Optical spin tomography in a telecom C-band quantum dot

TL;DR

This paper demonstrates optical spin tomography of a telecom-band quantum dot, identifying the hole as a promising qubit for quantum networks and providing detailed diagnostics for entanglement applications.

Contribution

It introduces a method for benchmarking spin properties of telecom quantum dots and reveals the hole as the optimal qubit for spin-photon entanglement.

Findings

Hole identified as preferable qubit for entanglement

Full state tomography reveals spin anisotropies

Benchmarking of g-factors and coherence properties

Abstract

A central challenge for scalable quantum networks is the realization of coherent interfaces between stationary qubits and telecom-band photonic qubits for long-distance entanglement distribution. Semiconductor quantum dots emitting at telecom wavelengths present a promising spin-photon platform, and a precise understanding of the properties of the confined spin is crucial for optimizing its interplay with the photonic qubit. Here, we simultaneously benchmark the electron and hole g-factors and coherence properties of a droplet epitaxy QD, solely from time and polarization resolved photon correlations. These measurements identify the hole as the preferable qubit for spin-photon entanglement in quantum network nodes. We then perform full state tomography of the confined hole ground state to reveal subtle anisotropies in the spin precession, providing essential diagnostics for minimizing phase errors critical for deterministic multiphoton entanglement generation.