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A bright on-demand source of indistinguishable single photons at telecom wavelengths

Je‐Hyung Kim, Tao Cai, Christopher J. K. Richardson, Richard P. Leavitt, Edo Waks A

Published Nov 17, 2015• 0 citations
OpenAlex

Abstract

Long-distance quantum communication relies on the ability to efficiently generate and prepare single photons at telecom wavelengths. In many applications these photons must also be indistinguishable such that they exhibit interference on a beamsplitter, which implements effective photon-photon interactions. However, deterministic generation of indistinguishable single photons with high brightness remains a challenging problem. We demonstrate a telecom wavelength source of indistinguishable single photons using an InAs/InP quantum dot in a nanophotonic cavity. The cavity enhances the quantum dot emission, resulting in a nearly Gaussian transverse mode profile with high out-coupling efficiency exceeding 46%, leading to detected photon count rates that would exceed 1.5 million counts per second. We also observe Purcell enhanced spontaneous emission rate as large as 4. Using this source, we generate linearly polarized, high purity single photons at telecom-wavelength and demonstrate the indistinguishable nature of the emission using a two-photon interference measurement. Our results provide a promising approach to generate on-demand indistinguishable single photons at telecom wavelength for applications in quantum networking and quantum communication.

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Long-distance quantum communication relies on the ability to efficiently generate and prepare single photons at telecom wavelengths. In many applications these photons must also be indistinguishable such that they exhibit interference on a beamsplitter, which implements effective photon-photon interactions. However, deterministic generation of indistinguishable single photons with high brightness remains a challenging problem. We demonstrate a telecom wavelength source of indistinguishable single photons using an InAs/InP quantum dot in a nanophotonic cavity. The cavity enhances the quantum dot emission, resulting in a nearly Gaussian transverse mode profile with high out-coupling efficiency exceeding 46%, leading to detected photon count rates that would exceed 1.5 million counts per second. We also observe Purcell enhanced spontaneous emission rate as large as 4. Using this source, we generate linearly polarized, high purity single photons at telecom-wavelength and demonstrate the indistinguishable nature of the emission using a two-photon interference measurement. Our results provide a promising approach to generate on-demand indistinguishable single photons at telecom wavelength for applications in quantum networking and quantum communication.
Highly efficient single photon sources are important building blocks for optical quantum information processing. For practical use and long-distance quantum communication, single photons should have fiber-compatible telecom wavelengths. In addition, most quantum communication applications require high degree of indistinguishability of single photons, such that they exhibit interference on a beam splitter. However, deterministic generation of indistinguishable single photons with high brightness remains a challenging problem in particular at telecom wavelengths. We demonstrate a telecom wavelength source of indistinguishable single photons using an InAs/InP quantum dot in a nanophotonic cavity. To obtain the efficient single quantum dot emission, we employ the higher order mode in L3 photonic crystal cavity that shows a nearly Gaussian transverse mode profile and results in out-coupling efficiency exceeding 46 {\\%} and unusual bright single quantum dot emission exceeding 1.5 million counts per second at a detector. We also observe Purcell enhanced spontaneous emission rate as large as 4 and high linear polarization ratio of 0.96 for the coupled dots. Using this source, we generate high purity single photons at 1.3 ??m wavelength and demonstrate the indistinguishable nature of the emission using a two-photon interference measurement.
Long-distance quantum communication relies on the ability to efficiently generate and prepare single photons at telecom wavelengths. In many applications these photons must also be indistinguishable such that they exhibit interference on a beamsplitter, which implements effective photon-photon interactions. However, deterministic generation of indistinguishable single photons with high brightness remains a challenging problem. We demonstrate two-photon interference at telecom wavelengths using an InAs/InP quantum dot in a nanophotonic cavity. The cavity enhances the quantum dot emission, resulting in a nearly Gaussian transverse mode profile with high out-coupling efficiency exceeding 36% after multi-photon correction. We also observe Purcell enhanced spontaneous emission rate up to 4. Using this source, we generate linearly polarized, high purity single photons at 1.3 micron wavelength and demonstrate the indistinguishable nature of the emission using a two-photon interference measurement, which exhibits indistinguishable visibilities of 18% without post-selection and 67% with post-selection. Our results provide a promising approach to generate bright, deterministic single photons at telecom wavelength for applications in quantum networking and quantum communication.
On-demand single-photon sources operating at telecom wavelengths are crucial for quantum communication and photonic quantum technologies. In this work, we demonstrate high-purity, indistinguishable single-photon generation in the telecom O-band from an InAsP/InP nanowire quantum dot. We measured a single-photon purity of g2(0)=0.006±0.003 under above-band excitation. Furthermore, we characterize two-photon interference via Hong–Ou–Mandel measurements and achieve a photon indistinguishability of 81.1%±3.7% with a temporal postselection of a 300 ps time window and 5.6%±1.5% without temporal postselection. We estimate a first-lens source efficiency of ∼28%. These results highlight the potential of nanowire quantum dots as a promising source of telecom single photons for photonic quantum applications, offering deterministic positioning, efficient photon extraction, and scalable production.
Semiconductor quantum dots (QDs) enable the generation of single and entangled photons, useful for various applications in photonic quantum technologies. Specifically for quantum communication via fiber-optical networks, operation in the telecom C-band centered around 1550 \,nm is ideal. The direct generation of QD-photons in this spectral range and with high quantum-optical quality, however, remained challenging. Here, we demonstrate the coherent on-demand generation of indistinguishable photons in the telecom C-band from single QD devices consisting of InAs/InP QD-mesa structures heterogeneously integrated with a metallic reflector on a silicon wafer. Using pulsed two-photon resonant excitation of the biexciton-exciton radiative cascade, we observe Rabi rotations up to pulse areas of 4π4π4π and a high single-photon purity in terms of g(2)(0)=0.005(1)g^{(2)}(0)=0.005(1)g(2)(0)=0.005(1) and 0.015(1)0.015(1)0.015(1) for exciton and biexciton photons, respectively. Applying two independent experimental methods, based on fitting Rabi rotations in the emission intensity and performing photon cross-correlation measurements, we consistently obtain preparation fidelities at the πππ-pulse exceeding 80%\%%. Finally, performing Hong-Ou-Mandel-type two-photon interference experiments we obtain a photon-indistinguishability of the full photon wave packet of up to 35(3)%35(3)\%35(3)%, representing a significant advancement in the photon-indistinguishability of single photons emitted directly in the telecom C-band.
Telecom C-band single photons exhibit the lowest attenuation in optical fibers, enabling long-haul, quantum-secured communication. However, efficient coupling with optical fibers is crucial for these single photons to be effective carriers in long-distance transmission. We demonstrate an efficient fiber-coupled single photon source in the telecom C-band using InAs/InP quantum dots coupled to a tapered nanobeam. The tapered nanobeam structure facilitates directional emission that is mode-matched to a lensed fiber, resulting in a collection efficiency of up to 65% from the nanobeam to the single-mode fiber. Using this approach, we demonstrate single photon count rates of 575 ± 5 Kcps and a single photon purity of g (2) (0) = 0.015 ± 0.003. Additionally, we demonstrate Hong–Ou–Mandel interference from the emitted photons with a visibility of 0.84 ± 0.06. From these measurements, we determine a photon coherence time of 450 ± 20 ps, a factor of only 8.3 away from the lifetime limit. This work represents an important step toward the development of telecom C-band single-photon sources emitting bright, pure, and indistinguishable photons, which are necessary to realize fiber-based long-distance quantum networks.
Quantum dots are promising candidates for deterministic single-photon sources, yet achieving high photon indistinguishability at telecom wavelengths remains a critical challenge. Here, we report a quantum dot-based single-photon source operating in the telecommunications C-band that achieves a raw two-photon interference visibility of up to (91.7 ± 0.2)%, thus setting a new benchmark for indistinguishability in this spectral range. The device consists of an indium arsenide (InAs) quantum dot embedded within indium aluminum gallium arsenide (InAlGaAs) and integrated into a circular Bragg grating resonator. We explore multiple optical excitation schemes to optimize coherence and source performance. The demonstration of two-photon interference visibilities exceeding 90% from a quantum-dot emitter in the telecommunications C-band pushes solid-state single-photon sources further towards practical quantum communication and quantum networks.