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Giuseppe Liberti

Publications and source records attributed to Giuseppe Liberti.

4 recordsLinked to original sources
arXiv2009

On the finite size behavior of quantum collective spin systems

We discuss the finite size behavior of the adiabatic Dicke model, describing the collective coupling of a set of N-two level atoms (qubits) to a faster (electromagnetic) oscillator mode. The energy eigen-states of this system are shown to be directly related to those of another widely studied collective spin model, the uniaxial one. By employing an approximate continuum approach, we obtain a complete characterization of the properties of the latter, which we then use to evaluate the scaling properties of various observables for the original Dicke model near its quantum phase transition.

quant-ph↗
arXiv2006

Scaling of Berry's Phase Close to the Dicke Quantum Phase Transition

We discuss the thermodynamic and finite size scaling properties of the geometric phase in the adiabatic Dicke model, describing the super-radiant phase transition for an $N$ qubit register coupled to a slow oscillator mode. We show that, in the thermodynamic limit, a non zero Berry phase is obtained only if a path in parameter space is followed that encircles the critical point. Furthermore, we investigate the precursors of this critical behavior for a system with finite size and obtain the leading order in the 1/N expansion of the Berry phase and its critical exponent.

quant-ph↗
arXiv2005

Thermodynamic properties of the Dicke model in the strong-coupling regime

We discuss the problem of a N two-level systems interacting with a single radiation mode in the strong-coupling regime. The thermodynamic properties of Dicke model are analyzed developing a perturbative expansion of the partition function in the high-temperature limit and we use this method to investigate the connections between the Dicke and the collective one-dimensional Ising model

cond-mat.stat-mech↗