Time is one of the great mysteries of the universe.
New research led by the University of Bristol (UK) suggests that the flow of time at the quantum level does not have to go in only one direction. Quantum systems, under certain conditions, can go back and forth in time.
What if the arrow of time observed phenomena in which the entropy changes are small?
This was the starting point of the research published in the journal Communications Physics.
“Let’s take the case of a gas in a container,” explains Giulia Rubino, from the University of Bristol and lead author of the study. “Suppose that at the beginning, the gas occupies only half of the container. Then imagine that we removed the valve that was confining it within the middle of the container, so that the gas can now expand freely throughout the container ”.
The particles will begin to move freely throughout the volume of the container. Over time, the gas will fill the entire container.
“In principle, there is a nonzero probability that at some point the gas will naturally reoccupy half the container, only this probability becomes less the greater the number of particles that make up the gas,” says Rubino.
If there were only three gas particles instead of a huge amount of gas, it would be possible for these few particles to end up once more in the part of the container from which they originally started.
Entropy spontaneously decreasing.
“Although time is often treated as a continuously increasing parameter, our study shows that the laws governing its flow in quantum mechanical contexts are much more complex. This may suggest that we need to rethink the way we represent this quantity in all those contexts where quantum laws play a crucial role ”, concludes Rubino.
Referencia: Giulia Rubino, Gonzalo Manzano, Časlav Brukner. Quantum superposition of thermodynamic evolutions with opposing time’s arrows. Communications Physics, 2021; 4 (1) DOI: 10.1038/s42005-021-00759-1
