Perfect quantum state transfer in a dispersion-engineered waveguide

• URL: http://arxiv.org/abs/2512.20212v1
• Date: Tue, 23 Dec 2025 10:05:53 GMT
• Title: Perfect quantum state transfer in a dispersion-engineered waveguide
• Authors: Zeyu Kuang, Oliver Diekmann, Lorenz Fischer, Stefan Rotter, Carlos Gonzalez-Ballestero,
• Abstract summary: High-fidelity state transfer is fundamentally limited by time-reversal symmetry.<n>We propose an alternative solution: by tailoring the dispersion relation of a waveguide, the photon pulse emitted by one qubit is passively reshaped into its time-reversed counterpart, thus enabling perfect absorption.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: High-fidelity state transfer is fundamentally limited by time-reversal symmetry: one qubit emits a photon with a certain temporal pulse shape, whereas a second qubit requires the time-reversed pulse shape to efficiently absorb this photon. This limit is often overcome by introducing active elements. Here, we propose an alternative solution: by tailoring the dispersion relation of a waveguide, the photon pulse emitted by one qubit is passively reshaped into its time-reversed counterpart, thus enabling perfect absorption. We analytically derive the optimal dispersion relations in the limit of small and large qubit-qubit separations, and numerically extend our results to arbitrary separations via multiparameter optimization. We further propose a spatially inhomogeneous waveguide that renders the state transfer robust to variations in qubit separations. In all cases, we obtain near-unity transfer fidelity (>= 98%). Our dispersion-engineered waveguide provides a compact and passive route toward on-chip quantum networks, highlighting engineered dispersion as a powerful resource in waveguide quantum electrodynamics.

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