# Photon pair condensation by engineered dissipation

## TL;DR

This paper demonstrates how engineered photon-pair dissipation can stabilize a unique quantum condensate with long-range pair correlations, using circuit-QED systems to realize such states.

## Contribution

It introduces a method to stabilize photon-pair condensates with phase-nematic order through engineered dissipation, including a scheme to select a specific parity sector.

## Key findings

- Stabilization of a photon pair condensate with long-range order
- Implementation scheme in circuit-QED architecture
- Control of parity sectors via Glauber dynamics

## Abstract

Dissipation can usually induce detrimental decoherence in a quantum system. However, engineered dissipation can be used to prepare and stabilize coherent quantum many-body states. Here, we show that by engineering dissipators containing photon pair operators, one can stabilize an exotic dark state, which is a condensate of photon pairs with a phase-nematic order. In this system, the usual superfluid order parameter, i.e. single-photon correlation, is absent, while the photon pair correlation exhibits long-range order. Although the dark state is not unique due to multiple parity sectors, we devise an additional type of dissipators to stabilize the dark state in a particular parity sector via a diffusive annihilation process which obeys Glauber dynamics in an Ising model. Furthermore, we propose an implementation of these photon-pair dissipators in circuit-QED architecture.