High-fidelity quantum memory utilizing inhomogeneous nuclear polarization in a quantum dot

TL;DR

This paper demonstrates that inhomogeneous nuclear polarization in a quantum dot significantly enhances quantum memory performance by effectively utilizing strongly coupled nuclear spins, with narrower polarization distributions yielding better results.

Contribution

It introduces the concept that inhomogeneous nuclear polarization improves quantum memory in quantum dots, highlighting the importance of polarization distribution width.

Findings

Inhomogeneous nuclear polarization improves quantum memory performance.

Narrower polarization distributions lead to better memory fidelity.

Performance is linked to the entropy change of nuclear spins during encoding.

Abstract

We numerically investigate the encoding and retrieval processes for a quantum memory realized in a semiconductor quantum dot, by focusing on the effect of inhomogeneously polarized nuclear spins whose polarization depends on the local hyperfine coupling strength. We find that the performance of the quantum memory is significantly improved by the inhomogeneous nuclear polarization, as compared to the homogeneous one. Moreover, the narrower the nuclear polarization distribution is, the better the performance of the quantum memory is. We ascribe the performance improvement to the full harnessing of the highly polarized and strongly coupled nuclear spins, by carefully studying the entropy change of individual nuclear spins during encoding process. Our results shed new light on the implementation of a quantum memory in a quantum dot.