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Concurrence Measurement for the Two-Qubit Optical and Atomic States

2015
*
Entropy
*

In

doi:10.3390/e17064293
fatcat:3bzdp6qkknaipassw7zqnnpkk4
*the*paper, we mainly review some direct*concurrence**measurement*protocols of*the**two*-*qubit**optical*or*atomic*system. We first introduce*the*concept of*concurrence**for*a*two*-*qubit*system. ... Second, we explain*the*approaches of*the**concurrence**measurement*in both a linear*and*a nonlinear*optical*system. ...*Measures**for**the**Atomic**State*Besides*the**optical*system,*the**concurrence**measurement*protocols*for*an*atomic**state*have also been investigated. ...##
###
Dynamics of quantum correlations and linear entropy in a multi-qubit-cavity system

2004
*
Journal of Optics B-Quantum and Semiclassical Optics
*

Specifically we investigate quantitative relations between

doi:10.1088/1464-4266/6/8/016
fatcat:65odorb5dzgelnh2k7noiyjcei
*the**concurrence**and*linear entropy*for*a*two*-*qubit*mixed system, implemented as*two**two*-level*atoms*interacting with a single-mode cavity field ... We present a theoretical study of*the*relationship between entanglement*and*entropy in multi-*qubit*quantum*optical*systems. ... Acknowledgments We acknowledge funding from*the*Clarendon Fund*and*ORS (AOC), DT-LINK (NFJ)*and*COLCIENCIAS project 1204-05-13614 (LQ). ...##
###
Entanglement evolution for quantum trajectories

2011
*
Journal of Physics, Conference Series
*

•

doi:10.1088/1742-6596/306/1/012029
fatcat:q4a3yxtjobbi3iwhvo42ak5fy4
*For**two**qubits*coupled to a common bath,*the*time behavior of*the*mean*concurrence*depends strongly on*the*initial*state*. One may have C(t) = C ρ(t) . ... Quantum*Optics*V,*Two*perfect photon counters make a click when a photon is emitted by*the**atom*i (i = A, B) • If D i detects a photon between t*and*t + dt,*the**qubits*suffer a quantum jump [occurs with ...##
###
Direct measurement of concurrence for atomic two-qubit pure states

2007
*
Physical Review A. Atomic, Molecular, and Optical Physics
*

We propose a general scheme to

doi:10.1103/physreva.75.032303
fatcat:icbkrg6xjra4xbajcdb3u56jmy
*measure**the**concurrence*of an arbitrary*two*-*qubit*pure*state*in*atomic*systems. ... We show that it is possible to encode*the**concurrence*in*the*probability of finding all*atomic**qubits*in*the*ground*state*. ...*The*authors are grateful to T. Schätz*for*useful discussions. ...##
###
Heralded entanglement of arbitrary degree in remote qubits

2009
*
Physical Review A. Atomic, Molecular, and Optical Physics
*

*The*degree of entanglement, as

*measured*by

*the*

*concurrence*, is found to be tunable by

*two*easily accessible experimental parameters. ... Incoherent scattering of photons off

*two*remote

*atoms*with a Lambda-level structure is used as a basic Young-type interferometer to herald long-lived entanglement of an arbitrary degree. ...

*the*

*qubit*formed by

*the*

*two*lower

*states*of

*atom*X (X = A, B). ...

##
###
Probing quantum entanglement, quantum discord, classical correlation, and the quantum state without disturbing them

2011
*
Physical Review A. Atomic, Molecular, and Optical Physics
*

In this paper, we present schemes

doi:10.1103/physreva.83.012317
fatcat:qrmwjculcvap5k22atikh4wtoa
*for*a type of one-parameter bipartite quantum*states*to probe*the*quantum entanglement,*the*quantum discord,*the*classical correlation*and**the*quantum*state*based on*the*... It is shown that our detection does not influence all these*measured*quantities. We also discuss how*the*spontaneous emission introduced by our probe*atom*influences our detection. ... Another*two*-level*atom*as a probe*qubit*interacts with*the**two**optical*cavity modes simultaneously. II. ...##
###
Proposal for direct measurement of concurrence via visibility in a cavity QED system

2008
*
Physical Review A. Atomic, Molecular, and Optical Physics
*

*The*scheme works

*for*any arbitrary pure initial

*state*of

*the*

*two*-

*qubit*cavity system. ... It is based on

*the*cavity-QED technology using

*atoms*as flying

*qubits*

*and*relies on

*the*identity of

*the*

*two*-particle visibility of

*the*

*atomic*probability with

*the*

*concurrence*of

*the*cavity system. ...

*The*proposed scheme to

*measure*

*the*

*concurrence*of a

*two*-

*qubit*cavity system.

*Atoms*1

*and*2 are prepared in their ground

*state*. ...

##
###
Entanglement generation in a system of two atomic quantum dots coupled to a pool of interacting bosons

2013
*
Physical Review A. Atomic, Molecular, and Optical Physics
*

*The*tripartite system of

*two*

*atomic*quantum dots

*and*a pool of bosons reduces to a

*qubit*-qutrit-

*qubit*realization. ...

*The*bipartite setup of only one

*atomic*quantum dot coupled to a pool of bosons turns out to be equivalent to

*two*

*qubits*which easily get entangled being initially in a product

*state*. ... Although an entanglement

*measure*is not unambiguously defined

*for*a tripartite hybrid system (one qutrit

*and*

*two*

*qubits*) one can calculate a

*concurrence*[34] : C(| ) = 3 − 3 i=1 Trρ 2 i , (12) where ρ ...

##
###
Position-dependent dynamics of two qubits in a leakage cavity

2008
*
Journal of Physics B: Atomic, Molecular and Optical Physics
*

*The*position-dependent entanglement dynamics of

*two*

*qubits*embedded in a leakage cavity is investigated.

*The*

*two*

*qubits*are initialled in Bell

*states*

*and*

*the*cavity mode is taken as a standing wave. ... It is found that (i)

*the*dynamics of

*the*Bell

*states*can be divided into

*two*groups according to one-photon entangled

*states*

*and*

*two*-photon entangled

*states*; (ii)

*the*entanglement life of

*the*one-photon ... Acknowledgments We would like to acknowledge

*the*support from

*the*National Natural Science Foundation of China under grant nos. 10575068, 10474062

*and*10547126, Shanghai Education Foundation

*for*Young ...

##
###
Reversing entanglement change by a weak measurement

2010
*
Physical Review A. Atomic, Molecular, and Optical Physics
*

*The*reversal procedure involves another weak

*measurement*, preceded

*and*followed by bit flips applied to both

*qubits*. ...

*For*

*the*amplitudedamping case,

*the*entanglement partially recovers under most conditions.

*For*

*the*weak-

*measurement*case,

*the*recovery of

*the*initial entangled

*state*is exact. ...

*State*map

*for*a single

*qubit*

*The*

*two*main operations in our scheme are amplitude damping

*and*weak

*measurement*. Here we discuss their

*state*maps in

*the*single-

*qubit*case

*for*better understanding. ...

##
###
Entanglement and Bell violation with phase decoherence or dissipation

2005
*
European Physical Journal D : Atomic, Molecular and Optical Physics
*

We adopt

doi:10.1140/epjd/e2005-00083-y
fatcat:xyu4klm4lrfirgsurodgv5efea
*the**concurrence*to characterize*the*entanglement between*atom**and*cavities or between*two**optical*cavities in*the*presence of*the*phase decoherence. ... Finally, we show that even if*the**atom*is initially prepared in a maximally mixed*state*, it can also entangle*the**two*mode cavity fields. ...*THE*ENTANGLEMENT BETWEEN*ATOM**AND*CAVITIES OR*TWO**OPTICAL*CAVITIES In order to quantify*the*degree of entanglement, several*measures*[13] of entanglement have been introduced*for*both pure*and*mixed ...##
###
Controlling Entanglement Dynamics by Choosing Appropriate Ratio between Cavity-Fiber Coupling and Atom-Cavity Coupling

2010
*
Communications in Theoretical Physics
*

*The*entanglement characteristics including

*the*so-called sudden death effect between

*two*identical

*two*-level

*atoms*trapped in

*two*separate cavities connected by an

*optical*fiber are studied. ...

*The*results show that

*the*time evolution of entanglement is sensitive not only to

*the*degree of entanglement of

*the*initial

*state*but also to

*the*ratio between cavity-fiber coupling ()

*and*

*atom*-cavity ...

*The*

*concurrence*( ) C ρ

*for*

*the*reduced density matrix ρ of a

*two*-

*qubit*system is defined as arranged in decreasing order. ...

##
###
Scheme for on-resonance generation of entanglement in time-dependent asymmetric two-qubit-cavity systems

2004
*
Physical Review A. Atomic, Molecular, and Optical Physics
*

We present an efficient scheme

doi:10.1103/physreva.70.020301
fatcat:3dtpm2d4yzbnfme6ipi7t3w3mq
*for**the*controlled generation of pure*two*-*qubit**states*possessing any desired degree of entanglement*and*a prescribed symmetry in*two*cavity QED based systems, namely, cold ... trapped ions*and*flying*atoms*. ... We investigate*the*dynamical evolution of*the**concurrence*C(ρ a,a ) which*measures**the*degree of*two*-*qubit*entanglement [10] ,*and**the**two*-*qubit*correlation function σ + 2 σ − 1 which*measures**the*degree ...##
###
Protecting quantum entanglement from amplitude damping

2013
*
Journal of Physics B: Atomic, Molecular and Optical Physics
*

Quantum entanglement is a critical resource

doi:10.1088/0953-4075/46/14/145501
fatcat:vvy7prvm5zdphp6lizjazbkf7u
*for*quantum information*and*quantum computation. ... As opposed to some recently studied methods,*the*scheme presented here does not require weak*measurement*in*the*reversal process, leading to a faster recovery of entanglement. ... ACKNOWLEDGMENT This work is supported by grants from*the*King Abdulaziz City*for*Science*and*Technology (KACST)*and*from*the*Qatar National Research Fund (QNRF) under*the*NPRP project 4-520-1-083. ...##
###
Quantum entanglement for two qubits in a nonstationary cavity

2016
*
Physical Review A
*

*The*quantum entanglement

*and*

*the*probability of

*the*dynamical Lamb effect

*for*

*two*

*qubits*caused by non-adiabatic fast change of

*the*boundary conditions are studied. ...

*The*conditional

*concurrence*of

*the*

*qubits*

*for*each fixed number of created photons in a nonstationary cavity is obtained as a

*measure*of

*the*dynamical quantum entanglement due to

*the*dynamical Lamb effect ... It is well-known that

*the*possible

*measure*of quantum entanglement of

*two*

*qubits*is

*the*

*concurrence*C [21] [22] [23] , defined

*for*

*the*

*two*-

*qubit*

*state*|Φ |Φ = a |00 + b |01 + c |10 + d |11 (19) as C(Φ ...

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