Unexpectedly Allowed Transition in Two Inductively Coupled Transmons

We present experimental results in which the unexpected zero-two transition of a circuit composed of two inductively coupled transmons is observed. This transition shows an unusual magnetic flux dependence with a clear disappearance at zero magnetic flux. In a transmon qubit, the symmetry of the wave functions prevents this transition to occur due to selection rule. In our circuit, the Josephson e...