Coherent light scattering from a telecom C-band quantum dot

Abstract

Quantum networks have the potential to transform secure communication via quantum key distribution and enable novel concepts in distributed quantum computing and sensing. Coherent quantum light generation at telecom wavelengths is fundamental for fibre-based network implementations, but Fourier-limited emission and subnatural linewidth photons have so far only been reported from systems operating in the visible to near-infrared wavelength range. Here, we use InAs/InP quantum dots to demonstrate photons with coherence times much longer than the Fourier limit at telecom wavelength via elastic scattering of excitation laser photons. Further, we show that even the inelastically scattered photons have coherence times within the error bars of the Fourier limit. Finally, we make direct use of the minimal attenuation in fibre for these photons by measuring two-photon interference after 25 km of fibre, demonstrating finite interference visibility for photons emitted about 100,000 excitation cycles apart.

Efficient, Indistinguishable Telecom C-Band Photons using a Tapered Nanobeam Waveguide

“…This value is similar to the best reported results for C-band single photon sources under nonresonant and resonant excitation (440 ± 45 ps and 447 ± 15 ps). 17,18 A high coherence time could enable high-fidelity quantum information processing and increase the efficiency of repeater-based quantum communication systems at telecom C-band wavelengths. 35 We also evaluated the visibility of the indistinguishable photons based on coincidence counts for the copolarized and cross-polarized photons.…”

“…5,6 Among these methods, single photon sources based on semiconductor quantum dots are considered most promising due to their high brightness, 7,8 high purity, 7,9 and indistinguishability. 10−12 For example, InAs/InP quantum dots emit single photons in the telecom C-band spectrum, 9,11−18 which have been extracted utilizing various device structures, such as mesa structures, 12 planar cavities, 17 nanowires, 19 and photonic crystal cavities. 8 However, more efficient coupling to the optical fiber is needed to collect the telecom C-band single photon emission with high efficiency for long-distance quantum networks.…”

“…A telecom single-photon source operating around 1,550 nm (C-band) is essential for fiber-based quantum communication networks to minimize transmission loss in the silica fiber. Various approaches have been explored to realize single-photon sources within this spectral window, including spontaneous parametric down-conversion, , as well as materials such as carbon nanotubes, and semiconductor quantum dots. , Among these methods, single photon sources based on semiconductor quantum dots are considered most promising due to their high brightness, , high purity, , and indistinguishability. − For example, InAs/InP quantum dots emit single photons in the telecom C-band spectrum, ,− which have been extracted utilizing various device structures, such as mesa structures, planar cavities, nanowires, and photonic crystal cavities . However, more efficient coupling to the optical fiber is needed to collect the telecom C-band single photon emission with high efficiency for long-distance quantum networks.…”

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

“…To date, application-oriented research on QD-based single-photon sources in the telecom C-band has been limited to incoherent excitation schemes while investigations of coherent pumping schemes have put the focus more on fundamental research. 16,17,33,34 However, in terms of application-ready brightness under coherent pumping, a rate of 500 kHz under continuous-wave excitation has not yet been surpassed, 34 underlining the significance of the implementation in this work. Next, the photon indistinguishability is investigated.…”

“…On the basis of this value, the detected count rate (CR raw = 6.50 MHz), and the detection efficiency (76.8%, a detailed description of the efficiencies can be found in section 4 of the Supporting Information), an application-ready rate of polarized single photons with a CR end of 8.14 MHz coupled to a single-mode fiber, corresponding to an end-to-end efficiency (that corresponds to the total system efficiency in ref ) η end of 5.36%, is found. To date, application-oriented research on QD-based single-photon sources in the telecom C-band has been limited to incoherent excitation schemes while investigations of coherent pumping schemes have put the focus more on fundamental research. ,,, However, in terms of application-ready brightness under coherent pumping, a rate of 500 kHz under continuous-wave excitation has not yet been surpassed, underlining the significance of the implementation in this work.…”