An ultrahigh-impedance superconducting thermal switch for interfacing superconductors to semiconductors and optoelectronics

The ability to interface superconductors with semiconductors is a critically-missing component of the advanced computing ecosystem. At present, a significant number of scalable quantum computing and neuromorphic architectures plan to operate at cryogenic temperatures, using superconductors as the basis of their architecture or as a measurement component. In these architectures, semiconductor systems are often proposed as a top-level control with low-temperature passive components and intermediary superconducting electronics acting as the direct interface to the lowest-temperature stages--this stratification is required because semiconductor-based amplification of small superconducting signals consumes too much power for extensive use at kelvin-scale temperatures. As a result, these architectures necessarily require a low-power superconductor-semiconductor interface that presently does not exist, for example to leverage CMOS coprocessors for classical control of superconducting qubits, or as a means to drive optoelectronics from superconducting detectors. Here we present a superconducting switch device that is capable of translating low-voltage superconducting inputs directly into semiconductor-compatible (>1,000 mV) outputs at kelvin-scale temperatures. As a demonstration of a superconductor-semiconductor interface, we have used the switch to drive an LED in a photonic integrated circuit, generating photons at 1 K from a low-voltage input and detecting them with an on-chip superconducting single-photon detector. We additionally characterized the device's timing response ( 1 M{\Omega}), and energy requirements (0.18 fJ/um^2, 3.24 mV/nW). Despite its simplicity as a thermal device, we found that this device is an extremely promising candidate for a superconductor-to-semiconductor logical interface.