Concept 22 of 42 · Circuit QED and Decoherence

Qubit relaxation T1

Energy decay transfers qubit excitation into environmental degrees of freedom.

01 / Mathematical framework
$$P_e(t)=P_e(0)e^{-t/T_1}$$

Physical intuition

Energy decay transfers qubit excitation into environmental degrees of freedom. This is the starting point for understanding how superconducting circuit parameters determine quantum energy levels and dynamics.

Deep dive: how the mechanism works

Dielectric loss, radiation, Purcell decay and quasiparticles can absorb qubit energy.

How the quantum phenomenon appears

A prepare-wait-measure sequence extracts energy relaxation time. To establish the predicted quantum behavior, connect the circuit Hamiltonian to a measured transition, coherence experiment, gate benchmark or calibrated readout signal.

Assumptions and limitations

Multi-exponential decay or leakage may invalidate a single T1 model.

Research and simulation exercise

Identify the tunable parameters, predict the observable from the stated model, and sweep one parameter while holding the others fixed. Compare against a simpler reference model, quantify loss and uncertainty, and state which observations would falsify the hypothesis.

Connect the ideas

See the chapter guide and further reading.

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