Quantum nonreciprocity from qubits coupled by Dzyaloshinskii-Moriya interaction

TL;DR

This paper theoretically demonstrates how Dzyaloshinskii-Moriya interaction enables tunable quantum nonreciprocity, entanglement control, and photon correlation reshaping in waveguide QED systems, without chiral waveguides.

Contribution

It introduces a method to induce and control quantum nonreciprocity and entanglement using DMI in waveguide QED, expanding potential applications in quantum devices.

Findings

DMI enables strong, tunable nonreciprocity in waveguide QED.

Pure states lead to power-independent perfect transparency.

DMI reshapes photon statistics and shifts superbunching from transmission to reflection.

Abstract

We present a theoretical study of quantum nonreciprocity induced via a Dzyaloshinskii-Moriya interaction (DMI) in an otherwise achiral, waveguide quantum electrodynamics. Using the full quantum master equation and input-output formalism for two-level systems coupled to a one-dimensional waveguide and driven by a coherent field, we show that an engineered DMI enables strong nonreciprocity in an otherwise reciprocal system, with tunable behavior governed by driving strength, detunings, and phase of the DMI. Using it not only demonstrates nonreciprocal transmission but also demonstrates nonreciprocal quantum entanglement and photon bunching. The system can end up in a pure state as certain decohering channels do not participate. The pure state leads to power-independent perfect transparency. Conditions are derived and depend on the propagation phase, the relative detuning of the two qubits, and the exchange interaction. At these pure-state points, the steady-state entanglement is reciprocal and admits a closed-form expression; away from them, phase control generates strong entanglement nonreciprocity. The DMI also reshapes photon statistics, redistributing two-photon correlations and shifting superbunching from transmission (no DMI) to reflection at finite DMI. These results establish DMI as a versatile resource for engineering nonreciprocity, transparency, entanglement, and photon correlations in waveguide QED, enabling isolators, routers, and superbunching light sources without requiring chiral waveguides.