Department of Physics & Astronomy
University of New Mexico

CQuIC Seminars

Dynamics of transmon ionization

Presented by Alexandre Blais, Sherbrooke

Quantum computers have the potential to efficiently solve complex problems but the realization of such devices remains a formidable task. Superconducting quantum circuits, and in particular circuit QED with transmon qubits, has been used to realize small quantum processors with over 100 qubits. Qubit readout in this architecture has been experimentally demonstrated with an accuracy approaching 99% in less than 100 ns. While impressive, this is far from enough to build robust quantum computers, and attempts to achieve higher accuracy have been unsuccessful. Indeed, increasing the amplitude of the measurement tone, which should in principle improve the readout fidelity, results in unwanted qubit transitions and in a drop of the readout fidelity. After a review of the basic operating principle of the transmon qubit, I will report simulation of the qubit dynamics under measurement. These simulations highlight parameter regimes where the measurement tones causes spurious qubit transitions to highly excited states, akin to the ionization of an atom. Comparison to experimental data suggests that these results can be used to optimize device parameters to improve qubit readout in future generation of circuit QED devices.

3:30 pm, Thursday, May 5, 2022

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