Decoherence-free many-body Hamiltonians in nonlinear waveguide quantum electrodynamics

TL;DR

This paper introduces a new class of many-body Hamiltonians in nonlinear waveguide quantum electrodynamics that enable decoherence-free states and coherent control using global squeezing, advancing quantum technology applications.

Contribution

It demonstrates how nonlinear waveguides with parametric gain can produce robust many-body Hamiltonians that facilitate decoherence-free states without local emitter addressing.

Findings

Coupling strengths increase with emitter spacing in the proposed Hamiltonians.

Decoherence-free states can be generated from the ground state using global squeezing.

Dynamics approach a unitary evolution in the weak intra-waveguide squeezing limit.

Abstract

Enhancing interactions in many-body quantum systems, while protecting them from environmental decoherence, is at the heart of many quantum technologies. Waveguide quantum electrodynamics is a promising platform for achieving this, as it hosts infinite-range interactions and decoherence-free subspaces of quantum emitters. However, as coherent interactions between emitters are typically washed out in the wavelength-spacing regime hosting decoherence-free states, coherent control over the latter becomes limited, and many-body Hamiltonians in this important regime remain out of reach. Here we show that by incorporating emitter arrays with nonlinear waveguides hosting parametric gain, we obtain a unique class of many-body interaction Hamiltonians with coupling strengths that increase with emitter spacing, and persist even for wavelength-spaced arrays. We then propose to use these Hamiltonians to coherently generate decoherence-free states directly from the ground state, using only global squeezing drives, without the need for local addressing of individual emitters. Interestingly, we find that the dynamics approaches a unitary evolution in the limit of weak intra-waveguide squeezing, and discuss potential experimental realizations of this effect. Our results pave the way towards coherent control protocols in waveguide quantum electrodynamics, with applications including quantum computing, simulation, memory and nonclassical light generation.