Alladi Ramakrishnan Hall

Generalized spin kitten states in a strongly coupled spin-oscillator system

M. Balamurugan

Department of Theoretical Physics, Madras University

Utilizing an adiabatic approximation method, a bipartite qudit-oscillator
Hamiltonian is studied for low-spin values (s=1 and s=3/2) in both strong and
ultrastrong coupling regimes. The quasiprobability densities on the hybrid factorized
phase space are introduced. Integrating over a sector of the composite phase space,
the quasiprobability distributions of its complementary subsystem are recovered. In
the strong coupling regime, the qudit entropy displays a pattern of quasiperiodic
collapses and revivals. Starting with a bipartite factorizable initial state, we observe
that almost pure spin kitten type states dynamically develop at near-null values of
entropy. The Hilbert-Schmidt distance measure of these states puts them metrically
far away from the initial state. Other localized spin states form at locally minimum
but significantly large values of entropy. The evolution to the nonclassical transitory
spin states is displayed via the diagonal spin P-representation. As another
manifestation of nonclassicality the emergence of the spin-squeezed states during the
bipartite evolution is observed. In the ultrastrong coupling domain, a large number of
interaction-dependent modes and their harmonics are generated. The consequent
randomization of the phases eliminates the quasiperiodicity of the system which is
now driven towards a stabilization of the entropy that also undergoes stochastic
fluctuations around a suitably stabilized value. In both the strong and ultrastrong
coupling realms, antibunching of the photoemission events is realized particularly for
the small spin values.