Quantum-dot single photon source performance with off-resonant pulse preparation schemes

TL;DR

This paper compares off-resonant pulse schemes for quantum dot single photon sources, highlighting their performance, robustness, and phonon interaction effects, with implications for improving quantum photonic devices.

Contribution

It evaluates three off-resonant excitation schemes, providing insights into their efficiency, phonon dephasing effects, and robustness, advancing quantum dot SPS technology.

Findings

Dichromatic pulses suffer from phonon-induced dephasing reducing performance by up to 50%.

NARP and SUPER pulses maintain excellent performance with less phonon coupling.

NARP pulses are more robust against pulse variance despite being more complex to implement.

Abstract

The preparation of photonic qubits in the excited state is an integral part of the performance of an on-demand single photon source (SPS). Conventional resonant excitation, an excellent approach to maximize the coherence and indistinguishability of the SPS, often requires polarization filtering to remove the pump signal and isolate the qubit emission, but this results in an inherent 50\% hit to the efficiency. Recent excitation schemes strategically try to exploit pulses that excite the qubit while avoiding spectral overlap to bypass this required filtering. In this work, we compare three such pumping schemes to quantify the important SPS figures-of-merit for off-resonant quantum dot schemes, using: (i) a symmetrically detuned dichromatic pulse, (ii) a notch-filtered adiabatic rapid passage (NARP) pulse, and (iii) a swing up of the quantum emitter population (SUPER) pulse. Due to large instantaneous pulse strengths, the dichromatic pulse suffers from phonon-induced dephasing which can lower the SPS performance by up to 50\%. In contrast, the NARP and SUPER pulses are shielded from phonon coupling to differing degrees but both maintain excellent SPS performance. The SUPER pulse can lose significant efficiency if there is variance in its constituent pulses' amplitude, pulse width, or frequency, while the NARP pulse, though potentially more difficult to realize in experiments, is robust against variance in the pulse preparation.