Figure 4. Matrix elements calculation.

Driven resonator transitions |1, −〉 ↔ |2, +〉 (a) and |1, −〉 ↔ |2, −〉 (b). (c,d) correspond to the same transitions as in (a,b) for the case of single-qubit driving. Equation (16) is numerically solved (solid line) and compared to the Bloch-Siegert (BS) Hamiltonian Equations (7), (8), (11) and (12) (dashed line) and the Jaynes-Cummings (JC) Hamiltonian (dash-dotted line). (e) Relative weight T_{|1−〉↔|2−〉}/T_{|1−〉↔|2+〉} of the matrix elements calculated in (a–d) for resonator (solid blue) and qubit (dashed green) driving. The value decays due to the increased similarity between the structure of the eigenstates when approaching the deep strong coupling regime¹,²⁷. The vertical dashed lines mark the operating conditions of the current experiment.