Deterministic Photon Pairs and Coherent Optical Control of a Single Quantum Dot

Harishankar Jayakumar, Ana Predojević, Tobias Huber, Thomas Kauten, Glenn S. Solomon, and Gregor Weihs

Phys. Rev. Lett. 110, 135505 – Published 26 March 2013

Abstract

The strong confinement of semiconductor excitons in a quantum dot gives rise to atomlike behavior. The full benefit of such a structure is best observed in resonant excitation where the excited state can be deterministically populated and coherently manipulated. Because of the large refractive index and device geometry it remains challenging to observe resonantly excited emission that is free from laser scattering in III/V self-assembled quantum dots. Here we exploit the biexciton binding energy to create an extremely clean single photon source via two-photon resonant excitation of an $InAs / GaAs$ quantum dot. We observe complete suppression of the excitation laser and multiphoton emissions. Additionally, we perform full coherent control of the ground-biexciton state qubit and observe an extended coherence time using an all-optical echo technique. The deterministic coherent photon pair creation makes this system suitable for the generation of time-bin entanglement and experiments on the interaction of photons from dissimilar sources.

Received 24 October 2012

DOI:https://doi.org/10.1103/PhysRevLett.110.135505

Authors & Affiliations

Harishankar Jayakumar^1,*, Ana Predojević^1,†, Tobias Huber¹, Thomas Kauten¹, Glenn S. Solomon², and Gregor Weihs¹

¹Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
²Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Gaithersburg, Maryland 20849, USA

^*harishankar@uibk.ac.at
^†ana.predojevic@uibk.ac.at

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Vol. 110, Iss. 13 — 29 March 2013

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Images

Figure 1
Photoluminescence under resonant two-photon excitation. (a) Photoluminescence spectra of the $V$ -polarized cascade and a suppressed $H$ -polarized excitation laser. (b), (c) Emission from $V$ and $H$ -polarized cascades under $H$ -polarized excitation. Solid lines are Gaussian fits to the data showing the fine structure splitting of the exciton states.Reuse & Permissions
Figure 2
Excitation-emission scheme and experimental setup. (a) Energy level scheme. A pulsed laser with energy $E_{exc} = (| b ⟩ - | g ⟩) / 2$ and linearly polarized ( $H$ ) along the cleaved edge of the sample, coherently couples the ground ( $| g ⟩$ ) and the biexciton ( $| b ⟩$ ) states through a virtual level (dashed gray line). Biexciton recombination takes place through the intermediate exciton states ( $| x_{H, V} ⟩$ ) emitting biexciton ( $X X_{H, V}$ ) and exciton ( $X_{H, V}$ ) photons. Biexciton binding energy ( $E_{b}$ ) results in $(| x_{H, V} ⟩ - | g ⟩) > E_{exc} > (| b ⟩ - | x_{H, V} ⟩)$ . (b) Experimental setup: consists of excitation, collection, and detection part. Pump interferometer output fiber couplers labeled 1 and 2 collect double pulses and triple pulses, respectively, for coherent control experiments. A glass phase plate (PP) on the short arm of the interferometer controls the intensity of the echo pulse.Reuse & Permissions
Figure 3
(a) Power dependence of the biexciton emission probability for various excitation laser detunings $[E_{exc} - (| b ⟩ - | g ⟩) / 2] / ℏ$ from the two-photon resonance. Solid lines are simulations. (b) Power dependence of biexciton and exciton photons under incoherent two-photon excitation, far detuned from two-photon biexciton state resonance towards lower energy. (c) Photoluminescence spectra from the 3 mW measurement point of (b).Reuse & Permissions
Figure 4
(a), (b) Autocorrelation measurement of the $V$ -polarized biexciton and exciton photons in resonant excitation. (c) Cross correlation coincidence counts between the biexciton (start) and exciton (stop) photons. All the data shown here are presented without background subtraction.Reuse & Permissions
Figure 5
(a) Visibility of Ramsey interference in the two-pulse (green open squares) and three-pulse echo sequence (red open circles) coherent control experiment monitored with the biexciton photons. (b) Laser interference at 0 ps coarse delay. (c) Ramsey interference fringes at coarse delays of 8, 107, and 240 ps. (d) Ramsey interference fringes after the echo pulse at coarse delays of 45, 339, and 472 ps. Both Ramsey and echo sequence measurements do not reach zero visibility due to the shot noise of $\sqrt{N}$ counts. Error bars for the shot noise are visible only for long delays.Reuse & Permissions

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