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Magnetic Qubits as Hardware for Quantum Computers
Tejada, J.; Chudnovsky, E.M.; del Barco, E.; Hernandez, J.M.; Spiller, T.P.
Keyword(s): quantum computing; magnetic clusters; magnetic particles; qubits
Abstract: Please Note. This abstract contains mathematical formulae which cannot be represented here. We propose two potential realisations for quantum bits based on nanometre scale magnetic particles of large spin S and high anisotropy molecular clusters. In case (1) the bit-value basis states *n and *n are the ground and first excited spin states Sz = S and S-1, separated by an energy gap given by the ferromagnetic resonance (FMR) frequency. In case (2), when there is significant tunnelling through the anisotropy barrier, the qubit states correspond to the symmetric, *n, and antisymmetric, *n, combinations of the two-fold degenerate ground state Sz = * S. In each case the temperature of operation must be low compared to the energy gap, D, between the states *n and *n. The gap D in case (2) can be controlled with an external magnetic field perpendicular to the easy axis of the molecular cluster. The states of different molecular clusters and magnetic particles may be entangled by connecting them by superconducting lines with Josephson switches, leading to the potential for quantum computing hardware. Notes: J. Tejada, E. del Barco and J.M. Hernandez, Physics Department, University of Barcelona, Diagonal 647, 08028 Barcelona, Spain. E.M. Chudnovsky, Lehman College of the City University of New York, Bedford Park Boulevard West, NY 10468-1589.
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