Observation of Inter-Transition Interference

Toyofumi Ishikawa; Shumpei Masuda; Akiyoshi Tomonaga; Kosuke Mizuno; Kunihiro Inomata

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arXiv · 2611.07768

Observation of Inter-Transition Interference

Toyofumi Ishikawa·Shumpei Masuda·Akiyoshi Tomonaga·Kosuke Mizuno·Kunihiro Inomata

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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. By contrast, theoretical calculations that incorporate dissipative coupling between the corresponding transition coherences reproduce the essential features of the measured spectra. These results provide experimental evidence for ITI and demonstrate that dissipative coupling between transition coherences can qualitatively modify spectroscopic responses. More broadly, our work identifies transition coherences as a new arena for quantum interference in open quantum systems.

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Toyofumi Ishikawa, Shumpei Masuda, Akiyoshi Tomonaga, Kosuke Mizuno, Kunihiro Inomata. 2026-11-05. Observation of Inter-Transition Interference. https://arxiv.org/abs/2611.07768

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