Drive-induced dephasing in circuit QED*

The transmon succeeded the Cooper-pair box by trading a smaller anharmonicity for an exponential reduction of the sensitivity to charge noise. Despite this reduction, a number of experiments show that strongly driving the transmon leads to a decrease in T2. As numerous qubit manipulation schemes rely on the use of strong drives, it urges the need for understanding the sources of this decrease.

Here, we show that the band structure of the transmon is modified in the presence of the drives, yielding a global enhancement of the dephasing rate.