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arXiv:1703.10536 · Scientific Reports

A stand-alone fiber-coupled single-photon source

Alexander Schlehahn, Sarah Fischbach, Ronny Schmidt, Arsenty Kaganskiy, André Strittmatter, Sven Rodt, Tobias Heindel, Stephan Reitzenstein

Published Jan 16, 2018• 99 citations
arXivHTMLPDF

Abstract

Abstract In this work, we present a stand-alone and fiber-coupled quantum-light source. The plug-and-play device is based on an optically driven quantum dot delivering single photons via an optical fiber. The quantum dot is deterministically integrated in a monolithic microlens which is precisely coupled to the core of an optical fiber via active optical alignment and epoxide adhesive bonding. The rigidly coupled fiber-emitter assembly is integrated in a compact Stirling cryocooler with a base temperature of 35 K. We benchmark our practical quantum device via photon auto-correlation measurements revealing g(2)(0) = 0.07 ± 0.05 under continuous-wave excitation and we demonstrate triggered non-classical light at a repetition rate of 80 MHz. The long-term stability of our quantum light source is evaluated by endurance tests showing that the fiber-coupled quantum dot emission is stable within 4% over several successive cool-down/warm-up cycles. Additionally, we demonstrate non-classical photon emission for a user-intervention-free 100-hour test run and stable single-photon count rates up to 11.7 kHz with a standard deviation of 4%.

DOI
10.1038/s41598-017-19049-4

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Abstract In this work, we present a stand-alone and fiber-coupled quantum-light source. The plug-and-play device is based on an optically driven quantum dot delivering single photons via an optical fiber. The quantum dot is deterministically integrated in a monolithic microlens which is precisely coupled to the core of an optical fiber via active optical alignment and epoxide adhesive bonding. The rigidly coupled fiber-emitter assembly is integrated in a compact Stirling cryocooler with a base temperature of 35 K. We benchmark our practical quantum device via photon auto-correlation measurements revealing g(2)(0) = 0.07 ± 0.05 under continuous-wave excitation and we demonstrate triggered non-classical light at a repetition rate of 80 MHz. The long-term stability of our quantum light source is evaluated by endurance tests showing that the fiber-coupled quantum dot emission is stable within 4% over several successive cool-down/warm-up cycles. Additionally, we demonstrate non-classical photon emission for a user-intervention-free 100-hour test run and stable single-photon count rates up to 11.7 kHz with a standard deviation of 4%.
We report a 'plug and play' single-photon source based on single quantum dots with an integrated optical fibre output. We attach an optical fibre to the sample surface in order to measure single-dot photoluminescence, which avoids the light coupling between quantum dots and free space. The excitation light (a HeNe Laser) is coupled into the optical fibre to excite the quantum dots, and the emitted photoluminescence is collected with same optical fibre. To verify the emission of single photons, correlation measurements of the luminescence were performed using a Hanbury Brown and Twiss setup with a 50/50 beamsplitter and two single-photoncounting avalanche photodiodes. Clear antibunching with the second-order correlation function at zero time delay less than 0.1 indicates single-photon emission. The devices are stable, and reproducible for an arbitrarily long time, which is very promising for real implementations of quantum key distribution and linear optical quantum computation.
We demonstrate an ultra-compact source of on-demand, maximally entangled photon pairs using single GaAs quantum dots embedded in monolithic microlenses coupled to a lensed single-mode fiber. A 3D-printed micro-objective with a numerical aperture of 0.6 enables efficient fiber coupling and near-diffraction-limited performance with 604(16) nm resolution directly in the cryogenic environment at 3.8 K. The system achieves high single-photon emission rates [392(20) kHz] and purities [99.2(5)%] using two-photon resonant excitation. Leveraging the exciton–biexciton cascade, it produces near-maximally entangled photon pairs with peak entanglement negativities of 2n = 0.96 ± 0.02. The presented quantum light source combines state-of-the-art performance and long-term stability with a dramatically reduced system footprint, making it well-suited for seamless industrial integration.
Deterministic solid-state quantum light sources are key building blocks in photonic quantum technologies. While several proof-of-principle experiments of quantum communication using such sources have been realized, all of them required bulky setups. Here, we evaluate for the first time the performance of a compact and stand-alone fiber-coupled single-photon source emitting in the telecom O-band (1321 1321\,1321nm) for its application in quantum key distribution (QKD). For this purpose, we developed a compact 19'' rack module including a deterministically fiber-coupled quantum dot single-photon source integrated into a Stirling cryocooler, a pulsed diode laser for driving the quantum dot, and a fiber-based spectral filter. We further employed this compact quantum light source in a QKD testbed designed for polarization coding via the BB84 protocol resulting in g(2)(0)=0.10±0.01g^{(2)}(0) = 0.10\pm0.01g(2)(0)=0.10±0.01 and a raw key rate of up to (4.72±0.13) (4.72\pm0.13)\,(4.72±0.13)kHz using an external laser for excitation. In this setting we investigate the achievable performance expected in full implementations of QKD. Using 2D temporal filtering on receiver side, we evaluate optimal parameter settings for different QKD transmission scenarios taking also finite key size effects into account. Using optimized parameter sets for the temporal acceptance time window, we predict a maximal tolerable loss of 23.19 23.19\,23.19dB. Finally, we compare our results to previous QKD systems using quantum dot single-photon sources. Our study represents an important step forward in the development of fiber-based quantum-secured communication networks exploiting sub-Poissonian quantum light sources.
Fiber-based long-haul quantum communication would greatly benefit from a robust and deterministically integrated source of quantum states. Here, we report the design, fabrication, and optical characterization of In As / In P quantum dots in the In P H1 point-defect 2D photonic crystal cavity, integrated with a standard single-mode fiber employing microtransfer printing. The device is placed in a compact cryocooler maintaining a cryogenic temperature of 15 K, and it exhibits a low multiphoton contribution to emission, with g ( 2 ) ( 0 ) = 0.14 ( 14 ) in the all-fiber-based optical link between two laboratory nodes. In this way, we demonstrate a plug-and-play all-fiber single-photon source operating in the third telecom window, where standard telecommunication fiber networks can be used as a low-loss medium.
The authors report a “plug and play” source of single photons, with full integration to a single-mode optical fiber. One end of the fiber is attached to the top of an InGaAs∕GaAs quantum dot wafer. The other end is connected via a wavelength-division multiplexing system to two separate fibers: one for carrying excitation light and the other for emitted light. A Hanbury-Brown and Twiss [Nature (London) 77, 27 (1956)] measurement was performed on the emission from single excitons recombining in the quantum dots. A second-order correlation function at zero time delay of approximately 0.01 indicates a nearly ideal source of single photons. The maximum variation of peak position over 24days is less than 0.1nm.
A highly pure and stable single-photon source is prepared that comprises a well-designed pillar array, in which each pillar contains only a few InAs quantum dots. A nano-pillar in this array is in direct contact with a fiber end surface and cooled in a liquid-He bath. Auto-correlation measurements show that this source provides an average g(2)(0) value of 0.0174 in the measured excitation-power range. This photon source and fiber coupling are quite rigid against external disturbances such as cooling-heating cycles and vibration, with long-term stability.