S. Shelly Sharma

Double-beta decay in pn-QRPA model with isospin and SU(4) symmetry constraints

The transition matrix elements for the 0+ → 0+ double-beta decays are calculated for 48Ca, 76Ge, 82Se, 100Mo, 128Te and 130Te nuclei, using a δ-interaction. As a guide, to fix the particle-particle interaction strengths, we exploit the fact that the missing symmetries of the mean-field approximation are restored in the random phase approximation by the residual interaction. Thus, the T = 1, S = 0 and T = 0, S = 1 coupling strengths have been estimated by invoking the partial restoration of the isospin and Wigner SU(4) symmetries, respectively. When this recipe is strictly applied, the calculation is consistent with the experimental limit for the 2ν lifetime of 48Ca and it also correctly reproduces the 2ν lifetime of 82Se. In this way, however, the two-neutrino matrix elements for the remaining nuclei are either underestimated (for 76Ge and 100Mo) or overestimated (for 128Te and 130Te) approximately by a factor of 3. With a comparatively small variation (< 10%) of the spin-triplet parameter, near the value suggested by the SU(4) symmetry, it is possible to reproduce the measured T2ν12 all the cases. The upper limit for the effective neutrino mass, as obtained from the theoretical estimates of 0ν matrix elements, is 〈m〉 ∼- 1 eV. The dependence of the nuclear matrix elements on the size of the configuration space has been also analyzed.

Four-tangle for pure states

An expression for four-tangle is obtained by examining the negativity fonts present in a four-way partial transpose under local unitary operations. An alternate derivation of three tangle is also given.

The Schrödinger cat state of trapped ions in harmonic and anharmonic oscillator traps

We examine the time evolution of a two-level ion interacting with a light field in a harmonic oscillator trap and in a trap with anharmonicities. The anharmonicities of the trap are quantified in terms of the deformation parameter τ characterizing the q-analogue of the harmonic oscillator trap. Initially the ion is prepared in a Schrodinger cat state. The entanglement of the centre-of-mass motional states and the internal degrees of freedom of the ion results in a characteristic collapse and revival pattern. We numerically calculate the population inversion I(t), quasi-probabilities Q(t) and partial mutual quantum entropy S(P) for the system as a function of time. Interestingly, small deformations of the trap enhance the contrast between population inversion collapse and revival peaks as compared to the zero-deformation case. For β = 3 and 4 (β determines the average number of trap quanta linked to centre-of-mass motion) the best collapse and revival sequence is obtained for τ = 0.0047 and 0.004, respectively. For large values of τ, decoherence sets are accompanied by loss of amplitude of population inversion, and for τ ~0.1 the collapse and revival phenomenon disappear. Each collapse or revival of population inversion is characterized by a peak in the S(P) versus t plot. During the transition from collapse to revival and vice-versa, we have a minimum mutual entropy value that is S(P) = 0. Successive revival peaks show a lowering of the local maximum point indicating a dissipative irreversible change in the ionic state. An improved definition of the collapse and revival pattern as the anharmonicity of the trapping potential increases is also reflected in the quasi-probability versus t plots.

Quantum coherences, K-way negativities and multipartite entanglement

A characterization of multipartite quantum states having

Intrinsic decoherence effects on tripartite GHZ state generation using a trapped ion coupled to an optical cavity

N

Classification of Multipartite Entanglement via Negativity Fonts

subsystems, based on negativities of matrices obtained by selective partial transposition of the state operator, is proposed. The

Local unitary invariants forN-qubit pure states

K

Generation of field mediated three qubit entangled state shared by Alice and Bob

-way partial transpose with respect to a subsystem is constructed by imposing constraints involving the states of

Multipartite entanglement of three trapped ions in a cavity and W-state generation

K

Tripartite GHZ state generation with trapped ion in an optical cavity

subsystems of the multipartite composite system. The