Collapse and revival of the Transmon potential under parametric coupling to a strongly driven resonator
M.A. Morssink (TU Delft - Applied Sciences)
M. Villiers – Mentor (TU Delft - Applied Sciences)
G.A. Steele – Mentor (TU Delft - Applied Sciences)
C.K. Andersen – Graduation committee member (TU Delft - QRD/Andersen Lab)
A.R. Akhmerov – Graduation committee member (TU Delft - Applied Sciences)
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Abstract
The recent quest for large resonator photon numbers in circuit quantum electrodynamics (cQED) has led to the discovery of ionization in Transmon-resonator systems. Ionization compromises the quantum non-demolition nature of Transmon readout. Furthermore, it can lead to dephasing in elements coupled to the Transmon, which is detrimental to optomechanical schemes using an auxiliary qubit to create quantum states. Since the transverse nature of the usual dipolar capacitive coupling lies at the origin of ionization, our team engineered a new parametric coupling scheme that can potentially suppress ionization by being inherently more longitudinal.
Using a large detuning in combination with parameters chosen based on branch analysis, ionization in the system was largely suppressed. This suppression enabled the observation of the collapse and revival of the Transmon potential under parametric coupling at high resonator photon numbers. The measured Transmon Stark shift indicates a collapse of the potential at 12,300 photons and a subsequent revival, in agreement with the derived theoretical model. Resonator phase-space measurements further confirmed the collapse and revival. The newly identified revived regime potentially enables coherent Transmon operation at high photon numbers.