From strong to weak temperature dependence of the two-photon entanglement resulting from the biexciton cascade inside a cavity

Titelangaben

Seidelmann, Tim ; Ungar, Florian ; Cygorek, Moritz ; Vagov, Alexei ; Barth, Andreas M. ; Kuhn, Tilmann ; Axt, Vollrath Martin:
From strong to weak temperature dependence of the two-photon entanglement resulting from the biexciton cascade inside a cavity.
In: Physical Review B. Bd. 99 (2019) Heft 24 . - 245301.
ISSN 0163-1829
DOI: https://doi.org/10.1103/PhysRevB.99.245301

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Abstract

We investigate the degree of entanglement quantified by the concurrence of photon pairs that are simultaneously emitted in the biexciton-exciton cascade from a quantum dot in a cavity. Four dot-cavity configurations are compared that differ with respect to the detuning between the cavity modes and the quantum dot transitions, corresponding to different relative weights of direct two-photon and sequential single-photon processes. The dependence of the entanglement on the exciton fine-structure splitting δ is found to be significantly different for each of the four configurations. For a finite splitting and low temperatures, the highest entanglement is found when the cavity modes are in resonance with the two-photon transition between the biexciton and the ground state and, in addition, the biexciton has a finite binding energy of a few meV. However, this widely used configuration is rather strongly affected by phonons such that other dot-cavity configurations, that are commonly regarded as less suited for obtaining high degrees of entanglement, become more favorable already at temperatures on the order of 10K and above. If the cavity modes are kept in resonance with one of the exciton-to-ground-state transitions and the biexciton binding energy is finite, the entanglement drastically drops for positive δ with rising temperatures when T is below ≃4K, but is virtually independent of the temperature for higher T.