Thermal and Magnetic Quantum Discord in Heisenberg models (2009)
We investigate how the quantum correlations (quantum discord) of a two-qubit one dimensional XYZ Heisenberg chain in thermal equilibrium depends on the temperature (T) of the bath and also on an...
Unity fidelity multiple teleportation using partially entangled states (2008)
We show that the recent multiple teleportation protocol (MTP) presented in Ref. [Phys. Rev. Lett. 100, 110503 (2008)] is not restricted to the Knill-Laflamme-Milburn (KLM) scheme. Rather, we show...
Quantum cryptography using partially entangled states (2008)
Gordon, Goren, Rigolin, Gustavo
We show that non-maximally entangled states can be used to build a quantum key distribution (QKD) scheme whose security and key rate transmission is nearly equivalent to those of standard QKD...
Rigolin, Gustavo, De Oliveira, Marcos C.
We propose a strictly local quantum tomography protocol for a bipartite system. We show that the joint density matrix of an arbitrary two-mode Gaussian state, entangled or not, is obtained via local...
Beyond the Quantum Adiabatic Approximation: Adiabatic Perturbation Theory (2008)
Rigolin, Gustavo, Ortiz, Gerardo, Ponce, Victor Hugo
We introduce a perturbative approach to solving the time dependent Schroedinger equation, named adiabatic perturbation theory (APT), whose zeroth order term is the quantum adiabatic approximation....
Symmetry breaking effects upon bipartite and multipartite entanglement in the XY model (2007)
De Oliveira, Thiago R., Rigolin, Gustavo, De Oliveira, Marcos C., Miranda, E.
We analyze the bipartite and multipartite entanglement for the ground state of the one-dimensional XY model in a transverse magnetic field in the thermodynamical limit. We explicitly take into...
Generalized Quantum Telecloning (2007)
Gordon, Goren, Rigolin, Gustavo
We present a generalized telecloning (GTC) protocol where the quantum channel is non-optimally entangled and we study how the fidelity of the telecloned states depends on the entanglement of the...
Haruna, Luis F., De Oliveira, Marcos C., Rigolin, Gustavo
We develop the minimal requirements for the complete entanglement quantification of an arbitrary two-mode bipartite Gaussian state via local measurements and a classical communication channel. The...
Quantum channels in random spin chains (2006)
Hoyos, Jose A., Rigolin, Gustavo
We study the entanglement between pairs of qubits in a random antiferromagnetic spin-1/2 chain at zero temperature. We show that some very distant pairs of qubits are highly entangled, being almost...
Quantification of Continuous Variable Entanglement with only Two Types of Simple Measurements (2006)
Rigolin, Gustavo, De Oliveira, Marcos C.
Here we propose an experimental set-up in which it is possible to measure the entanglement of a two-mode Gaussian state, be it pure or mixed, using only simple linear optical devices. After a proper...
Multipartite Entanglement Signature of Quantum Phase Transitions (2006)
De Oliveira, Thiago R., Rigolin, Gustavo, De Oliveira, Marcos C., Miranda, Eduardo
We derive a general relation between the non-analyticities of the ground state energy and those of a subclass of the multipartite generalized global entanglement (GGE) measure defined by T. R. de...
Generalized Quantum State Sharing (2006)
Gordon, Goren, Rigolin, Gustavo
We present two quantum state sharing protocols where the channels are not maximally entangled states. By properly choosing the measurement basis it is possible to achieve unity fidelity transfer of...
Operational Classification and Quantification of Multipartite Entangled States (2006)
Rigolin, Gustavo, De Oliveira, Thiago R., De Oliveira, Marcos C.
We formalize and extend an operational multipartite entanglement measure introduced by T. R. Oliveira, G. Rigolin, and M. C. de Oliveira, Phys. Rev. A 73, 010305(R) (2006), through the generalization...
Introdução à criptografia quântica (2005)
Rigolin,Gustavo, Rieznik,Andrés Anibal
Apresentamos de maneira detalhada os quatro protocolos de distribuição de chaves que fundaram a importante área da criptografia quântica, numa linguagem acessível a alunos de graduação em...
Introduction to Quantum Cryptography (2005)
Rigolin, Gustavo, Rieznik, Andres A.
We show in details the four quantum key distribution protocols which initiated the important field of quantum cryptography, using an accessible language for undergraduate students. We begin...
Generalized Teleportation Protocol (2005)
Gordon, Goren, Rigolin, Gustavo
A generalized teleportation protocol (GTP) for N qubits is presented, where the teleportation channels are non-maximally entangled and all the free parameters of the protocol are considered: Alice's...
A New Simple Derivation of Schroedinger Uncertainty Relation (2005)
We show how the Schroedinger Uncertainty Relation for a pair of observables can be deduced using the Cauchy-Schwarz inequality plus successive applications of the commutation relation involving the...
Genuine Multipartite Entanglement in Quantum Phase Transitions (2005)
De Oliveira, Thiago R., Rigolin, Gustavo, De Oliveira, Marcos C.
We demonstrate that the Global Entanglement (GE) measure defined by Meyer and Wallach, J. Math. Phys. 43, 4273 (2002), is maximal at the critical point for the Ising chain in a transverse magnetic...