Phonon-induced transition between entangled and nonentangled photon emission in constantly driven quantum-dot--cavity systems

TL;DR

This paper investigates how phonon interactions in quantum dots affect the entanglement of photon pairs emitted in driven quantum-dot--cavity systems, revealing a phonon-induced transition from entangled to nonentangled states at low temperatures.

Contribution

It demonstrates that phonons induce a transition in photon entanglement, showing a qualitative change in entanglement behavior due to environmental interactions in quantum dots.

Findings

Phonons cause a transition from entangled to nonentangled photon emission below 30 K.

Entanglement decreases with temperature and driving strength, vanishing at a critical point.

The concurrence follows a power law with exponent one near the transition.

Abstract

Entangled photon pairs are essential for many applications in quantum technologies. Recent theoretical studies demonstrated that different types of entangled Bell states can be created in a constantly driven four-level quantum emitter-cavity system. Unlike other candidates for the realization of the four-level emitter, semiconductor quantum dots unavoidably interact with their environment, resulting in carrier-phonon interactions. Surprisingly, phonons change the entanglement of emitted photon pairs in a qualitative way, already at low temperatures on the order of 4 K. While one type of Bell state can still be generated using small driving strengths, the other type is suppressed due to phonon interactions in strongly-confined quantum dots. The degree of entanglement decreases with rising temperature and driving strength until it vanishes at a certain parameter value. Because it remains zero afterward, we encounter a phonon-induced transition between entangled and nonentangled photon emission that resembles a phase transition. The transition occurs at temperatures below 30 K and, independent of the driving strength, the concurrence as a function of the reduced temperature is found to obey a power law with exponent one near the transition point.