The superconducting diode is a device that allows supercurrent to flow in one direction but not the other. Usually, the state that does not allow supercurrent has no Cooper pairs. Here we report a quantized version of the superconducting diode that operates solely between Cooper-paired states. This type of quantum superconducting diode takes advantage of quantized Shapiro steps for digitized output. The device consists of twisted high-temperature cuprate superconductors and exhibits the following characteristics. First, we show that a non-reciprocal diode behaviour can be initiated by training with current pulses without applying an external magnetic field. Then, we demonstrate perfect diode efficiency under microwave irradiation above liquid-nitrogen temperature. Lastly, the quantized nature of the output offers high resilience against input noise. These features open up opportunities to develop practical dissipationless quantum circuits.

Paper link: https://www.nature.com/articles/s41567-025-03098-y