Double-Pulse Generation of Indistinguishable Single Photons with Optically Controlled Polarization

TL;DR

This paper presents a novel method to generate indistinguishable single photons with controllable polarization using off-resonant laser pulses in quantum dots, achieving high purity and indistinguishability without polarization filtering losses.

Contribution

The authors introduce a two-pulse off-resonant excitation scheme combined with magnetic fields to control photon polarization, improving efficiency and photon quality in quantum dot sources.

Findings

Achieved 99.6% single-photon purity

Generated photons with 85% indistinguishability

Controlled polarization degree of 101% using optical methods

Abstract

Single-photon sources play a key role in photonic quantum technologies. Semiconductor quantum dots can emit indistinguishable single photons under resonant excitation. However, the resonance fluorescence technique typically requires cross-polarization filtering which causes a loss of the unpolarized quantum dot emission by 50%. To solve this problem, we demonstrate a method to generate indistinguishable single photons with optically controlled polarization by two laser pulses off-resonant with neutral exciton states. This scheme is realized by exciting the quantum dot to the biexciton state and subsequently driving the quantum dot to an exciton eigenstate. Combining with magnetic field, we demonstrated the generation of photons with optically controlled polarization (polarization degree of 101(2)%), laser-neutral exciton detuning up to 0.81 meV, high single-photon purity (99.6(1)%) and indistinguishability (85(4)%). Laser pulses can be blocked using polarization and spectral filtering. Our work makes an important step towards indistinguishable single-photon sources with near-unity collection efficiency.