arXiv subjects

Francesco V. Pepe

Publications and source records attributed to Francesco V. Pepe.

60 records · Page 4Linked to original sources

arXiv2015

Typical observables in a two-mode Bose system

A class of k-particle observables in a two-mode system of Bose particles is characterized by typicality: if the state of the system is sampled out of a suitable ensemble, an experimental measurement of that observable yields (almost) always the same result. We investigate the general features of typical observables, the criteria to determine typicality and finally focus on the case of density correlation functions, which are related to spatial distribution of particles and interference.

quant-ph↗

arXiv2014

Phase randomization and typicality in the interference of two condensates

Interference is observed when two independent Bose-Einstein condensates expand and overlap. This phenomenon is typical, in the sense that the overwhelming majority of wave functions of the condensates, uniformly sampled out of a suitable portion of the total Hilbert space, display interference with maximal visibility. We focus here on the phases of the condensates and their (pseudo) randomization, which naturally emerges when two-body scattering processes are considered. Relationship to typicality is discussed and analyzed.

cond-mat.quant-gas↗

arXiv2014

Multipartite entanglement and few-body Hamiltonians

We investigate the possibility to obtain higly multipartite-entangled states as nondegenerate eigenstates of Hamiltonians that involve only short-range and few-body interactions. We study small-size systems (with a number of qubits ranging from three to five) and search for Hamiltonians with a Maximally Multipartite Entangled State (MMES) as a nondegenerate eigenstate. We then find conditions, including bounds on the number of coupled qubits, to build a Hamiltonian with a Greenberger-Horne-Zeilinger (GHZ) state as a nondegenerate eigenstate. We finally comment on possible applications.

quant-ph↗

arXiv2012

Unearthing wave-function renormalization effects in the time evolution of a Bose-Einstein condensate

We study the time evolution of a Bose-Einstein condensate in an accelerated optical lattice. When the condensate has a narrow quasimomentum distribution and the optical lattice is shallow, the survival probability in the ground band exhibits a steplike structure. In this regime we establish a connection between the wave-function renormalization parameter $Z$ and the phenomenon of resonantly enhanced tunneling.

quant-ph↗

arXiv2012

Domain wall suppression in trapped mixtures of Bose-Einstein condensates

The ground state energy of a binary mixture of Bose-Einstein condensates can be estimated for large atomic samples by making use of suitably regularized Thomas-Fermi density profiles. By exploiting a variational method on the trial densities the energy can be computed by explicitly taking into account the normalization condition. This yields analytical results and provides the basis for further improvement of the approximation. As a case study, we consider a binary mixture of $^{87}$Rb atoms in two different hyperfine states in a double well potential and discuss the energy crossing between density profiles with different numbers of domain walls, as the number of particles and the inter-species interaction vary.

cond-mat.quant-gas↗

arXiv2011

Greenberger-Horne-Zeilinger states and few-body Hamiltonians

The generation of Greenberger-Horne-Zeilinger (GHZ) states is a crucial problem in quantum information. We derive general conditions for obtaining GHZ states as eigenstates of a Hamiltonian. In general, degeneracy cannot be avoided if the Hamiltonian contains m-body interaction terms with m<=2 and a number of qubits strictly larger than 4. As an application, we explicitly construct a two-body 4-qubit Hamiltonian and a three-body 5-qubit Hamiltonian that exhibit a GHZ as a nondegenerate eigenstate.

quant-ph↗