Fig. 1: Device and QP burst detection.

a Left: the optical image of the device with a bottom carrier chip and a top qubit chip containing 63 qubits and 105 couplers. The circuits on the half-transparent qubit chip are, on the back side, seen as a grid image, and color circles are added at the nodes to indicate qubits. 31 qubits in yellow are selected for measurement and 1 qubit in orange for QP injection. Right: Schematic of zoomed-in side view near a single qubit. (The sapphire carrier chip is in good thermal contact with the copper sample box on the periphery, here they are shown in direct contact under qubit area for simplicity). High-energy particles, such as muons (μ) and gamma-rays (γ), generate nonequilibrium phonons that break Cooper pairs thus causing QP bursts. Phonons can also be generated from the recombination of injected QPs. Two muon detectors, MDA and MDB, are located at the bottom of the copper sample box to detect muons that traverse through the device, sample box, and detectors. b Ramsey-based sequence for measuring the charge-parity state (violetred “e" for even state and gold “o" for odd state) of a qubit with the corresponding evolution of the qubit state on the Bloch sphere. c Sequence for measuring the charge-parity state using microwave control (XY), readout, and qubit frequency control (Z). The qubit frequency can be tuned to the idle point, readout point, reset point, and charge-sensitive point for qubit state control, measurement, initialization, and charge parity mapping, respectively. d Illustration of a typical QP burst. Charge-parity states of all selected qubits (Q₀ to Q_n) are continuously monitored with a period of 5.6 μs. The QP bursts induced by μ or γ are identified when there is a multiqubit simultaneous charge-parity jump (MQSCPJ).