Coherently and Incoherently Pumped Telecom C-Band Single-Photon Source with High Brightness and Indistinguishability.

Long-range, terrestrial quantum networks require high-brightness single-photon sources emitting in the telecom C-band for maximum transmission rates. For solid-state quantum emitters, the underlying pumping process, i.e., coherent or incoherent excitation schemes, impacts several photon properties such as photon indistinguishability, single-photon purity, and photon number coherence. These properties play a major role in quantum communication applications, the latter in particular for quantum cryptography. Here, we present a versatile telecom C-band single-photon source that is operated coherently and incoherently using two complementary pumping schemes. The source is based on a quantum dot coupled to a circular Bragg grating cavity, whereas coherent (incoherent) operation is performed via the novel SUPER scheme (phonon-assisted excitation). In this way, high end-to-end-efficiencies (ηend) of 5.36% (6.09%) are achieved simultaneously with a small multiphoton contribution g(2)(0) of 0.076 ± 0.001 [g(2)(0) of 0.069 ± 0.001] for coherent (incoherent) operation.

Deterministic storage and retrieval of telecom light from a quantum dot single-photon source interfaced with an atomic quantum memory.

A hybrid interface of solid-state single-photon sources and atomic quantum memories is a long sought-after goal in photonic quantum technologies. Here, we demonstrate deterministic storage and retrieval of light from a semiconductor quantum dot in an atomic ensemble quantum memory at telecommunications wavelengths. We store single photons from an indium arsenide quantum dot in a high-bandwidth rubidium vapor-based quantum memory, with a total internal memory efficiency of (12.9 ± 0.4)%. The signal-to-noise ratio of the retrieved light field is 18.2 ± 0.6, limited only by detector dark counts.

Bright Purcell Enhanced Single-Photon Source in the Telecom O-Band Based on a Quantum Dot in a Circular Bragg Grating.

The combination of semiconductor quantum dots with photonic cavities is a promising way to realize nonclassical light sources with state-of-the-art performances regarding brightness, indistinguishability, and repetition rate. Here we demonstrate the coupling of InGaAs/GaAs QDs emitting in the telecom O-band to a circular Bragg grating cavity. We demonstrate a broadband geometric extraction efficiency enhancement by investigating two emission lines under above-band excitation, inside and detuned from the cavity mode, respectively. In the first case, a Purcell enhancement of 4 is attained. For the latter case, an end-to-end brightness of 1.4% with a brightness at the first lens of 23% is achieved. Using p-shell pumping, a combination of high count rate with pure single-photon emission (g(2)(0) = 0.01 in saturation) is achieved. Finally, a good single-photon purity (g(2)(0) = 0.13) together with a high detector count rate of 191 kcps is demonstrated for a temperature of up to 77 K.