Fantasy works teach us not to interfere in the course of history if we suddenly happened to be in the past. Perhaps for classical physics the “butterfly effect” rule really works, but in the case of quantum physics, reality is surprisingly more stable.
In classic fiction, time travelers must obey the important rule of not making even minor changes in the past so as not to cause the "butterfly effect" - an avalanche of unpredictable changes that lead to catastrophic consequences: the present can be completely different, and your parents never meet.
However, the laws of quantum mechanics are not as harsh as scientists from the Los Alamos National Laboratory (USA) proved using a quantum computer, writes Science Daily.
Using an IBM-Q quantum processor, a team of scientists created a complex system using a quantum gate and demonstrated cause and effect by running it back and forth in time. The model included two hypothetical subjects, Alice and Bob, who each had a qubit - a quantum bit of information.
In this scenario, Alice is sending her qubit back from the present. At this point, Bob interacted with this qubit, measuring it. Then he sent a message to the future, where Alice tested the qubit.
If the rules of the "butterfly effect" were true for the quantum world, then Bob's slight impact on a qubit associated with so many variables should completely change the system in the present. However, this did not happen. Alice's qubit returned relatively unscathed, and she was able to recover the information he was carrying. Curiously, it was a large number of variables that actually saved it from damage - information in the qubit's present was hidden in quantum correlations deep in the past. This network of connections is not easy to destroy.
“We found that the concept of chaos in classical physics and in quantum mechanics should be understood in different ways,” explained Sinitsyn.
The experiment has practical value. First, since a classical processor cannot do this kind of simulation, it can be used to test whether a quantum computer actually operates on quantum principles. Second, the results can be used to create new information security protocols in quantum systems.
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IBM first unveiled a quantum computer for commercial use at last year's CES in Las Vegas. A glass capsule with a 20 qubit processor can be rented temporarily through the cloud service.