On-De­mand In­dis­tin­guish­able and En­tangled Photons Us­ing Tailored Cav­ity Designs

 |  TRR 142 - Maßgeschneiderte nichtlineare Photonik: Von grundlegenden Konzepten zu funktionellen Strukturen

Quantum emitters that produce both indistinguishable and polarization-entangled photons are essential prerequisites for photon-based quantum information processing.

Bauch et al. investigate the cavity-assisted generation of highly indistinguishable and at the same time entangled photon pairs from semiconductor quantum dots. The authors combine Maxwell simulations of the optical resonator with quantum simulations of the quantum dot and find optimal design strategies and parameters for the implementation of such emitter devices for quantum information technologies.

While the degenerate two-photon emission from a biexciton offers high polarization entanglement but low indistinguishability, single photons from the biexciton-exciton-ground cascade usually exhibit the opposite characteristics, primarily due to the biexciton-exciton lifetime ratio.

Addressing this challenge involves artificially reducing the biexciton's lifetime. In this study, the authors achieve this reduction by introducing a circular Bragg grating cavity into the system, thereby Purcell enhancing the biexciton-exciton transition and consequently decreasing the biexciton's lifetime.

The cavity is optimized through Maxwell simulations, and the quantum properties of the emitted photons are simulated using a comprehensive quantum mechanical description. The resulting photons exhibit high indistinguishability while retaining a high degree of polarization entanglement.

Link to the publication: https://doi.org/10.1002/qute.202300142

 

Sketch of the QD-Cavity system (a) with the electronic four level system of the biexciton and (b) artistic representation of a circular bragg grating (CBG) cavity with the excitation of the QD (yellow) and emission of photons (orange,blue).
Sketch of the QD-Cavity system (a) with the electronic four level system of the biexciton and (b) artistic representation of a circular bragg grating (CBG) cavity with the excitation of the QD (yellow) and emission of photons (orange,blue).
(a) Rendered image of the CBG cavity. (b) Sideview of the cavity construction and optimization parameters. The additional variational degree of freedom on the first trench width W1 allows for fine tuning of the cavity.
(a) Rendered image of the CBG cavity. (b) Sideview of the cavity construction and optimization parameters. The additional variational degree of freedom on the first trench width W1 allows for fine tuning of the cavity.
Sweep of the Purcell enhancement (X-Axis) and the Cavity Coupling (Y-Axis). (a,d) Indistinguishability of the emitted exciton photon. (b,e) Indistinguishability of the emitted biexciton photon. (c,f) Concurrence (entanglement) of both photons. The Maxwell optimized cavity is marked with an 'x' in panel (e).
Sweep of the Purcell enhancement (X-Axis) and the Cavity Coupling (Y-Axis). (a,d) Indistinguishability of the emitted exciton photon. (b,e) Indistinguishability of the emitted biexciton photon. (c,f) Concurrence (entanglement) of both photons. The Maxwell optimized cavity is marked with an 'x' in panel (e).
Cover picture of the magazine Advanced Quantum Technologies Vol.7 No. 1, January 2024
Cover picture of the magazine Advanced Quantum Technologies Vol.7 No. 1, January 2024

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