Waveguide superconducting single-photon detectors for integrated quantum photonic circuits

Abstract

A linear-optics quantum computer 5 requires hundreds to thousands of single-photon components including sources, detectors and interferometers, which is obviously only feasible in an integrated circuit.Even the small-scale circuits needed in quantum repeaters 2 would greatly benefit from monolithic integration in view of the improved stability and coupling efficiency attainable in a chip. A very large experimental research activity has been dedicated to the development of single-photon sources based on III-V semiconductors 10 , in view of large-scale integration, and to passive quantum circuits based on silica-onsilicon 6 and on laser-micromachined glass 8,9 , but a clear approach towards a fully integrated photonic network including sources and detectors has not been proposed. This is in large part due to the complexity of most single-photon detector technologies -for example, the complex device structures associated to avalanche photodiodes are not easily compatible with the integration of low-loss waveguides and even less of sources. Transition-edge sensors may be suited for integration 11 , but they are plagued by very slow response times (leading to maximum counting rates in the tens of kHz range) and require cooling down to <100 mK temperatures. Here we propose a platform for the full integration of quantum photonic components on the same chip. It is based on the mature III-V semiconductor technology and comprises ( Fig. 1(a) ) waveguide single-photon sources based on InAs quantum dots (QDs), GaAs/AlGaAs ridge waveguides, Mach-Zehnder interferometers using directional couplers or multimode-interference couplers, and 3 waveguide detectors based on superconducting nanowires. Efficient single-photon emission from QDs in a waveguide can be obtained by using photonic crystals (PhCs), e.g. in a cavity side-coupled to a waveguide 12 or using the slow-light regime in PhC waveguides 13 , and the photons can then be transferred to ridge waveguides using tapers. Photons emitted by distinct QDs can be made indistinguishable by using electric fields to control the exciton energy 14 . The high index contrast available in the GaAs/AlGaAs system allows circuits with short bending radii, therefore more compact than in the silica platform 6 , while the large electrooptic coefficient of GaAs enables compact modulators operating at GHz frequencies. In this letter we report the key missing component, a single-photon detector integrated with GaAs waveguides. Our waveguide single-photon detectors (WSPDs) are based on the principle of photon-induced hot-spot creation in ultranarrow superconducting NbN wires, which is also used in nanowire superconducting single-photon detectors 15 (SSPDs) and can provide ultrahigh sensitivity at telecommunication wavelengths, high counting rates, broad spectral response and high temporal resolution due to low jitter values. In our design (see Fig. 1(b)), the wires are deposited and patterned on top of a GaAs ridge waveguide, in order to sense the evanescent field on the surface. Four NbN nanowi...

Quantum dot spontaneous emission control in a ridge waveguide

“…8,9 On the detection side, a superconducting nanowire located in the evanescent field of a ridge waveguide can be used to detect guided photons with low noise and high efficiency. 10 Despite these promising advances, the tailoring of QD spontaneous emission by ridge waveguides has not yet been investigated experimentally.…”

Optically probing the detection mechanism in a molybdenum silicide superconducting nanowire single-photon detector

“…Their low dark count rate, fast response time, small jitter, and high efficiency favour their use in various demanding quantum optics applications such as quantum key distribution, 3 quantum networking, 4 device-independent quantum information processing 5 and deep-space optical communication. 6 Notably, SNSPDs can be integrated into photonic circuits, 7,8 and their applications extend beyond quantum optics, including light detection and ranging, 9 integrated circuit testing, 10 and fiber optic sensing. 11 One recent important advance in the SNSPD field has been the introduction of amorphous superconductors such as tungsten silicide (WSi), 12 molybdenum silicide (MoSi) 13,14 and molybdenum germanium (MoGe).…”

Superconducting Optoelectronic Circuits for Neuromorphic Computing

“…Such detectors have low signal-to-noise ratio, requiring operation with significantly higher optical powers than if superconducting detectors are employed. While it may be possible to develop neuromorphic technology based on many of these detectors, we have chosen for this article to focus on superconducting nanowire single photon detectors (SNSPDs) due to the high efficiencies (> 90%) [39] at wavelengths below the Si bandgap, simple on-chip waveguide integration [40][41][42][43][44][45][46], compact size, and speed. While operation at cryogenic temperatures imparts a fixed energy cost, the energy cost per operation is significantly decreased by allowing integration with superconducting electronics.…”