On-demand semiconductor source of 780 nm single photons with controlled temporal wave packets

The ability to distribute quantum states and entanglement between remote systems in a quantum network provides new opportunities in secure communications, computational speed-up, and metrology [1]. In this framework, single... [ view full abstract ]

The ability to distribute quantum states and entanglement between remote systems in a quantum network provides new opportunities in secure communications, computational speed-up, and metrology [1]. In this framework, single photon sources are essential resources that allow matter qubits at stationary network nodes to be interconnected [2].

This project investigates the storage of single photons emitted from semiconductor quantum dots (QDs) in ensembles of rubidium atoms based on electromagnetically induced transparency (EIT). We have characterized a new type of self-assembled GaAs/AlGaAs quantum dots [3] that emit narrow-band single-photons around 780 nm (Fig.1(a)). Fine tuning of the photon carrier frequencies is achieved via strain and allows to address all hyperfine transitions of the rubidium D2 line (Fig.1(b)). Efficient storage also requires to control the spectro-temporal properties of the photons. Toward this goal, we placed the QDs in a magnetic field and used spontaneous spin-flip Raman transitions within the X¹⁺ exciton structure (Fig.1(c)) to generate on-demand single photons with tailored temporal profiles (Fig.1(d)) of durations exceeding the intrinsic exciton lifetime by up to three orders of magnitude [4]. All these properties make our single-photon source immediately suitable for investigating EIT-based single-photon storage and retrieval in dedicated broadband atomic memories [5].

[1] H.J. Kimble, “The quantum internet,” Nature 453, 1023 (2008).

[2] N. Sangouard et al., “Quantum repeaters based on atomic ensembles and linear optics,” Rev. Mod. Phys. 83, 33 (2011).

[3] J.-P. Jahn et al., “An artificial Rb atom in a semiconductor with lifetime-limited linewidth,” Phys. Rev. B 92, 245439 (2015).

[4] L. Béguin et al., “On-demand semiconductor source of 780 nm single photons with controlled temporal wave packets,” arXiv:1710.02490 (2017).

[5] J. Wolters et al., “Simple atomic quantum memory suitable for semiconductor quantum dot single photons,” Phys. Rev. Lett. 119 060502 (2017).

Figure: (a) Resonance fluorescence spectrum of an X¹⁺ in a droplet QD. (b) Rb D2 line transmission spectrum. (c) Energy levels of X¹⁺ subject to a magnetic field in the Faraday geometry. (d) Single Raman photon pulse-shaping. Top: laser driving transition ② with gaussian profiles. Bottom: single photon generated on transition ④ with gaussian wave packets.