High-Fidelity Qubit Transfer Between Leaky Memory Blocks

The transfer of qubits between memory blocks serves a central role in establishing a scalable quantum network. A reasonable quantum memory is built upon two coupled quantum field modes, namely, the transceiving mode (such as photons) suitable for propagating in connecting channels and the memory mode (such as phonons) for long-term qubit storage. It is crucial that the coupling between the two modes be dynamically controllable. Here, we consider the transfer of a single qubit from a source to a destination memory block, with the overall system consisting of 4 degrees of freedom. We employ the scattering-Lindbladian-Hamiltonian (SLH) formalism to model the open quantum system and derive the optimal temporal profile of the mode-coupling rate in each memory block for obtaining the maximum quantum-transfer-fidelity, particularly in the presence of intrinsic loss from each of the degrees of freedom. We show that, for the practical example of optomechanical memory blocks, the quantum-transfer-fidelity can reach as high as 96%, given practical resonator parameters.