Narrow muon bundles from muon pair production in rock

We revise the process of muon pair production by high-energy muons in rock using the recently published cross-section. The three-dimensional Monte Carlo code MUSIC has been used to obtain the characteristics of the muon bundles initiated via this process. We have compared them with those of conventional muon bundles initiated in the atmosphere and shown that large underground detectors, capable of collecting hundreds of thousands of multiple muon events, can discriminate statistically muon induced bundles from conventional ones. However, we find that the enhancement of the measured muon decoherence function over that predicted at small distances, recently reported by the MACRO experiment, cannot be explained by the effect of muon pair production alone, unless its cross-section is underestimated by a factor of 3.Comment: 10 pages, 1 table, 2 figures, to be published in Physics Letters

Nonlinear dissipation can combat linear loss

We demonstrate that it is possible to compensate for effects of strong linear loss when generating non-classical states by engineered nonlinear dissipation. We show that it is always possible to construct such a loss-resistant dissipative gadget in which, for a certain class of initial states, the desired non-classical pure state can be attained within a particular time interval with an arbitrary precision. Further we demonstrate that an arbitrarily large linear loss can still be compensated by a sufficiently strong coherent or even thermal driving, thus attaining a strongly non-classical (in particular, sub-Poissonian) stationary mixed states.Comment: Submitted to PR

Composite Cluster States and Alternative Architectures for One- Way Quantum Computation

We propose a new architecture for the measurement-based quantum computation model. The new design relies on small composite light-atom primary clusters. These are then assembled into cluster arrays using ancillary light modes and the actual computation is run on such a cellular cluster. We show how to create the primary clusters, which are Gaussian cluster states composed of both light and atomic modes. These are entangled via QND interactions and beamsplitters and the scheme is well described within the continuous-variable covariance matrix formalism.Comment: arXiv admin note: text overlap with arXiv:1007.040

Nonclassical states of the second optical harmonic in the presence of self-action

The quantum theory of coherent radiation frequency doubling in crystals with quadratic and cubic optical nonlinearities is developed. The possibility of producing the quadrature-squeezed state of the second harmonic (SH) field is shown. The nonclassical SH states arise due to self-action effect