  Due to stringent thermal budgets in cryogenic technologies such as
superconducting quantum computers and sensors, minimizing the energy
dissipation and power consumption of cryogenic electronic components is pivotal
for large-scale devices. However, electronic building blocks that
simultaneously offer low energy consumption, fast switching, low error rates, a
small footprint and simple fabrication remain elusive. In this work, we
demonstrate a superconducting switch with attojoule switching energy, high
speed (pico-second rise/fall times), and high integration density (on the order
of $10^{-2}$ $\mathrm{\mu m^2}$ per switch). The switch consists of a
superconducting channel and a metal heater separated by an insulating silica
layer, prepared using lift-off techniques. We experimentally demonstrate
digital gate operations utilizing this technology, such as NOT, NAND, NOR, AND,
and OR gates, with a few femtojoule energy consumption and ultralow bit error
rates < $10^{-8}$. In addition, we build volatile memory elements with few
femtojoule energy consumption per operation, a nanosecond operation speed, and
a retention time over $10^5$ s. These superconducting switches open new
possibilities for increasing the size and complexity of modern cryogenic
technologies.
