Centre-of-mass motion-induced decoherence and entanglement generation in a hybrid quantum repeater

Quantum communication over long distances relies on the ability to create entanglement between two remote quantum nodes. Recent proposals aiming at experimental realization propose a hybrid quantum repeater setup where two distant material qubits are entangled by light–matter interaction. Motivated by these developments, we investigate possible decoherence effects originating from the centre-of-mass motion of the spatially well-separated trapped qubits. Within the Lamb–Dicke regime we use photon exchange involving coherent states of the radiation field to entangle the two material qubits. Optimal generalized photonic field measurements are used to achieve entangled qubit pairs with high fidelities and high success probabilities. We demonstrate that the quality of the achievable two-qubit entanglement crucially depends on the trap frequencies involved. Furthermore, dynamical decoupling schemes are proposed which are capable of suppressing centre-of-mass motion-induced decoherence effects significantly and which involve only local operations acting on the spatially well-separated material qubits. (paper)