Scalable, high speed data transfer between cryogenic (0.1-4 K) and room temperature environments is instrumental in a broad range of fields including quantum computing, superconducting electronics, single photon imaging and space-based communications. A promising approach to overcome the limitations of conventional wire-based readout is the use of optical fiber communication. Optical fiber presents a 100-1,000x lower heat load than conventional electrical wiring, relaxing the requirements for thermal anchoring, and is also immune to electromagnetic interference, which allows routing of sensitive signals with improved robustness to noise and crosstalk. Most importantly, optical fibers allow for very high bandwidth densities (in the Tbps/mm$^2$ range) by carrying multiple signals through the same physical fiber (Wavelength Division Multiplexing, WDM). Here, we demonstrate for the first time optical readout of a superconducting nanowire single-photon detector (SNSPD) directly coupled to a CMOS photonic modulator, without the need for an interfacing device. By operating the modulator in the forward bias regime at a temperature of 3.6 K, we achieve very high modulation efficiency (1000-10,000 pm/V) and a low input impedance of 500 $Ω$ with a low power dissipation of 40 $μ$W. This allows us to obtain optical modulation with the low, millivolt-level signal generated by the SNSPD. Optical communication is becoming the preferred I/O solution in modern, room temperature high performance systems, and this work demonstrates its suitability for scalable cryogenic readout, which could help achieve the full potential of superconducting technologies.
We present an electro-optic modulator exploiting an array of Vanadium dioxide nanorods operating in the epsilon near regime as the active switching material integrated in a silicon waveguide. The modulator takes advantage of the insulator-to-metal transition of Vanadium dioxide to achieve a robust modulation depth of 19.7 dB/micron with a broad wavelength of operation. Using simulations, we demonstrate how the effective permittivity of the metamaterial can be tuned to a near-zero value by varying the nanorod geometry. The paper also proposes a novel hexagonal array design which achieves low in…
The realization of large-scale photonic circuit for quantum optics experiments at telecom wavelengths requires an increasing number of integrated detectors. Superconductive nanowire single photon detectors (SNSPDs) can be easily integrated on chip and they can efficiently detect the light propagating inside waveguides. The thermal budget of cryostats poses a limit on the maximum number of elements that can be integrated on the same chip due to the thermal impact of the readout electronics. In this paper, we propose and implement a novel scheme able for an efficient reading of several SNSPDs wi…
To better understand the origins of the timing resolution, also known as jitter, of superconducting nanowire single-photon detectors (SNSPDs), we have performed timing characterizations of a niobium nitride SNSPD with a dual-ended readout. By simultaneously measuring both readout pulses along with an optical timing reference signal, we are able to quantify each independent contribution to the total measured jitter. In particular, we are able to determine values for the jitter due to the stochastic nature of hotspot formation and the jitter due to the variation of the photon detection location …
A fundamental challenge of the quantum revolution is to efficiently interface the quantum computing systems operating at cryogenic temperatures with room temperature electronics and media for high data-rate communication. Current approaches to control and readout of such cryogenic computing systems use electrical cables, which prevent scalability due to their large size, heat conduction, and limited bandwidth1. A more viable approach is to use optical fibers which allow high-capacity transmission and thermal isolation. A key component in implementing photonic datalinks is a cryogenic optical m…
To analyze the switching dynamics and output performance of a superconducting nanowire single photon detector (SNSPD), the nanowire is usually modelled as an inductor in series with a time-varying resistor induced by absorption of a photon. Our recent experimental results show that, due to the effect of kinetic inductance, for a SNSPD made of a nanowire of sufficient length, its geometry length can be comparable to or even longer than the effective wavelength of frequencies contained in the output pulse. In other words, a superconducting nanowire can behave as a distributed transmission line s…
Superconducting nanowire single photon detectors (SNSPDs) are typically used as single-mode-fiber-coupled single-pixel detectors, but large area detectors are increasingly critical for applications ranging from microscopy to free-space quantum communications. Here, we explore changes in the rising edge of the readout pulse for large-area SNSPDs as a function of the bias current, optical spot size on the detector, and number of photons per pulse. We observe a bimodal distribution of rise times and show that the probability of a slow rise time increases in the limit of large spot sizes and small…
State-of-the-art Superconducting Nanowire Single Photon Detectors based on low-Tc materials reach 100% quantum efficiency. However, the response time is limited to >1-10 ns. Recently, it has been shown that due to a much lower kinetic inductance, a 100 ps response rate can be achieved in 120 $μ$m-long $MgB_{2}$ nanowires. In this work, we demonstrate experimentally that such $MgB_{2}$ nanowires function as single-photon detectors for both visible ($λ$= 630 nm) and infrared ($λ$= 1550 nm) photons when biased close to the critical current, with a dark count rate of <10 cps. $MgB_{2}$ photodetect…
Superconducting nanowire single-photon detectors (SNSPDs) are the highest performing photon-counting technology in the near-infrared (NIR). Due to delay-line effects, large area SNSPDs typically trade-off timing resolution and detection efficiency. Here, we introduce a detector design based on transmission line engineering and differential readout for device-level signal conditioning, enabling a high system detection efficiency and a low detector jitter, simultaneously. To make our differential detectors compatible with single-ended time taggers, we also engineer analog differential-to-single-…
Conventional readout of a superconducting nanowire single-photon detector (SNSPD) sets an upper bound on the output voltage to be the product of the bias current and the load impedance, $I_\mathrm{B}\times Z_\mathrm{load}$, where $Z_\mathrm{load}$ is limited to 50 $Ω$ in standard r.f. electronics. Here, we break this limit by interfacing the 50 $Ω$ load and the SNSPD using an integrated superconducting transmission line taper. The taper is a transformer that effectively loads the SNSPD with high impedance without latching. It increases the amplitude of the detector output while preserving the …
We investigate, both numerically and experimentally, the usefulness of a distributed nonlinearity in a passive coherent photonic reservoir computer. This computing system is based on a passive coherent optical fiber-ring cavity in which part of the nonlinearities are realized by the Kerr nonlinearity. Linear coherent reservoirs can solve difficult tasks but are aided by nonlinear components in their input or output layer. Here, we compare the impact of nonlinear transformations of information in the reservoir input layer, its bulk - the fiber-ring cavity - and its readout layer. For the inject…
By harnessing quantum superposition and entanglement, remarkable progress has sprouted over the past three decades from different areas of research in communication computation and simulation. To further improve the processing ability of microwave pho-tonics, here, we have demonstrated a quantum microwave photonic processing system using a low jitter superconducting nanowire single photon detector (SNSPD) and a time-correlated single-photon counting (TCSPC) module. This method uniquely combines extreme optical sensitivity, down to a single-photon level (below -100 dBm), and wide processing ban…
Encoding information onto optical fields is the backbone of modern telecommunication networks. Optical fibers offer low loss transport and vast bandwidth compared to electrical cables, and are currently also replacing coaxial cables for short-range communications. Optical fibers also exhibit significantly lower thermal conductivity, making optical interconnects attractive for interfacing with superconducting circuits and devices. Yet little is known about modulation at cryogenic temperatures. Here we demonstrate a proof-of-principle experiment, showing that currently employed Ti-doped LiNbO mo…
Adiabatic quantum-flux-parametron (AQFP) circuits can operate with extremely small energy dissipation (~1 zJ per junction at 5 GHz) and high sensitivity (~1 μA) owing to adiabatic switching. Thus, AQFP logic is suitable to use as readout interfaces for cryogenic detectors, such as superconducting nanowire single-photon detectors (SSPDs). In order to extend the application of AQFP logic to various detectors, it is crucial to achieve even better sensitivity because some detectors, such as WSi SSPDs and transition edge sensors (TESs), require sub-μA sensitivity. In the present study, we propose a…
Recent progress in the development of superconducting nanowire single-photon detectors (SNSPD) has delivered ex-cellent performance, and their increased adoption has had a great impact on a range of applications. One of the key characteristic of SNSPDs is their detection rate, which is typically higher than other types of free-running single-photondetectors. The maximum achievable rate is limited by the detector recovery time after a detection, which itself is linked to the superconducting material properties and to the geometry of the meandered SNSPD. Arrays of detectors biased individually c…
Characterization and Active Control of Position-Dependent Timing Dynamics in Superconducting Strip Single-Photon Detectors
NASA Jet Propulsion Laboratory, California Institute of Technology（美国国家航空航天局喷气推进实验室，加州理工学院）；Department of Applied Physics and Material Science, California Institute of Technology（加州理工学院应用物理与材料科学系）；National Institute of Standards and Technology（美国国家标准与技术研究院）；Department of Applied Physics Quantum Technologies, Université de Genève（日内瓦大学应用物理量子技术系）
