Efficient High-Fidelity Flying Qubit Shaping

TL;DR

This paper develops a comprehensive theory for efficient, high-fidelity conversion of matter qubits to flying photonic qubits, proposing new optimization strategies and protocols applicable across various quantum systems.

Contribution

It introduces a novel approach to optimize the temporal mode of emitted photons directly, enhancing fidelity and efficiency in matter-to-photon qubit conversion.

Findings

Derived upper bounds for emission efficiency of arbitrary matter qubit states.

Proposed a paradigm shift to optimize photon temporal modes instead of drive parameters.

Introduced protocols for time-bin encoding and spin-photon entanglement.

Abstract

Matter qubit to traveling photonic qubit conversion is the cornerstone of numerous quantum technologies such as distributed quantum computing, as well as several quantum internet and networking protocols. We formulate a theory for stimulated Raman emission which is applicable to a wide range of physical systems including quantum dots, solid state defects, and trapped ions, as well as various parameter regimes. We find the upper bound for the photonic pulse emission efficiency of arbitrary matter qubit states for imperfect emitters and show a path forward to optimizing the fidelity. Based on these results we propose a paradigm shift from optimizing the drive to directly optimizing the temporal mode of the flying qubit using a closed-form expression. Protocols for the production of time-bin encoding and spin-photon entanglement are proposed. Furthermore, the mathematical idea to use input-output theory for pulses to absorb the dominant emission process into the coherent dynamics, followed by a non-Hermitian Schr\"odinger equation approach has great potential for studying other physical systems.