共查询到18条相似文献,搜索用时 734 毫秒
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用费米线性光学方法,提出无相互作用费米量子信道物理模型.用平稳量子高斯态协方差矩阵性质及Majorization不等式理论,推导出在平稳高斯输入态下费米量子信道最小输出熵的表达式.利用在n模费米系统添加一个额外模的方法,得到平稳高斯态和高斯态输出熵的关系|利用此关系式,借助在高斯输入态下费米信道最小输出熵值是可达的猜测,推导出无相互作用费米信道直积态容量的表达式.最后,用最小输出熵的迭代算法验证已推出的费米信道最小输出熵表达式正确性,数值计算结果表明:对于带噪声的无相互作用费米量子信道,已推出最小输出熵与数值计算结果的吻合度可以达到10e-9. 相似文献
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与经典通信相类似,量子高斯噪声是一种重要的量子噪声模型.这里,"经典"是相对于"量子"而言的.讨论量子高斯信道传送经典信息时的信息容量,也称量子信道的经典容量,是量子通信的热点问题之一.文中在量子高斯态、高斯熵性质和Holevo界基础上,给出单用户量子高斯信道的经典容量,借助多址量子信道的经典容量区域定理,通过坐标系变换方法,从理论上推导得到多用户量子高斯信道的经典容量区域.为了计算简便且不失一般性,计算过程将采用两输入、单输出的量子多址信道模型进行说明,结论可类推到n个输入、单输出的多址信道. 相似文献
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基于Braunstein和Kimble方案以双模压缩真空态作为量子信道实施对单模最小关联混态量子隐性传态的可行性进行了研究.我们发现,单模最小关联混态在一定参数范围内呈现出压缩效应这种非经典性质,利用双模压缩真空态作为量子通道可以高保真的传递没有压缩效应的单模最小关联混态,但对呈现压缩效应的单模最小关联混态进行量子隐性传送时得到输出态的保真度较低.而且发现通过调节输出端位移因子的方法不能实现对单模最小关联混态保真度的优化. 相似文献
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基于Braunstein和Kimble提出的B-K方案以双模最小关联混合态作为量子信道实施对未知量子态的隐形传送,并以传送相干态为例进行了研究.结果表明:双模最小关联混合态作为一种广义的Einstein-Podolsky-Rosen型纠缠态在实现量子隐形传态中能很好地担当量子信道的角色,在纠缠度和压缩度选择适当的条件下被传送未知量子态的保真度可以达到1.这是比双模压缩真空态更优越的量子信道.
关键词:
量子隐形传态
双模最小关联混合态
保真度 相似文献
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利用量子信道和经典信道相结合的方法,采用部分脱体传输设计了连续变量1→2量子克隆方案,在此基础上研究了克隆保真度与EPR导引之间的关系。研究结果表明:双向量子导引态是实现相干态安全量子克隆的必要资源。对于克隆输出模Clone 1,取最优增益时克隆保真度超过不可克隆阈值的实现需要共享纠缠源的双向导引,但并不是所有双向导引的资源都能使克隆的保真度大于■。在输出模Clone 1的最优增益下,观察了输出模Clone 1和输出模Clone 2的保真度随分束器反射率和压缩参数的变化,发现使用纠缠度较小但可导引的资源可以实现较高的克隆保真度,且克隆过程中也不需要较高的反射率。此研究结果对安全量子通信网络的构建具有一定的参考意义。 相似文献
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极化自由度对分束器出射光场的量子相干性影响的研究 总被引:1,自引:0,他引:1
我们在讨论粒子数态光场在分束器上干涉后得到的输出态的量子相干性时,考虑了入射场的极化自由度.利用campos[1]等人提出的量子分束器的SU(2)理论模型,计算得到了输出光场所处状态的表达式.进而讨论了光场在两个不同的入射空间模上极化方向对两个输出空间模上光场二阶量子干涉度的影响. 相似文献
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Hong-yi Fan 《Annals of Physics》2007,322(4):886-902
The Newton-Leibniz integration over Dirac’s ket-bra operators introduced in Ref. [Hong-yi Fan, Hai-liang Lu, Yue Fan, Ann. Phys. 321 (2006) 480-494] is generalized to Newton-Leibniz-Berezin integration over fermionic ket-bra projection operators, the corresponding technique of integration within an ordered product (IWOP) of Fermi operators is proposed which is then used to develop fermionic quantum statistics. The generalized partition function formula of multi-mode quadratic interacting fermion is derived via the fermionic coherent state representation and the IWOP technique. The two-mode fermionic squeezing operators and their group property studied by their fermionic coherent state representation as well as fermionic permutation operator are also deduced in this way. Thus Dirac’s symbolic method for Fermi system can also be developed, which exhibits Bose-Fermi supersymmetry in this aspect. 相似文献
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With some reviews on the investigations on the schemes for quantum state transfer based on spin systems, we discuss the quantum
dynamics of magnetically-controlled networks for Bloch electrons. The networks are constructed by connecting several tight-binding
chains with uniform nearest-neighbor hopping integrals. The external magnetic field and the connecting hopping integrals can
be used to control the intrinsic properties of the networks. For several typical networks, rigorous results are shown for
some specific values of external magnetic field and the connecting hopping integrals: a complicated network can be reduced
into a virtual network, which is a direct sum of some independent chains with uniform nearest-neighbor hopping integrals.
These reductions are due to the fermionic statistics and the Aharonov-Bohm effects. In application, we study the quantum dynamics
of wave packet motion of Bloch electrons in such networks. For various geometrical configurations, these networks can function
as some optical devices, such as beam splitters, switches and interferometers. When the Bloch electrons as Gaussian wave packets
input these devices, various quantum coherence phenomena can be observed, e.g., the perfect quantum state transfer without
reflection in a Y-shaped beam, the multi-mode entanglers of electron wave by star-shaped network, magnetically controlled
switches, and Bloch electron interferometer with the lattice Aharonov-Bohm effects. With these quantum coherent features,
the networks are expected to be used as quantum information processors for the fermion system based on the possible engineered
solid state systems, such as the array of quantum dots that can be implemented experimentally.
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We discuss the quantum phase transition that separates a vacuum state with fully gapped fermion spectrum from a vacuum state with topologically protected Fermi points (gap nodes). In the context of condensed-matter physics, such a quantum phase transition with Fermi point splitting may occur for a system of ultracold fermionic atoms in the region of BEC-BCS crossover, provided Cooper pairing occurs in the non-s-wave channel. For elementary particle physics, the splitting of Fermi points may lead to CPT violation, neutrino oscillations, and other phenomena. 相似文献
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On the basis of the fermionic coherent state formulation we propose the weyl-McCoy correspondence for fermion system, from which a functional integral form without the boundary term is derived. Moreover, the generating functional, the wigner theorem. and the Moyal bracket for fermion system are also demonstrated. Thus the theory of quantum mechanics for Fermi operators and its pseudo-classical correspondence is established. 相似文献
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Haegeman J Cirac JI Osborne TJ Verschelde H Verstraete F 《Physical review letters》2010,105(25):251601
We extend the recently introduced continuous matrix product state variational class to the setting of (1+1)-dimensional relativistic quantum field theories. This allows one to overcome the difficulties highlighted by Feynman concerning the application of the variational procedure to relativistic theories, and provides a new way to regularize quantum field theories. A fermionic version of the continuous matrix product state is introduced which is manifestly free of fermion doubling and sign problems. We illustrate the power of the formalism by studying the momentum occupation for free massive Dirac fermions and the chiral symmetry breaking in the Gross-Neveu model. 相似文献
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Tomáš Tyc Brett Hamilton Barry C. Sanders William D. Oliver 《Foundations of Physics》2007,37(7):1027-1048
Whereas boson coherent states with complex parametrization provide an elegant, and intuitive representation, there is no counterpart
for fermions using complex parametrization. However, a complex parametrization provides a valuable way to describe amplitude
and phase of a coherent beam. Thus we pose the question of whether a fermionic beam can be described, even approximately,
by a complex-parametrized coherent state and define, in a natural way, approximate complex-parametrized fermion coherent states.
Then we identify four appealing properties of boson coherent states (eigenstate of annihilation operator, displaced vacuum
state, preservation of product states under linear coupling, and factorization of correlators) and show that these approximate
complex fermion coherent states fail all four criteria. The inapplicability of complex parametrization supports the use of
Grassman algebras as an appropriate alternative.
相似文献
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G. E. Volovik 《Foundations of Physics》2003,33(2):349-368
Using quantum liquids one can simulate the behavior of the quantum vacuum in the presence of the event horizon. The condensed matter analogs demonstrate that in most cases the quantum vacuum resists formation of the horizon, and even if the horizon is formed different types of the vacuum instability develop, which are faster than the process of Hawking radiation. Nevertheless, it is possible to create the horizon on the quantum-liquid analog of the brane, where the vacuum life-time is long enough to consider the horizon as the quasistationary object. Using this analogy we calculate the Bekenstein entropy of the near-extremal and extremal black holes, which comes from the fermionic microstates in the region of the horizon—the fermion zero modes. We also discuss how the cancellation of the large cosmological constant follows from the thermodynamics of the vacuum. 相似文献