THE DISSIPATIVE TWO–STATE SYSTEM

Subhashish Banerjee

Alessandro Sergi, Konstantin G. Zloshchastiev

We consider a non-Hermitian Hamiltonian in order to effectively describe a two-level system (TLS) coupled to a generic dissipative environment. The total Hamiltonian of the model is obtained by adding a general anti-Hermitian part, depending on four parameters, to the Hermitian Hamiltonian of a tunneling TLS. The time evolution is formulated and derived in terms of the normalized density operator of the model, different types of decays are revealed and analyzed. In particular, the population difference and coherence are defined and calculated analytically. We have been able to mimic various physical situations with different properties, such as dephasing, vanishing population difference and purification.

Sushanta Dattagupta, Sanjay Puri

Y Hang

In this paper, a two-phonon coherent state has been introduced to investigate the influence of coupling with a quantum tunneling system on phonon states. Comparing with usual one-phonon coherent state, this new phonon slate has the following properties: (1) Its energy is renormalized by the quantum tunneling system; (2) Its suppression effect on the renormalized tunneling parameter is reduced; (3) It makes the whole system in a more stable ground state.