The strange phenomenon of quantum entanglement, in theory, can span not only space but also time. And then it becomes really confusing.
Quantum entanglement (otherwise - confusion) may well be called one of the most famous and most incomprehensible from the point of view of everyday logic of the effects of the microworld. It consists in the fact that the states of two (or even more) quantum objects appear to be connected, regardless of the distance between them, - the impact on one of them instantly (in the literal sense of the word) affects the other object linked to it. It is known that Einstein had difficulty accepting such phenomena, and called entanglement "nightmare action at a distance." But it looks like the real nightmare is just beginning.
Recently, Australian researchers from Professor Timothy Ralph's group looked at quantum entanglement of a slightly different nature - one that extends not through space, but through time - and here everything looks even more confusing. Let's try to understand their constructions.
Scientists begin their thinking with a simplified picture of the universe, consisting of one spatial and one temporal dimensions. It is quite easy to depict it on a plane: we will correlate the ordinate axis with space, and the abscissa axis with time. We place the current moment at the origin; the future will be located to the right of the ordinate axis, the past - to the left. The probable positions of a particle in the future (and in the past) can be thought of as symmetrical mountains that grow with distance from the present. If we add similar “mountains” for another particle, they partially overlap each other in the past and in the future. This means that both in the past and in the future there is a probability of meeting of both particles and, as a consequence, their interaction with each other - precisely in the areas of overlap.
Ordinary quantum entanglement, according to the authors, in this picture corresponds to an instantaneous vertical slice passing through the region of overlapping probability functions of particles. But with the same success - they note - the cut can be made horizontally, parallel to the time axis!
What can this lead to? To completely surprising conclusions. For example, to the fact that a measurement taken in the past is directly related to the future. Say, nothing surprising? Not really: it’s not just a simple causal relationship.
To clarify the strangeness of the situation, Ralph and his colleagues propose such a thought experiment. Imagine that a qubit is created with certain parameters and travels to the future. Having certain parameters means having the classic description of this qubit. Then, at some distance in the future, another detector located at the same point in space receives this description, thereby "reconstructing" the original qubit. According to scientists, if a qubit is detected at a point in the future, symmetrical to the moment of its creation, it can be called "entanglement in time" - or even "teleportation in time." The material particle itself may not exist in the interval between these symmetrical moments, as if instantly displaced from one to another. Just jumping in time.
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