Protection of center-spin coherence by a dynamically polarized nuclear spin core

TL;DR

This paper demonstrates that a polarized nuclear spin core in a quantum dot can significantly protect the electron spin coherence, potentially enabling longer-lived qubits and quantum memories in solid-state systems.

Contribution

It reveals the formation of a polarized nuclear core that reduces electron spin relaxation, offering a new mechanism for enhancing qubit coherence in solid-state quantum systems.

Findings

Polarized nuclear core forms during dynamical polarization.

Protection effect reduces electron spin decay rate by a factor of N_1.

Applicable to quantum dots and defect centers like NV centers.

Abstract

Understanding fully the dynamics of coupled electron-nuclear spin systems, which are important for the development of long-lived qubits based on solid-state systems, remains a challenge. We show that in a singly charged semiconductor quantum dot with inhomogeneous hyperfine coupling, the nuclear spins relatively strongly coupled to the electron spin form a polarized core during the dynamical polarization process. The polarized core provides a protection effect against the electron spin relaxation, reducing the decay rate by a factor of $N_1$, the number of the nuclear spins in the polarized core, at a relatively small total polarization. This protection effect may occur in quantum dots and solid-state spin systems defect centers, such as NV centers in diamonds, and could be harnessed to fabricate in a relatively simple way long-lived qubits and quantum memories.