QUANTUM CAUSALITY
QUANTUM CAUSALITY
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DOI：
10.1142/9789814504782_0031
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
Peter J. Riggs;Peter J. Riggs
中科院分区：
文献类型：
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作者：
Peter J. Riggs;Peter J. Riggs
因果分析的量子扩展展示了子系统因果关系的丰富图景，而通常的直观方法更容易受到阻碍。因果连接的方向由不可逆信息流的方向决定，并且这种连接的度量（称为时间过程 2 c ）被确定为这种流的速度。不存在因果关系对应于 2 | | c ，因此因果关系的程度与 2 c 成反比。这种因果关系的正式定义在任何时间方向都是有效的。因果分析的可能性之前已经通过一系列二量子位和三量子位状态的例子得到了证明。在本文中，我们考虑新的应用程序。第一个是将量子因果分析应用于退相干下的不对称纠缠态。研究了三种退相干模型：耗散、去极化和去相位。对于所有模型，已计算了诱发因果关系的强度和方向。事实证明，沿着原始因果关系作用的退相干对纠缠的破坏程度比反对这种因果关系的退相干程度要小。第二个应用是通过 Jaynes-Cummings 模型研究二能级原子与场的无限维量子化模式之间的相互作用。研究了不同初始状态下冯诺依曼方程的解析解。场最初被认为处于热混合态，而原子依次处于激发态、基态或热态。计算不同温度的负性、互信息和因果特征。结果表明，在高温下，不同初始状态的行为之间的区别会变得平滑，并且状态在熵意义上是因果的、纠缠的和“经典的”。第三个应用是隐形传态（三粒子协议）。本质上，传送的量子位并不是原始量子位的效果；它证明了另外两个的共同作用。但与此同时，贝尔测量的结果从纠缠对的每个量子比特诞生的那一刻起就构成了原因。后者是因果关系在逆时间上的体现。
The quantum extension of causal analysis has shown a rich picture of the subsystem causal connections, where the usual intuitive approach is hampered more commonly. The direction of causal connection is determined by the direction of irreversible information flow, and the measure of this connection, called the course of time 2 c , is determined as the velocity of such flow. The absence of causality corresponds to 2 | | c , accordingly the degree of causal connection is inversely related to 2 c . This formal definition of causality is valid at any time direction. The possibilities of causal analysis have been demonstrated before by series of examples of the twoand three-qubit states. In this paper we consider the new applications. The first one is the application of quantum causal analysis to the asymmetric entangled state under decoherence. Three models of decoherence: dissipation, depolarization and dephasing are studied. For the all models the strength and the direction of induced causality has been computed. It turns out that the decoherence acting along original causality destroys entanglement to a lesser degree than it acting against this causality. The second application is the interaction between a two-level atom and infinite-dimensional quantized mode of a field by Jaynes-Cummings model. An analytical solution of von Neumann equation for different initial states is examined. The filed is considered initially to be in thermal mixed state, while atom – sequentially in excited, ground or thermal states. Negativity, mutual information and causal characteristics for different temperatures are computed. It is obtained that for high temperatures distinction between behaviors of different initial states smoothes over and the state turns out to be causal, entangled and “classical” in entropic sense. And the third application is the teleportation (three-particle protocol). Contrintuitively the teleported qubit is not an effect of the original one; it proves the common effect of both two other ones. But at the same time the result of Bell measurement constitutes a cause with respect to every qubits of entangled pair just since moment of their birth. The latter is manifestation of causality in reverse time.