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Superconducting optoelectronic single-photon synapses


Superconducting optoelectronic hardware could be used to create large-scale and computationally powerful artificial spiking neural networks. The approach combines integrated photonic components that offer few-photon, light-speed communication with superconducting circuits that offer fast, energy-efficient computation. However, the monolithic integration of photonic and superconducting devices is needed to scale this technology. Here we report superconducting optoelectronic synapses that are created by monolithically integrating superconducting nanowire single-photon detectors with Josephson junctions. The circuits perform analogue weighting and the temporal leaky integration of single-photon presynaptic signals. Synaptic weighting is implemented in the electronic domain allowing binary, single-photon communication to be maintained. Records of recent synaptic activity are locally stored as current in superconducting loops, and dendritic and neuronal nonlinearities are implemented with a second stage of Josephson circuitry. This hardware offers synaptic time constants spanning four orders of magnitude (hundreds of nanoseconds to milliseconds). The synapses are responsive to presynaptic spike rates exceeding 10 MHz and consume approximately 33 aJ of dynamic power per synapse event before accounting for cooling. This demonstration also introduces new avenues for realizing large-scale single-photon detector arrays.

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Fig. 1: Synapse concept.
Fig. 2: Layouts and completed circuits.
Fig. 3: Detailed characterization of 6.25 μs, 2.5 μH synapse.
Fig. 4: Comparison of synapses with varying time constants.
Fig. 5: Heat maps of synaptic response.
Fig. 6: The 5 ms synapse operating in the number-counting regime.

Data availability

The data that support the findings of this study are publicly available via Figshare at


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We appreciate the recommendations on the read-out SQUID design from B. Mates, M. Durkin and J. Aumentado. We appreciate insights on the experimental characterization from M. Castellanos-Beltran and D. Rampini. This work was made possible by the institutional support from the National Institute of Standards and Technology (award no. 70NANB18H006; B.A.P.) and the effort to advance hardware for artificial intelligence and by the DARPA Invisible Headlights Program (HR0011149863 and HR0011151332; S.K. and J.M.S.).

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Authors and Affiliations



S.K. contributed to the design of experiment, circuit concepts, circuit modelling, layout, fabrication, experimental apparatus and experimental characterization. B.A.P. contributed to the circuit modelling, experimental apparatus, experimental characterization and data analysis. J.C. contributed to the fabrication and experimental characterization. A.N.M. contributed to the circuit concepts and experimental characterization. S.M.B. contributed to the circuit concepts and experimental apparatus. A.N.T. contributed to the circuit concepts and experimental apparatus. A.L., J.B., A.F. and D.O. contributed to the fabrication process development. R.P.M. contributed to the project management. S.W.N. contributed to the project management and experimental characterization. J.M.S. contributed to the experiment design, circuit concepts, circuit modelling, layout, fabrication, data analysis and project management. All the authors contributed to the manuscript preparation.

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Correspondence to Jeffrey M. Shainline.

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Nature Electronics thanks Robert Dynes, Robert Hadfield and Taro Yamashita for their contribution to the peer review of this work.

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Khan, S., Primavera, B.A., Chiles, J. et al. Superconducting optoelectronic single-photon synapses. Nat Electron 5, 650–659 (2022).

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