Tunable compact on-chip superconducting switch

We develop a compact four-port superconducting switch with tunable operating frequency in the range from 4.8 to 7.3 GHz. Isolation between channels exceeds 20 dB over a bandwidth of several hundred megahertz, exceeding 40 dB at some frequencies. The footprint of the device is $80\times 420\text{μ}{m}^2$. The tunability requires only a global flux bias without either permanent magnets or microelectromechanical structures. As the switch is superconducting, the heat dissipation during operation is negligible. The device can operate at up to $-80\mathrm{dBm}$, which corresponds to $2.5\times {10}^6$ photons per microsecond at a frequency of 6 GHz. The device shows the possibility to be operated as a beam splitter with tunable splitting ratio.