Comunicazione
Dynamics of open quantum systems: From the quantum Rabi model to coupled qubits.
Di Bello G., Cangemi L. M., Cataudella V., de Candia A., De Filippis G., Fazio R., Nocera A., Pavan F., Sassetti M., Perroni C.A.
Using the worldline Monte Carlo technique, Matrix Product State simulations, and a variational approach, we studied the equilibrium properties and relaxation features of the dissipative quantum Rabi model. This model involves a two-level system coupled to a harmonic oscillator in turn coupled to an Ohmic bath. By adjusting the qubit-oscillator interaction, we proved a Beretzinski-Kosterlitz-Thouless quantum phase transition in low bath coupling. We explored the dynamics of a slow qubit coupled to a fast oscillator and derived functional relationships between them. We examined the effects of internal and external couplings and evaluated the qubit Bloch vector. Interestingly, weak to intermediate bath coupling simplifies qubit state evaluation. In the ultra-strong coupling regime, we observe non-Markovian effects and entanglement growth. Recently, we focus on the effect of baths on other many-body open quantum systems, particularly two interacting qubits in an Ohmic bath. We demonstrate a method for obtaining quasi-fully non-decoherent qubit encoding. Our work sheds light on the behavior of open quantum systems and their potential for quantum computing and quantum communication.