Extended Data Fig. 3: Energy-relaxation times in the shielding experiment.

a, Energy relaxation times T₁ for qubits Q1–Q7 during the lead shield experiment while the shield is in up (blue) or down (orange) positions. b, The pulse sequence used to measure the energy-relaxation rate of all the qubits. First, a π-pulse is applied to all the qubits. After time t, a measurement pulse is used to determine the state of the qubits. The qubit excited-state population relaxes exponentially as a function of time. Blue circles show the measured qubit excited-state populations, and the orange line is an exponential fit using the model of equation (2). c, Stacked histogram of the combined energy-relaxation times for all of the qubits in the lead shield experiment. d, Plot of the noise power spectral density during the lead shield experiment for qubits Q3, Q4, Q6 and Q7. The red dashed line marks the rate of a single cycle of the lead shield. The green dashed line shows the estimated measurement period if all the data were gathered sequentially. Orange line is a fit to a power law, S = const/f^α, with α ≈ 1.5.