Observation of a collective mode of an array of transmon qubits
Kirill Shulga, P. Yang, Gleb Fedorov, M. V. Fistul, Martin P. Weides, Alexey Vladimirovich Ustinov · Journal of Experimental and Theoretical Physics Letters · 2017
Arrays of transmon qubits coupled to a λ/2 superconducting coplanar waveguide resonator have been studied by microwave spectroscopy. The emergence of a collective mode has been discovered for a cluster of N > 5 qubits, whose coupling constant to the electromagnetic field in the resonator is √N times greater compared to a single qubit. In addition, the emergence of collective multiphoton transitions exciting higher levels of a qubit cluster has been demonstrated and the interaction of an individual qubit with such a cluster has been investigated.