An estimate of theta_14 independent of the reactor antineutrino flux determinations

In a previous paper [Phys. Rev. D 83, 113013 (2011)] we have shown that the solar sector data (solar and KamLAND) are sensitive to the parameter theta_14, encoding the admixture of the electron neutrino with a fourth (essentially) sterile mass eigenstate. In that work we evidenced that such data prefer a non-zero value of theta_14 and that such a preference is completely degenerate with that of non-zero theta_13. In this report we show how the evidence of theta_13 > 0, recently emerged from global neutrino data analyses, lifts such a degeneracy and disfavors the case of sterile neutrino mixing. By excluding from our analysis the total rate information coming from the reactor experiments we untie our results from any assumption on their flux normalization. In this way, we establish the robust upper bound sin^2 (theta_14) < 0.04 at the 90% C.L.Comment: 4 pages, 1 figure, minor changes, matches version accepted by PR

Decay and storage of multiparticle entangled states of atoms in collective thermostat

We derive a master equation describing the collective decay of two-level atoms inside a single mode cavity in the dispersive limit. By considering atomic decay in the collective thermostat, we found a decoherence-free subspace of the multiparticle entangled states of the W-like class. We present a scheme for writing and storing these states in collective thermostat

Quantum discord in spin-cluster materials

The total quantum correlation (discord) in Heisenberg dimers is expressed via the spin-spin correlation function, internal energy, specific heat or magnetic susceptibility. This allows one to indirectly measure the discord through neutron scattering, as well as calorimetric or magnetometric experiments. Using the available experimental data, we found the discord for a number of binuclear Heisenberg substances with both antiferro- and ferromagnetic interactions. For the dimerized antiferromagnet copper nitrate Cu(NO_3)_2*2.5H_2O, the three independent experimental methods named above lead to a discord of approximately 0.2-0.3 bit/dimer at a temperature of 4 K. We also determined the temperature behavior of discord for hydrated and anhydrous copper acetates, as well as for the ferromagnetic binuclear copper acetate complex [Cu_2L(OAc)]*6H_2O, where L is a ligand.Comment: 7 pages, 6 figure