Abstract
We report on the spectrum of a superconducting transmon device coupled to a planar superconducting resonator in the strong dispersive limit where discrete peaks, each corresponding to a different number of photons, are resolved. A thermal population of 5.474 GHz photons at an effective resonator temperature of T = 120 mK results in a weak n = 1 photon peak along with the n = 0 photon peak in the qubit spectrum in the absence of a coherent drive on the resonator. Two-tone spectroscopy using independent coupler and probe tones reveals an Autler–Townes splitting in the thermal n = 1 photon peak. The observed effect is explained accurately using the four lowest levels of the dispersively dressed qubit–resonator system and compared to results from numerical simulations of the steady-state master equation for the coupled system.
Highlights
Over the past decade, superconducting quantum circuits have emerged as promising candidates for quantum computation [1, 2]
Many superconducting qubits are based on cavity [5, 9, 10] or circuit quantum electrodynamics [11, 12], which rely on the interaction of a qubit with the quantized electromagnetic field in a resonator
‘resonator-like’ transitions, taking into account higher order Kerr-type nonlinearities, only a few terms survive in the summation (4) and all others can be neglected in the rotating wave approximation (RWA)
Summary
Over the past decade, superconducting quantum circuits have emerged as promising candidates for quantum computation [1, 2]. Many superconducting qubits are based on cavity [5, 9, 10] or circuit quantum electrodynamics (cQED) [11, 12], which rely on the interaction of a qubit with the quantized electromagnetic field in a resonator. These architectures have been able to realize strong dispersive coupling between the qubit and resonator by using qubits with large dipole moments [5, 13]. While the Autler-Townes effect has previously been observed in superconducting qubits [18, 19], here the effect involves the dressed resonator-qubit states and is made possible by the strong dispersive coupling
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