A superconducting electronic signal output circuit includes a signal source section configured to provide a voltage and/or current signal. The signal source section comprises a superconducting nanowire single photon detector, SNSPD, a switchable output section connected to the signal source section and having a first superconducting switch configured to selectably cause the signal to be output to an output of the superconducting electronic signal output circuit, and a switchable sink section connected to the signal source section and the switchable output section and having a second superconducting switch configured to selectably cause the signal to be directed to a reference potential.