Spin entanglement using coherent light and cavity-QED

TL;DR

This paper proposes a probabilistic scheme for entangling distant quantum dots using coherent light and cavity-QED, analyzing fidelity limits and strategies to mitigate decoherence effects for practical quantum communication.

Contribution

It introduces a novel entanglement generation method with analytical fidelity assessment and strategies to handle non-identical quantum dots and nuclear spin effects.

Findings

High fidelity entanglement is achievable with optimal parameters.

Decoherence from nuclear spins and non-identical dots can be mitigated.

The scheme is feasible for one- and two-sided cavities.

Abstract

A scheme for probabilistic entanglement generation between two distant single electron doped quantum dots, each placed in a high-Q microcavity, by detecting strong coherent light which has interacted dispersively with both subsystems and experienced Faraday rotation due to the spin selective trion transitions is discussed. In order to assess the applicability of the scheme for distant entanglement generation between atomic qubits proposed by T.D. Ladd et al. [New J. Phys. 8, 184 (2006)] to two distant quantum dots, one needs to understand the limitations imposed by hyperfine interactions of the quantum dot spin with the nuclear spins of the material and by non-identical quantum dots. Feasibility is displayed by calculating the fidelity for Bell state generation analytically within an approximate framework. The fidelity is evaluated for a wide range of parameters and different pulse lengths, yielding a trade-off between signal and decoherence, as well as a set of optimal parameters. Strategies to overcome the effect of non-identical quantum dots on the fidelity are examined and the timescales imposed by the nuclear spins are discussed, showing that efficient entanglement generation is possible with distant quantum dots. In this context, effects due to light hole transitions become important and have to be included. The scheme is discussed for one- as well as for two-sided cavities, where one must be careful with reflected light which carries spin information. The validity of the approximate method is checked by a more elaborate semiclassical simulation which includes trion formation.