Enabling Deterministic Passive Quantum State Transfer with Giant Atoms

TL;DR

This paper demonstrates how giant atoms coupled to 1D waveguides can enable passive, deterministic quantum state transfer with high fidelity, robustness, and no need for time-dependent control, advancing scalable quantum networks.

Contribution

It provides analytical conditions and optimization strategies for high-fidelity quantum state transfer using giant atoms, including in realistic finite-coupling configurations and dispersive environments.

Findings

Achieved up to 87% transfer fidelity with two coupling points.

Exceeded 99% fidelity with ten or more coupling points.

Showed robustness against disorder and dispersion effects.

Abstract

Achieving quantum state transfer in passive ways can become a powerful asset for scalable quantum networks. Here, we demonstrate how giant atoms coupled to 1D waveguides provide a platform for such a passive, deterministic transfer. Engineering the position and strength of coupling points, we show that the nonlocal interaction can be utilized for the emission of time-reversal-symmetric single-photon wavepackets by spontaneous decay. We first derive general analytical conditions under which arbitrary qubit decays can be mapped to wavevector-dependent couplings that guarantee perfect state transfer in the continuum limit of infinitely many coupling points. Then, for experimentally relevant configurations with a finite number of coupling points, we demonstrate that high transfer fidelities can still be achieved by optimization, reaching 87% with only two coupling points and exceeding 99% with ten or more. We further analyze the robustness of the protocol against disorder in leg positioning and extend the formalism to environments with nonlinear dispersion, showing that dispersion-induced distortions can be fully compensated by judiciously chosen setups. Our results establish giant atoms as a powerful platform for realizing high-fidelity quantum state transfer in a setting without time-dependent control, opening new avenues for scalable quantum networks and engineered light-matter interfaces.