(1) sensitivity to magnetic fields, (2) limited gain, (3) inability to drive large impedances, and (4) difficulty in controlling the junction critical current (which depends sensitively on subAngstrom-scale thickness variation of the tunneling barrier). Here we present a nanowire-based superconducting electronic device, which we call the nanocryotron (nTron) 3 , that does not rely on Josephson junctions and can be patterned from a single thin film of superconducting material with conventional electron-beam lithography. The nTron is a 3-terminal, "T"-shaped planar device with a gain of ~20 that is capable of driving impedances of more than 100 kΩ, and operates in typical ambient magnetic fields at temperatures of 4.2K. The device uses a localized, Joule-heated hotspot 4,5,6 formed in the gate to modulate current flow in a perpendicular superconducting channel. We have characterized the nTron, matched it to a theoretical framework, and applied it both as a digital logic element in a half-adder circuit, and as a digital amplifier for superconducting nanowire single-photon detectors pulses. The nTron has immediate applications in classical and quantum communications, photon sensing and

Detecting spatial and temporal information of individual photons by using singlephoton-detector (SPD) arrays is critical to applications in spectroscopy, communication, biological imaging, astronomical observation, and quantum-information processing. Among the current SPDs 1 , detectors based on superconducting nanowires have outstanding performance 2 , but are limited in their ability to be integrated into large scale arrays due to the engineering difficulty of high-bandwidth cryogenic electronic readout [3][4][5][6][7][8] . Here, we address this problem by demonstrating a scalable single-photon imager using a single continuous photon-sensitive superconducting nanowire microwave-plasmon transmission line. By appropriately designing the nanowire's local electromagnetic environment so that the nanowire guides microwave plasmons, the propagating voltages signals generated by a photon-detection event were slowed down to ~ 2% of the speed of light. As a result, the time difference between arrivals of the signals at the two 2 ends of the nanowire naturally encoded the position and time of absorption of the photon. Thus, with only two readout lines, we demonstrated that a 19.7-mm-long nanowire meandered across an area of 286 μm × 193 μm was capable of resolving ~ 590 effective pixels while simultaneously recording the arrival times of photons with a temporal resolution of 50 ps. The nanowire imager presents a scalable approach to realizing high-resolution photon imaging in time and space. Main Text:Quantum and classical optics are currently limited by our ability to efficiently sense and process information about single photons. For example, to enhance the information-carrying capacity of a quantum channel 9 and improve security in quantum key distribution 10,11 , information is typically encoded in the position and arrival time of individual photons.Determining the spatial and temporal information of photons is currently accomplished by single-photon detector (SPD) arrays. Among existing SPD array technologies, the transition edge sensor (TES) and the microwave kinetic inductance detector (MKID) provide moderate spectral information but less impressive temporal resolution (e.g., the timing jitter is measured in nanoseconds for TESs 12 and microseconds for MKIDs 13 ). Photomultiplier tubes and singlephoton avalanche diodes have sub-1-ns timing jitter in the visible domain, but their detection performance deteriorates in the infrared, and scaling these technologies to large spatial arrays is challenging 1 . Improved timing performance of sub-20-ps timing jitter 14 and sub-10-ns recovery time 15 is possible with superconducting-nanowire single-photon detectors (SNSPDs), which also have been demonstrated to have near-unity detection efficiency 2 , less than 1 dark-count per second (cps) 16 , a wide spectral response from the visible to infrared 17 and greater than 100 cps 3 counting rate 18 . However, attempts to create arrays of SNSPDs have had limited success 3-8 .Traditional row-column rectangular pixel arra...

Thin superconducting films form a unique platform for geometrically confined, strongly interacting electrons. They allow an inherent competition between disorder and superconductivity, which in turn enables the intriguing superconducting-to-insulating transition and is believed to facilitate the comprehension of high-T c superconductivity. Furthermore, understanding thin film superconductivity is technologically essential, e.g., for photodetectors and quantum computers. Consequently, the absence of established universal relationships between critical temperature (T c ), film thickness (d), and sheet resistance (R s ) hinders both our understanding of the onset of the superconductivity and the development of miniaturized superconducting devices. We report that in thin films, superconductivity scales as dT c (R s ). We demonstrated this scaling by analyzing the data published over the past 46 years for different materials (and facilitated this database for further analysis). Moreover, we experimentally confirmed the discovered scaling for NbN films, quantified it with a power law, explored its possible origin, and demonstrated its usefulness for nanometer-length-scale superconducting film-based devices. Relationships between low-temperature and normal-state properties are crucial for understanding superconductivity. For instance, the Bardeen-Cooper-Schrieffer theory (BCS) successfully associates the normal-to-superconducting transition temperature, T c , with material parameters, such as the Debye temperature ( D ) and the density of states at the Fermi level [N (0)]. Hence, the BCS model allows us to infer superconducting characteristics (i.e., T c ) from properties measured at higher temperatures [1]. In the BCS framework, superconductivity occurs when attractive phonon-mediated electron-electron interactions overcome the Coulomb repulsion, giving rise to paired electrons (Cooper pairs) with a binding energy gap:. Moreover, within a superconductor, all Cooper pairs are coupled, giving rise to a collective electron interaction. Such a collective state is described by a complex global order parameter with real amplitude ( ) and phase (ϕ): = e iϕ .Because superconductivity relies on a collective electron behavior, the onset of superconductivity occurs when the number of participating electrons is just enough to be considered collective, i.e., at the nanoscale [2-5]. Thus, it is known that the superconductivity-disorder interplay varies in thin films and is effectively tuned with the film thickness (d) or with the disorder in the system, which is represented by sheet resistance of the film at the normal state (R s ) [6][7][8][9][10]. The mechanism of superconductivity in thin films has been investigated since the 1930s [6] increase in T c with decreasing thickness in aluminum films in a study that pioneered the currently ongoing research of thin superconducting films. This enhancement of T c , which is still not completely understood, was later confirmed by Strongin et al. [12], who also reported the more common be...

Circuits using superconducting single-photon detectors and Josephson junctions to perform signal reception, synaptic weighting, and integration are investigated. The circuits convert photondetection events into flux quanta, the number of which is determined by the synaptic weight. The current from many synaptic connections is inductively coupled to a superconducting loop that implements the neuronal threshold operation. Designs are presented for synapses and neurons that perform integration as well as detect coincidence events for temporal coding. Both excitatory and inhibitory connections are demonstrated. It is shown that a neuron with a single integration loop can receive input from 1000 such synaptic connections, and neurons of similar design could employ many loops for dendritic processing.

We demonstrate cryogenic, electrically-injected, waveguide-coupled Si light-emitting diodes (LEDs) operating at 1.22 µm. The active region of the LED consists of W centers implanted in the intrinsic region of a p-in diode. The LEDs are integrated on waveguides with superconducting nanowire single-photon detectors (SNSPDs). We demonstrate the scalability of this platform with an LED coupled to eleven SNSPDs in a single integrated photonic device. Such on-chip optical links may be useful for quantum information or neuromorphic computing applications.