Quantum storage and information transfer with superconducting qubits

We design theoretically a new device to realize the general quantum storage based on dcSQUID charge qubits. The distinct advantages of our scheme are analyzed in comparison with existing storage scenarios. More arrestingly, the controllable XY-model spin interaction has been realized for the first time in superconducting qubits, which may have more potential applications besides those in quantum information processing. The experimental feasibility is also elaborated.Comment: 4 pages, 2 figure

Fast entanglement of two charge-phase qubits through nonadiabatic coupling to a large junction

We propose a theoretical protocol for quantum logic gates between two Josephson junction charge-phase qubits through the control of their coupling to a large junction. In the low excitation limit of the large junction when $E_{J}\gg E_{c}$, it behaves effectively as a quantum data-bus mode of a harmonic oscillator. Our protocol is efficient and fast. In addition, it does not require the data-bus to stay adiabatically in its ground state, as such it can be implemented over a wide parameter regime independent of the data-bus quantum state.Comment: 5 pages, 1 figur

SU(m|n) supersymmetric Calogero-Sutherland model confined in harmonic potential

In this work, we study a continuous quantum system of a mixture of bosons and fermions with the supersymmetry SU(m|n). The particles are confined in a harmonic well and interact with each other through the 1/r2 interaction. The ground state wavefunction is constructed explicitly for the most general SU(m|n) case, with the ground state energy given explicitly. The full energy spectrum of excitations in the SU(m|n) model is also equal spaced. In the limiting case where there are no bosons in the system, our results reduce to those obtained previously.Comment: 9 pages, preprint of ETH-Lausanne (August 1996

Parity-locking effect in a strongly-correlated ring

Orbital magnetism in an integrable model of a multichannel ring with long-ranged electron-electron interactions is investigated. In a noninteracting multichannel system, the response to an external magnetic flux is the sum of many diamagnetic and paramagnetic contributions, but we find that for sufficiently strong correlations, the contributions of all channels add constructively, leading to a parity (diamagnetic or paramagnetic) which depends only on the total number of electrons. Numerical results confirm that this parity-locking effect is robust with respect to subband mixing due to disorder.Comment: part of lecture presented in the conference ``Unconventional quantum liquids", appearing in Z. Phy