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1.
We analyze generalized Gaussian cat states obtained by superposing arbitrary Gaussian states. The structure of the interference term of the Wigner function is always hyperbolic, surviving the action of a thermal reservoir. We also consider certain superpositions of mixed Gaussian states. An application to semiclassical dynamics is discussed. 相似文献
2.
Nonclassical correlations have been found useful in many quantum information processing tasks, and various measures have been proposed to quantify these correlations. In this work, we mainly study one of nonclassical correlations, called measurement-induced nonlocality (MIN). First, we establish a close connection between this nonlocal effect and the Bell nonlocality for two-qubit states. Then, we derive a tight monogamy relation of MIN for any pure three-qubit state and provide an alternative way to obtain similar monogamy relations for other nonclassical correlation measures, including squared negativity, quantum discord, and geometric quantum discord. Finally, we find that the tight monogamy relation of MIN is violated by some mixed three-qubit states, however, a weaker monogamy relation of MIN for mixed states and even multi-qubit states is still obtained. 相似文献
3.
The discriminating strength DS(ρAB) induced by local Gaussian unitary operators for any (n+m)-mode Gaussian state ρAB is introduced in[Phys. Rev. A 83 (2011) 042325]. In this paper, we further discuss the quantity by restricting to Hilbert-Schmidt norm. The analytic formulas of DS for two-mode squeezed thermal states and mixed thermal states are given. Then, the relationship between DS(ρAB) and DS((I ⊗ Φ)(ρAB)) for some special Gaussian channels Φ is discussed. In addition, DS is compared with Gaussian entanglement for symmetric squeezed thermal states. 相似文献
4.
《Physics letters. A》2020,384(1):126037
In bosonic fields, Gaussian states, which consist of a rather wide family of states including coherent states, squeezed states, thermal states, etc., have many classical-like features, and are usually defined from the mathematical perspective in terms of characteristic functions. It is well known that some special Gaussian states, such as coherent states, are minimum uncertainty states for the conventional Heisenberg uncertainty relation involving canonical pair of position and momentum observables. A natural question arises as whether all Gaussian states can be characterized as minimum uncertainty states. In this work, we show that indeed Gaussian states coincide with minimum uncertainty states for an information-theoretic refinement of the conventional uncertainty relation established in Luo (2005) [40]. This characterization puts Gaussian states on a novel basis of physical significance. 相似文献
5.
In this paper, we derive an explicit analytic expression of the
relative entropy between two general Gaussian states. In the
restriction of the set for Gaussian states and with the help of
relative entropy formula and Peres--Simon separability criterion,
one can conveniently obtain the relative entropy entanglement for
Gaussian states. As an example, the relative entanglement for a
two-mode squeezed thermal state has been obtained. 相似文献
6.
Dynamics of measurement-induced non-locality and geometric discord with initial system-environment correlations 下载免费PDF全文
We analyze the dynamics of geometric measure of discord (GMOD) and measurement-induced non-locality (MIN) in the presence of initial system-reservoir correlations without Born and Markov approximation. Although the initial system-environment states have the same reduced density matrices for both the system and environment, the effects of different initial system-environment correlations have been shown to fundamentally alter the time evolution of GMOD and MIN between two quantum systems in both Markovian and non-Markovian regimes. In general, both GMOD and MIN experience a sudden increase for initially quantum-correlated states, and a sudden decrease for classical-correlated states before they reach the same stationary values with initially factorized states. 相似文献
7.
A. Isar 《The European physical journal. Special topics》2008,160(1):225-234
Using the expression of the fidelity for the most general
Gaussian quantum states, the quantum fidelity is
studied for the states of a harmonic oscillator interacting with
an environment, in particular with a thermal bath. The time evolution
of the considered system is described in the framework of the
theory of open systems based on quantum dynamical semigroups. By taking a correlated squeezed Gaussian state as initial state,
we calculate
the quantum fidelity for both undisplaced and displaced
states. The time evolution of the quantum fidelity is analyzed depending on the squeezing and correlation parameters characterizing
the initial Gaussian state and on the dissipation constant and temperature of the thermal bath. 相似文献
8.
We define the degree of nonclassicality of a one-mode Gaussian state of the quantum electromagnetic field in terms of the Bures distance between the state and the set of all classical one-mode Gaussian states. We find the closest classical Gaussian state and the degree of nonclassicality using a recently established expression for the Uhlmann fidelity of two single-mode Gaussian states. The decrease of nonclassicality under thermal mapping is carefully analyzed. Along the same lines, we finally present the evolution of nonclassicality during linear amplification. 相似文献
9.
We propose the entropic measurement-induced nonlocality (MIN) as the maximal increment of von Neumann entropy induced by the locally non-disturbing measurement, and study its behaviors in both the independent and common structured reservoirs. We present schemes for preserving the MIN, and show that for certain initial states the MIN, including the quantum correlations, can even be enhanced by the common reservoir. Additionally, we also show that the different measures of MIN may give different qualitative characterizations of nonlocal properties, i.e., it is rather measure dependent than state dependent. 相似文献
10.
H. I. Nurdin 《Russian Journal of Mathematical Physics》2014,21(3):386-398
In this paper, we treat the quantum filtering problem for multiple input multiple output (MIMO) Markovian open quantum systems coupled to multiple boson fields in an arbitrary zero-mean jointly Gaussian state, using the reference probability approach formulated by Bouten and van Handel as a quantum version of a well-known method of the same name from classical nonlinear filtering theory, and exploiting the generalized Araki-Woods representation of Gough. This includes Gaussian field states such as vacuum, squeezed vacuum, thermal, and squeezed thermal states as special cases. The contribution is a derivation of the general quantum filtering equation (or stochastic master equation as they are known in the quantum optics community) in the full MIMO setup for any zero-mean jointly Gaussian input field states, up to some mild rank assumptions on certain matrices relating to the measurement vector. 相似文献
11.
Aurelian Isar 《Physics of Particles and Nuclei Letters》2009,6(7):567-571
Using the expression of the fidelity for the most general Gaussian quantum states, the behaviour of the quantum fidelity is described for the states of a harmonic oscillator interacting with an environment, in particular with a thermal bath. By taking a correlated squeezed Gaussian state as initial state, we calculate the quantum fidelity for both kinds of undisplaced and displaced states, and for different values of the squeezing and correlation parameters and of the environment temperature. 相似文献
12.
F. Dell'Anno S. De Siena L. Albano Farias F. Illuminati 《The European physical journal. Special topics》2008,160(1):115-126
We investigate continuous variable (CV) quantum teleportation using
relevant classes of non-Gaussian states of the radiation field as entangled resources.
First, we introduce the class two-mode squeezed symmetric superposition of Fock states,
including finite truncations of twin-beam Gaussian states as special realizations.
These states depend on a set of free independent parameters
that can be adjusted for the optimization of teleportation protocols,
with an enhancement of the success probability of teleportation
both for coherent and Fock input states.
We show that the optimization procedure reduces the entangled resources
to truncated twin beam states, which thus represents an optimal class
of non-Gaussian resources for quantum teleportation.
We then introduce a further class of two-mode non-Gaussian entangled resources,
in the form of squeezed cat-like states. We analyze the performance and the
properties of such states when optimized for (CV) teleportation,
and compare them to the optimized squeezed Bell-like states introduced
in a previous work [12]. We discuss how optimal resources for
teleportation are characterized by a suitable balance of entanglement content
and squeezed vacuum affinity.
We finally investigate the effects of thermal noise on the efficiency of
quantum teleportation. To this aim, a convenient framework is to describe
noisy entangled resources as linear superpositions of non-Gaussian state
and thermal states. Although the presence of the thermal component strongly
reduces the teleportation fidelity, noisy non-Gaussian states remain preferred resources when compared to noisy twin-beam
Gaussian states. 相似文献
13.
A. R. Usha Devi R. Prabhu M. S. Uma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(1):133-138
Production and analysis of non-Gaussian radiation fields has evinced a lot of attention recently.
Simplest way of generating such non-Gaussians is through adding (subtracting) photons to
Gaussian fields.
Interestingly, when photons are added to classical Gaussian fields, the resulting states exhibit
non-classicality.
Two important classical Gaussian radiation fields are coherent and thermal states. Here, we
study the non-classical features of
such states when photons are added to them. Non-classicality of these states shows up in the
negativity of the
Wigner function. We also work out the entanglement potential, a recently proposed measure
of non-classicality for these states. Our analysis reveals that photon added coherent states are
non-classical for all seed beam intensities; their non-classicality increases with the addition
of more number of photons. Thermal state exhibits non-classicality at all temperatures, when a
photon is added; lower the temperature, higher is their non-classicality. 相似文献
14.
Quantifying non-classical correlations under thermal effects in a double cavity optomechanical system 下载免费PDF全文
《中国物理 B》2020,(2)
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-Perot 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. 相似文献
15.
Measurement-induced nonlocality(MIN), a quantum correlation measure for bipartite systems,is an indicator of maximal global effects due to locally invariant von Neumann projective measurements. It is originally defined as the maximal square of the Hilbert-Schmidt norm of the difference between pre-and post-measurement states. In this article, we propose a new form of MIN based on affinity. This quantity satisfies all the criteria of a bona fide measure of quantum correlation measures. This quantity is evaluated for both arbitrary pure and 2×n dimensional(qubit-qudit) mixed states. The operational meaning of the proposed quantity is interpreted in terms of the interferometric power of the quantum state. We apply these results on two-qubit mixed states, such as the Werner, isotropic and Bell diagonal states. 相似文献
16.
Alfredo Luis 《Optics Communications》2007,273(1):173-181
We examine polarization properties of electromagnetic field states with Gaussian complex-amplitude distributions, such as quadrature coherent and squeezed states, thermal chaotic states, and two-mode squeezed vacuum states. We compute their polarization distribution and we apply to them diverse measures of degree of polarization and polarization fluctuations. This allows us to investigate the main properties of the degrees of polarization introduced so far. 相似文献
17.
S. -H. Xiang K. -H. Song W. Wen Z. -G. Shi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,62(2):289-296
We study entanglement properties of two-mode
squeezed thermal states subjected to two sources of decoherence: the
common reservoirs and the bosonic memory Gaussian channel. For the
former one, we find that there exist three different behaviors:
no-sudden death, sudden death, and no-creation of entanglement. The
range of parameters characterizing these processes is obtained. For
the latter one, we obtain a threshold in the degree of squeezing
above which the input states remain always entangled. Otherwise, no
entanglement is allowed in bosonic Gaussian channel with memory
effect. We show that a degree of memory for quantum channel can be
help to increase the initial entanglement, while the mean number of
added thermal photons is to fasten the decoherence
process. 相似文献
18.
19.
G. F. Zhang H. Fan A. L. Ji W. M. Liu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2012,66(2):34
By using geometric measure of discord (GMOD) [B. Dakić, V. Vedral, Č. Brukner, Phys. Rev. Lett. 105, 109502 (2010)] and measurement-induced nonlocality (MIN) [S. Luo, S. Fu, Phys. Rev. Lett. 106, 120401 (2011)], we investigate quantum correlation of a pair of two-level systems, each of which is interacting with a reservoir
at finite temperature T. We show that, for a broad class of states of the system, GMOD and MIN can endure sudden death, and there is no asymptotic
decay for MIN while asymptotic decay exists for GMOD. We also give the dynamics of GMOD and MIN with respect to the temperature
and illustrate their different characteristics. 相似文献
20.
Hideo Itoh Tatsuya Yamada Bruno Houssay Seiji Mukal Shin-ichiro Uekusa 《Optical Review》1994,1(2):150-152
System stability of various membership functions and fuzzy control methods are compared by numerical simulations to determine the feasibility of optoelectronic fuzzy inference method. An inverted pendulum is used for the destination system. A Gaussian membership function is better than a triangular one. MIN operations of grade evaluation and modification of consequent membership functions are better than other operations. SUM operation of consequent operation is better than MAX operation. 相似文献