Ziyi Zhao of JILA, National Institute of Standards and Technology and the University of Colorado, Boulder, and colleagues have designed a new superconducting switch capable of handling more than 100 pW of readout power, a crucial step toward scaling quantum processors. The switch utilizes a stable persistent current associated with tens of flux quanta, minimizing the need for constant recalibration and reducing static power consumption. This design addresses a key limitation in current quantum systems by employing direct current actuation, which reduces potential crosstalk between densely integrated qubits and facilitates more modular cryogenic measurements. The work demonstrates a switch with over 20 dB isolation, comparable to commercial ferrite isolators, and a modulation bandwidth broader than 600 MHz. Persistent Current Bias Enables Long-lived Switch States Researchers have designed a new microwave switch that minimizes energy consumption and signal interference, addressing critical limitations in current quantum systems. The design centers around a persistent current bias and direct current actuation, a departure from conventional methods that depend on continuous magnetic flux biasing and dynamic flux actuation. These traditional approaches often struggle with isolating control signals, creating crosstalk that limits the density of integrated switches and other sensitive components. The new switch circumvents this issue by trapping a current within the superconducting loop, maintaining a stable state for extended periods. Measurements reveal the persistent current remains consistent for less than 1% decay per day, a characteristic crucial for reliable operation in complex quantum circuits. This stability is achieved through a carefully engineered inductive Wheatstone bridge, incorporating 20 tunable inductors, each an antisymmetric rf-SQUID, to implement the necessary inductance. Beyond stability, the switch demonstrates performance metrics suitable for advanced quantum information processing. Transmission measurements show greater than 20 dB of isolation in the off state, a level comparable to commercially available ferrite isolators. This high