Leonardo Banchi - Università di Firenze #
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].
The proposed scheme is not only suitable for transmitting states from one wire endpoint to the other one, but it
can also be used for exchanging information between the endpoints contemporaneously. In particular, in Ref.
[4] we show that the optimal dynamics described in the previous section generates an effective entangling gate
between the distant endpoints, and permits hence to create long-distance entanglement.
References
[1] L. Banchi, T. J. G. Apollaro, A. Cuccoli, R. Vaia, P. Verrucchi, Phys. Rev. A 82, 052321, (2010).
[2] L. Banchi, T. J. G. Apollaro, A. Cuccoli, R. Vaia, P. Verrucchi, arXiv:1105.6058
[3] A. Bayat, L. Banchi, S. Bose, P. Verrucchi, arXiv:1104.0718
[4] L. Banchi, A. Bayat, P. Verrucchi, S. Bose, Phys. Rev. Lett. 106, 140501, (2011)