Enhancing photon lifetime in coupled superconducting cavities through phase control

Three-dimensional superconducting cavities with high quality factors have found extensive applications in high-energy physics, quantum information science, sensing, and so on. Here we present our study of the photon lifetime of two co-resonant superconducting cavities coupled by a coaxial cable with a tunable phase parameter. We find that both the phase accumulation on the cable and the phases of initial states affect the lifetime of photons in each cavity as a result of the interference between cavity fields. Our experimental study via ring down measurement at a cryogenic condition observed a factor of two enhancement of cavity photon lifetime by optimizing the resonance frequency matching and the phase parameter. We envision that the coupled superconducting cavities can be exploited for enhancing the performance of three-dimensional quantum memory and quantum information processors.