In Li and Luo(2007 Phys.Rev.A 76032327),the inequality(1/2)T≥Q was identified as a fundamental postulate for a consistent theory of quantum versus classical correlations for arbitrary measures of total T and quantum ...In Li and Luo(2007 Phys.Rev.A 76032327),the inequality(1/2)T≥Q was identified as a fundamental postulate for a consistent theory of quantum versus classical correlations for arbitrary measures of total T and quantum Q correlations in bipartite quantum states.Besides,Hayden et al(2006 Commun.Math.Phys.26595)have conjectured that,in some conditions within systems endowed with infinite-dimensional Hilbert spaces,quantum correlations may dominate not only half of total correlations but total correlations itself.Here,in a two-mode Gaussian state,quantifying T and Q respectively by the quantum mutual information I~G and the entanglement of formation(EoF)ε_(F)^(G),we verify thatε_(F)^(G),is always less than(1/2)I_(R)^(G( when I~G andε_(F)^(G) are defined via the Rényi-2 entropy.While via the von Neumann entropy,ε_(F,V)^(G),may even dominate I_(V)^(G) itself,which partly consolidates the Hayden conjecture,and partly,provides strong evidence hinting that the origin of this counterintuitive behavior should intrinsically be related to the von Neumann entropy by which the EoFε_(F,V)^(G),is defined,rather than related to the conceptual definition of the EoFε_(F).The obtained results show that—in the special case of mixed two-mode Gaussian states—quantum entanglement can be faithfully quantified by the Gaussian Rényi-2 EoFε_(F,R)^(G),.展开更多
We investigate the generation of quantum correlations between mechanical modes and optical modes in an optomechanical system,using the rotating wave approximation.The system is composed of two Fabry-Pérot cavitie...We investigate the generation of quantum correlations between mechanical modes and optical modes in an optomechanical system,using the rotating wave approximation.The system is composed of two Fabry-Pérot cavities separated in space;each of the two cavities has a movable end-mirror.Our aim is the evaluation of entanglement between mechanical modes and optical modes,generated by correlations transfer from the squeezed light to the system,using Gaussian intrinsic entanglement as a witness of entanglement in continuous variables Gaussian states,and the quantification of the degree of mixedness of the Gaussian states using the purity.Then,we quantify nonclassical correlations between mechanical modes and optical modes even beyond entanglement by considering Gaussian geometric discord via the Hellinger distance.Indeed,entanglement,mixdness,and quantum discord are analyzed as a function of the parameters characterizing the system(thermal bath temperature,squeezing parameter,and optomechanical cooperativity).We find that,under thermal effect,when entanglement vanishes,purity and quantum discord remain nonzero.Remarkably,the Gaussian Hellinger discord is more robust than entanglement.The effects of the other parameters are discussed in detail.展开更多
We investigate the local quantum uncertainty(LQU)in weak measurement.An expression of weak LQU is explicitly determined.Also,we consider some cases of three special X states,Werner state,circulant two-qubit states,and...We investigate the local quantum uncertainty(LQU)in weak measurement.An expression of weak LQU is explicitly determined.Also,we consider some cases of three special X states,Werner state,circulant two-qubit states,and Heisenberg model via LQU in normal and weak measurements.We find that the LQU in weak measurement is weaker than the case of strong measurement.展开更多
基金I am particularly indebted to an anonymous referee for constructive critiques and insightful comments.
文摘In Li and Luo(2007 Phys.Rev.A 76032327),the inequality(1/2)T≥Q was identified as a fundamental postulate for a consistent theory of quantum versus classical correlations for arbitrary measures of total T and quantum Q correlations in bipartite quantum states.Besides,Hayden et al(2006 Commun.Math.Phys.26595)have conjectured that,in some conditions within systems endowed with infinite-dimensional Hilbert spaces,quantum correlations may dominate not only half of total correlations but total correlations itself.Here,in a two-mode Gaussian state,quantifying T and Q respectively by the quantum mutual information I~G and the entanglement of formation(EoF)ε_(F)^(G),we verify thatε_(F)^(G),is always less than(1/2)I_(R)^(G( when I~G andε_(F)^(G) are defined via the Rényi-2 entropy.While via the von Neumann entropy,ε_(F,V)^(G),may even dominate I_(V)^(G) itself,which partly consolidates the Hayden conjecture,and partly,provides strong evidence hinting that the origin of this counterintuitive behavior should intrinsically be related to the von Neumann entropy by which the EoFε_(F,V)^(G),is defined,rather than related to the conceptual definition of the EoFε_(F).The obtained results show that—in the special case of mixed two-mode Gaussian states—quantum entanglement can be faithfully quantified by the Gaussian Rényi-2 EoFε_(F,R)^(G),.
文摘We investigate the generation of quantum correlations between mechanical modes and optical modes in an optomechanical system,using the rotating wave approximation.The system is composed of two Fabry-Pérot cavities separated in space;each of the two cavities has a movable end-mirror.Our aim is the evaluation of entanglement between mechanical modes and optical modes,generated by correlations transfer from the squeezed light to the system,using Gaussian intrinsic entanglement as a witness of entanglement in continuous variables Gaussian states,and the quantification of the degree of mixedness of the Gaussian states using the purity.Then,we quantify nonclassical correlations between mechanical modes and optical modes even beyond entanglement by considering Gaussian geometric discord via the Hellinger distance.Indeed,entanglement,mixdness,and quantum discord are analyzed as a function of the parameters characterizing the system(thermal bath temperature,squeezing parameter,and optomechanical cooperativity).We find that,under thermal effect,when entanglement vanishes,purity and quantum discord remain nonzero.Remarkably,the Gaussian Hellinger discord is more robust than entanglement.The effects of the other parameters are discussed in detail.
文摘We investigate the local quantum uncertainty(LQU)in weak measurement.An expression of weak LQU is explicitly determined.Also,we consider some cases of three special X states,Werner state,circulant two-qubit states,and Heisenberg model via LQU in normal and weak measurements.We find that the LQU in weak measurement is weaker than the case of strong measurement.
