Ballistic quantum information transfer and effective entangling gate through homogeneous quantum wires

Effective quantum-state and entanglement transfer can be obtained by inducing a coherent dynamics in quantum wires with homogeneous intrawire interactions [1,2]. This goal is accomplished by optimally tuning the coupling between the wire endpoints and the two qubits there attached. A general procedure to determine such value is devised, and scaling laws between the optimal coupling and the length of the wire are found. The procedure is implemented in the case of a wire consisting of a spin-1/2 XY chain: results for the time dependence of the quantities which characterize quantum-state and entanglement transfer are found of extremely good quality also for very long wires. The present approach neither requires engineered intrawire interactions nor a specific initial pulse shaping, and can be applied to any quantum channels interacting through a quasi-free Hamiltonian, i.e. an Hamiltonian that can be cast into a quadratic form in terms of some creation and annihilation operator. Thanks to the above optimization procedure, the transmission quality is not substantially affected by the initial state of the wire. However, in general without optimization and with more complex interacting Hamiltonians, the transmission strongly depends also on the initial state, which hence has to be engineered [3].