Time-Resolved Quantum Process Tomography of a Compact 3D Quantum Memory

Storing a photonic state in a 3D superconducting cavity as long as possible and reading out its information as fast as possible is a challenging task due to the conflicting requirements regarding the coupling strength between the cavity and readout circuit. This problem can be solved by a multimode compact 3D memory scheme employing a wealky and strongly coupled storage and readout mode with both coupled to a transmon qubit [Xie et al., Appl. Phys. Lett. 112, 202601 (2018)]. However, comparing the experimental data of the time evolution of the quantum process tomography with an empirical simulation, we saw difference in the relaxation behavior become obvious. To clarify this issue we perform an ab initio quantum simulations. In particular, these simulations allow us to understand yet unknown physics behind the compact 3D memory design and improve the protocol for the quantum memory process.