Search results for "quantum entanglement"
showing 10 items of 320 documents
Effect of Static Disorder in an Electron-Fabry Perot Interferometr with Two Quantum Scattering Centers
2007
In a recent paper -- F. Ciccarello \emph{et al.}, New J. Phys. \textbf{8}, 214 (2006) -- we have demonstrated that the electron transmission properties of a one-dimensional (1D) wire with two identical embedded spin-1/2 impurities can be significantly affected by entanglement between the spins of the scattering centers. Such effect is of particular interest in the control of transmission of quantum information in nanostructures and can be used as a detection scheme of maximally entangled states of two localized spins. In this letter, we relax the constraint that the two magnetic impurities are equal and investigate how the main results presented in the above paper are affected by a static d…
Gain tuning for continuous-variable quantum teleportation of discrete-variable states
2013
We present a general formalism to describe continuous-variable (CV) quantum teleportation of discrete-variable (DV) states with gain tuning, taking into account experimental imperfections. Here the teleportation output is given by independently transforming each density matrix element of the initial state. This formalism allows us to accurately model various teleportation experiments and to analyze the gain dependence of their respective figures of merit. We apply our formalism to the recent experiment of CV teleportation of qubits [S. Takeda et al., Nature 500, 315 (2013)] and investigate the optimal gain for the transfer fidelity. We also propose and model an experiment for CV teleportati…
Coupling-assisted Landau-Majorana-Stückelberg-Zener transition in a system of two interacting spin qubits
2019
We analyse a system of two interacting spin-qubits subjected to a Landau-Majorana-Stuckelberg-Zener (LMSZ) ramp. We prove that LMSZ transitions of the two spin-qubits are possible without an external transverse static field since its role is played by the coupling between the spin-qubits. We show how such a physical effect could be exploited to estimate the strength of the interaction between the two spin-qubits and to generate entangled states of the system by appropriately setting the slope of the ramp. Moreover, the study of effects of the coupling parameters on the time-behaviour of the entanglement is reported. Finally, our symmetry-based approach allows us to discuss also effects stem…
Dissipation-induced stationary entanglement in dipole-dipole interacting atomic samples
2004
The dynamics of two two-level dipole-dipole interacting atoms coupled to a common electro-magnetic bath and closely located inside a lossy cavity, is reported. Initially injecting only one excitation in the two-atom cavity system, loss mechanisms asymptotically drive the matter sample toward a stationary maximally entangled state. The role played by the closeness of the two atoms, with respect to such a cooperative behavior, is carefully discussed. Stationary radiation trapping effects are found and transparently interpreted.
Controlled insertion of one and two atoms into a high-finesse optical cavity
2007
Entangled quantum states have applications as a model system for strongly correlated many body states, as resource for quantum information processing and as a tool for enhanced precision measurements. Deterministic entanglement schemes create the desired state by transferring the system under the action of a carefully chosen Hamiltonian into an entangled state. The system must follow a unitary evolution, and uncontrolled parasitic interactions with the environment leading to spontaneous decay or partial measurements of the state have to be avoided. The paper present an experiment, on loading a chosen number of Doppler-cooled caesium atoms from a magneto-optical trap into a standing wave opt…
Continuous variable quantum teleportation with non-Gaussian resources
2007
We investigate continuous variable quantum teleportation using non-Gaussian states of the radiation field as entangled resources. We compare the performance of different classes of degaussified resources, including two-mode photon-added and two-mode photon-subtracted squeezed states. We then introduce a class of two-mode squeezed Bell-like states with one-parameter dependence for optimization. These states interpolate between and include as subcases different classes of degaussified resources. We show that optimized squeezed Bell-like resources yield a remarkable improvement in the fidelity of teleportation both for coherent and nonclassical input states. The investigation reveals that the …
Infinite projected entangled pair states algorithm improved: Fast full update and gauge fixing
2015
© 2015 American Physical Society. ©2015 American Physical Society. The infinite projected entangled pair states (iPEPS) algorithm [J. Jordan, Phys. Rev. Lett. 101, 250602 (2008)PRLTAO0031-900710.1103/PhysRevLett.101.250602] has become a useful tool in the calculation of ground-state properties of two-dimensional quantum lattice systems in the thermodynamic limit. Despite its many successful implementations, the method has some limitations in its present formulation which hinder its application to some highly entangled systems. The purpose of this paper is to unravel some of these issues, in turn enhancing the stability and efficiency of iPEPS methods. For this, we first introduce the fast f…
Simulating long-distance entanglement in quantum spin chains by superconducting flux qubits
2014
We investigate the performance of superconducting flux qubits for the adiabatic quantum simulation of long distance entanglement (LDE), namely a finite ground-state entanglement between the end spins of a quantum spin chain with open boundary conditions. As such, LDE can be considered an elementary precursor of edge modes and topological order. We discuss two possible implementations which simulate open chains with uniform bulk and weak end bonds, either with Ising or with XX nearest-neighbor interactions. In both cases we discuss a suitable protocol for the adiabatic preparation of the ground state in the physical regimes featuring LDE. In the first case the adiabatic manipulation and the …
Resetting of a planar superconducting quantum memory
2009
We consider and analyze a scheme for the reset of a M × N planar array of inductively coupled Josephson flux qubits. We prove that it is possible to minimize the resetting time of an arbitrary chosen row of qubits by properly switching on and off the coupling between pairs of qubits belonging to the same column. In addition, the analysis of the time evolution of the array allows us to single out the class of generalized W states which can be successfully reset.