Controlled tunneling induced dephasing of Rabi rotations for ultra-high fidelity hole spin initialization

TL;DR

This paper demonstrates sub-picosecond, high-fidelity hole spin initialization in quantum dots by controlling tunneling-induced dephasing, with implications for quantum information processing.

Contribution

It introduces a method to tailor tunneling timescales to achieve ultrafast, high-fidelity hole spin initialization without external magnetic fields.

Findings

Achieved >98.5% fidelity in spin initialization

Demonstrated tunneling induced dephasing as a tool for measuring tunneling times

Enabled ultrafast hole spin initialization with near-unity fidelity

Abstract

We report the sub-picosecond initialization of a single heavy hole spin in a self-assembled quantum dot with >98.5 % fidelity and without external magnetic field. Using an optically adressable charge and spin storage device we tailor the relative electron and hole tunneling escape timescales from the dot and simultaneously achieve high-fidelity initialization, long hole storage times and high efficiency readout via a photocurrent signal. We measure electric field-dependent Rabi oscillations of the neutral and charged exciton transitions in the ultrafast tunneling regime and demonstrate that tunneling induced dephasing (TID) of excitonic Rabi rotations is the major source for the intensity damping of Rabi oscillations in the low Rabi frequency, low temperature regime. Our results are in very good quantitative agreement with quantum-optical simulations revealing that TID can be used to precisely measure tunneling escape times and extract changes in the Coulomb binding energies for different charge configurations of the quantum dot. Finally, we demonstrate that for sub-picosecond electron tunneling escape TID of a coherently driven exciton transition facilitates ultrafast hole spin initialization with near-unity fidelity.