Observing quantum non-locality in the entanglement between modes of massive particles

We consider the question of whether it is possible to use the entanglement between spatially separated modes of massive particles to observe nonlocal quantum correlations. Mode entanglement can be obtained using a single particle, indicating that it requires careful consideration before concluding whether experimental observation, e.g. violation of Bell inequalities, is possible or not. In the simplest setups analogous to optics experiments, that observation is prohibited by fundamental conservation laws. However, we show that using auxiliary particles, mode entanglement can be converted into forms that allow the observation of quantum non-locality. The probability of successful conversion depends on the nature and number of auxiliary particles used. In particular, we find that an auxiliary Bose-Einstein condensate allows the conversion arbitrarily many times with a small error that depends only on the initial state of the condensate.Comment: 8 pages (two-column), 2 figure

Cooling a magnetic resonance force microscope via the dynamical back-action of nuclear spins

We analyze the back-action influence of nuclear spins on the motion of the cantilever of a magnetic force resonance microscope. We calculate the contribution of nuclear spins to the damping and frequency shift of the cantilever. We show that, at the Rabi frequency, the energy exchange between the cantilever and the spin system cools or heats the cantilever depending on the sign of the high-frequency detuning. We also show that the spin noise leads to a significant damping of the cantilever motion.Comment: 15 pqges, 11 figures. The last part of Section IV.A and Section IV B were rewritten. We added three new graphs: Figs. 5, 7, 9 and all graphs in this subsection were recalculated for T=600 mK as in the experiment. Several new references were adde

Hybridized solid-state qubit in the charge-flux regime

Most superconducting qubits operate in a regime dominated by either the electrical charge or the magnetic flux. Here we study an intermediate case: a hybridized charge-flux qubit with a third Josephson junction (JJ) added into the SQUID loop of the Cooper-pair box. This additional JJ allows the optimal design of a low-decoherence qubit. Both charge and flux $1/f$ noises are considered. Moreover, we show that an efficient quantum measurement of either the current or the charge can be achieved by using different area sizes for the third JJ.Comment: 7 pages, 5 figures. Phys. Rev. B, in pres