Quantum repeater architecture using two-species trapped ions

Two co-trapped species of ions, one of which provides a long-lived quantum memory while the other serves as an optical communication qubit with high coupling efficiency, can be used as modules to construct nodes of a quantum repeater network. We propose a minimal architecture for the node design based on ion-trap modules with Yb ion as a memory qubit and Ba as the communication qubit. Our design includes quantum circuits that achieve intra-node Bell measurements between the ion-trap modules to perform entanglement-swapping locally within the nodes. Based on the fidelity of the required quantum operations and the currently available coupling efficiencies, we estimate the key generation rates that can be expected using the minimal architecture. We also analyze the dependence of the quantum key distribution rate on various experimental parameters, including coupling efficiency, gate infidelity, operation time and length of the elementary links.