Two-Photon Excitation Sets Limit to Entangled Photon Pair Generation from Quantum Emitters

Abstract

Entangled photon pairs are key to many novel applications in quantum technologies. Semiconductor quantum dots can be used as sources of on-demand, highly entangled photons. The fidelity to a fixed maximally entangled state is limited by the excitonic fine-structure splitting. This work demonstrates that, even if this splitting is absent, the degree of entanglement cannot reach unity when the excitation pulse in a two-photon resonance scheme has a finite duration. The degradation of the entanglement has its origin in a dynamically induced splitting of the exciton states caused by the laser pulse itself. Hence, in the setting explored here, the excitation process limits the achievable concurrence for entangled photons generated in an optically excited four-level quantum emitter.

7 pages, 3 figures, supplemental material

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• A multipair-free source of entangled photons in the solid state
• Swing-up dynamics in quantum emitter cavity systems
• Temperature-independent almost perfect photon entanglement from quantum dots via the SUPER scheme
• Two-photon excitation with finite pulses unlocks pure dephasing-induced degradation of entangled photons emitted by quantum dots
• Signatures of the Optical Stark Effect on Entangled Photon Pairs from Resonantly-Pumped Quantum Dots
• Hyperfine-interaction limits polarization entanglement of photons from semiconductor quantum dots
• Time-bin entanglement in the deterministic generation of linear photonic cluster states
• Theory of time-bin entangled photons from quantum emitters
• Towards Photon-Number-Encoded High-dimensional Entanglement from a Sequentially Excited Quantum Three-Level System
• Qubit-environment entanglement in time-dependent pure dephasing
• Dynamically Dressed States of a Quantum Four-Level System