Interfacing nuclear spins in quantum dots to cavity or traveling-wave fields

TL;DR

This paper proposes a method to connect optical fields with nuclear spins in quantum dots via a cavity, enabling quantum information transfer with high fidelity, even with current cavity lifetimes, by utilizing nuclear polarization and output field coupling.

Contribution

It introduces a novel scheme for quantum interfacing between optical fields and nuclear spins in quantum dots, tolerating shorter cavity lifetimes and leveraging nuclear polarization for high-fidelity quantum information transfer.

Findings

High-fidelity read-out and write-in of quantum information are feasible with current nuclear polarization levels.

The proposed scheme tolerates shorter cavity lifetimes than previous methods.

Nuclear polarization of ~90% enhances the performance of the quantum interface.

Abstract

We show how to realize a quantum interface between optical fields and the polarized nuclear spins in a singly charged quantum dot, which is strongly coupled to a high-finesse optical cavity. An effective direct coupling between cavity and nuclear spins is obtained by adiabatically eliminating the (far detuned) excitonic and electronic states. The requirements needed to map qubit and continuous variable states of cavity or traveling-wave fields to the collective nuclear spin are investigated: For cavity fields, we consider adiabatic passage processes to transfer the states. It is seen that a significant improvement in cavity lifetimes beyond present-day technology would be required for a quantum interface. We then turn to a scheme which couples the nuclei to the output field of the cavity and can tolerate significantly shorter cavity lifetimes. We show that the lifetimes reported in the literature and the recently achieved nuclear polarization of ~90% allow both high-fidelity read-out and write-in of quantum information between the nuclear spins and the output field. We discuss the performance of the scheme and provide a convenient description of the dipolar dynamics of the nuclei for highly polarized spins, demonstrating that this process does not affect the performance of our protocol.