Dresden 2014 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 38: Quantum light sources based on solid state systems: Status and visions I (Focus session with TT)
HL 38.3: Talk
Tuesday, April 1, 2014, 10:15–10:30, POT 251
Feedback-Enhanced Entanglement of Photons from a Biexciton Cascade — •Sven Moritz Hein1, Franz Schulze1, Alexander Carmele2, and Andreas Knorr1 — 1Technische Universität Berlin, Institut für theoretische Physik, Nichtlineare Optik und Quantenelektronik, Hardenbergstraße 36, 10623 Berlin, Germany — 2Institut für Quantenoptik und Quanteninformation, Technikerstraße 21a, 6020 Innsbruck, Austria
Coherent quantum feedback [1] is a method to control and stabilize quantum-mechanical systems by the use of a feedback mechanism that does not rely on measurement, but is completely quantum-mechanical itself. We utilize such a feedback scheme to enhance the entanglement of photons from a biexciton cascade in a quantum dot. The achievable photon entanglement is usually diminished substantially by exciton fine-structure splitting. We demonstrate that it is possible to increase photon entanglement by feeding the emitted light back into the quantum dot after a certain feedback time, e.g. by using a mirror at a specific distance from the emitter [2]. The complex interplay between original and reflected field modifies the emission spectrum in a way that the achievable entanglement is strongly enhanced. We present a full quantum-mechanical theory of the system, including the feedback-induced modification of the photon mode continuum. We analyze the influence of feedback delay and phase and discuss the involved mechanisms in detail.
[1] S. Lloyd, Phys. Rev. A 62, 022108 (2000).
[2] A. Carmele et al., Phys. Rev. Lett. 110, 013601 (2012).