electrodynamics architectures via engineered dissipation. However, it is currently unknown how to scale up this technique to multi-mode non-Gaussian systems. Here, we upgrade dissipation engineering to collective (normal) modes of nonlinear resonator arrays and show how to stabilize multi-mode Schrodinger cat states. These states are multi-photon and multi-mode quantum superpositions of coherent states in a single normal mode delocalized over an arbitrary number of cavities. We consider tailored dissipative coupling between resonators that are parametrically driven and feature an on-site nonlinearity, which is either a Kerr-type nonlinearity or an engineered two-photon loss. For both types of nonlinearity, we find the same exact closed-form solutions for the two-dimensional steady-state manifold spanned by superpositions of multi-mode Schrodinger cat states. We further show that, in the Zeno limit of strong dissipative coupling, the even parity multi-mode cat state can be deterministically prepared from the vacuum. Remarkably, engineered two-photon loss gives rise to a fast relaxation towards the steady state, protecting the state preparation against decoherence due to intrinsic single-photon losses and imperfections in tailored dissipative coupling, which sets in at longer times. The relaxation time is independent of system size making the state preparation scalable. Multi-mode cat states are naturally endowed with a noise bias that increases exponentially with system size and can thus be exploited for enhanced robust encoding of quantum information.