Observation of Inter-Transition Interference

arXiv:2611.07768v1 Announce Type: new Abstract: Many well-known quantum interference phenomena are associated with coherent superpositions of quantum states. Recent theoretical work showed that dissipative coupling between transition coherences can give rise to a distinct form of quantum interference in open quantum systems, termed inter-transition interference (ITI). Here we experimentally observe ITI through coherent microwave reflection spectroscopy of a superconducting artificial atom realized by a Kerr parametric oscillator. Using strong parametric driving, we access a regime in which two transitions become nearly degenerate and simultaneously contribute to the reflected response. The observed spectral lineshapes are not adequately captured by a model of independent transitions.