Scalable Optical Control of Persistent Current Switches for Quantum Circuits

Quantum circuits with thousands of tunable parameters can use persistent current switches, reducing complexity compared to individual bias lines. We demonstrate the use of a cryogenic laser scanner with a MEMS mirror (<300 nW dissipation) inside a light-tight sample box to control 6 persistent currents with a single bias line. Focused optical pulses (~1 µs, 40 µm spot size) drive selected superconducting segments normal, enabling current trapping without dedicated heaters or additional cryogenic wiring. Thermal modeling predicts that standard Al traces may be switched with ~ 5 µW incident laser power at repetition rates approaching 5 MHz. We present scaling arguments suggesting that a similar system could address 60,000 currents in a 20 mm x 20 mm area with minimal demands on the circuit layout, addressing all switches in one second. Furthermore, this versatile laser scanning system provides a tool for localized energy deposition, enabling in-situ studies of device response or manipulation of trapped flux within the same platform.