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arXiv 1902.01683cond-mat.mes-hall
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腔中双激子级联产生的双光子纠缠对温度的依赖性由强到弱

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

Tim Seidelmann, Florian Ungar, Moritz Cygorek, Alexei Vagov, Andreas M. Barth, Tilmann Kuhn, Vollrath Martin Axt

摘要:

我们研究了腔中量子点双激子-激子级联中同时发射的光子对的纠缠度。四个点腔配置进行了比较,不同的腔模式和量子点跃迁之间的失谐,对应于不同的相对权重的直接双光子和顺序单光子过程。的依赖激子精细结构分裂$δ$的纠缠被发现是显着不同的四种配置。对于一个有限的分裂和低温,最高的纠缠被发现时,腔模式与双激子和基态之间的双光子跃迁共振,此外,双激子具有有限的结合能的几毫电子伏。然而,这种广泛使用的配置是相当强烈的声子的影响,使得其他点腔配置,通常被认为是不太适合获得高程度的纠缠,变得更有利的已经在10 K和以上的温度的顺序。如果腔模保持与激子到基态的跃迁之一共振,并且双激子结合能是有限的,则当$T$低于$\simeq$ 4 K时,正$δ$的纠缠随着温度的升高而急剧下降,但是对于较高的$T$,纠缠几乎与温度无关。

英文摘要:

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 10 K 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 $\simeq$ 4 K, but is virtually independent of the temperature for higher $T$.

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