Causality in Quantum Teleportation

Quantum teleportation is a transfer protocol of unknown quantum state between two parties (Alice and Bob). This protocol includes two channels: quantum (maximum entangled state) and classic (standard communication channel). It turns out that the action of the quantum channel is solved to the transmission of information both forward and back in time. This leads to an occurrence of the phenomenon of conditional time travel, which was confirmed experimentally by a group Laforest in 2003. In the present study reverse-temporal processes from the perspective of quantum causal analysis, which is a new method that gives a formal definition and numerical measure of a causal relationship in an arbitrary two-part system are investigated. It is considered the modified Protocol teleportation without using additional classical channel. Instead of performing a unitary transformation Bob just makes the measurement over his particle. Time of the measurement of Bob was shifted in time, and then a change of causality was observed between the input condition, the result of a joint measurement of Alice and output result of Bob. It is established that the Bob’s result is always a consequence in relation to the first two values, even in case when it had been received till the making-ready moment of the input state. Thus, the reverse-temporal causality is received, but with the cause that contains absolutely random variable. Therefore, it can be argued that Bob receives a message from a random future. The use of causal analysis in the framework of the reverse-temporal approach to teleport what causes the introduction proper reading time for qubit during its teleportation (other than the reading time of the external observer), shows that in this reference frame all the effects are coming after the relevant causes. Besides demonstrating reverse-temporal causality, teleportation of a qubit being in a causal relationship with other qubit is considered. As a result the possibility teleportation of causality is showed.

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