Decoherence-Free Qubit and Chiral Emission from a Giant Molecule in Waveguide QED

TL;DR

This paper demonstrates a giant molecule in waveguide QED that combines decoherence-free qubits with highly directional chiral photon emission, enabling robust quantum information processing.

Contribution

It introduces a giant molecule architecture that achieves both decoherence protection and chiral emission within a single waveguide QED device.

Findings

Achieves 100% directionality in chiral photon emission.

Low measurement error of 1.2% in qubit readout.

Realizes universal single-qubit gates via atomic frequency modulation.

Abstract

Combining decoherence protection with directional photon emission in a single waveguide quantum electrodynamics (QED) device remains an open challenge. Here we show that an artificial giant molecule -- strongly interacting artificial atoms coupled to a photonic waveguide at multiple spatially separated points -- achieves both: a fully operational decoherence-free (DF) qubit and state-dependent chiral single-photon emission, arising from the same photon-interference mechanism. Initialization reduces to a local excitation of a single atom, universal single-qubit gates are implemented by modulating a single atomic frequency, and readout exploits state-dependent chiral emission with directionality reaching 100% and low measurement error of 1.2%. The coexistence of decoherence protection and directional emission in a single device positions giant molecules as protected chiral nodes for modular quantum networks in waveguide QED.