Time Moves Forward Even In The Quantum World

 

Researchers have proven that the laws of thermodynamics work in the quantum world. This discovery has vast implications for technologies currently being developed, like quantum computers.

 

Physicists created an experiment in which they revealed the irreversibility of a quantum mechanical process. They formed an isolated quantum system and calculated the change in entropy – defined as a gradual decline into disorder – when applying an oscillating magnetic field. If the system was reversible, the entropy wouldn’t increase and move towards disorder, but in reality it does.

 

We don’t know why time passes. We think that the arrow of time has a direction as a result of second law of thermodynamics. The law says that the entropy of the universe always increases, with the entropy being the level of disorder of a system. Principally, the second law states that you can’t perfectly put back together a broken vase. If we see a broken vase, we know that it was broken in the past.

 

Quantum mechanics has thus far avoided being affected by thermodynamics. Most of the quantum laws are flawlessly symmetric in time. “Quantum vases” break apart and jump back together and both scenarios are perfectly allowed. But this experiment revealed that thermodynamics affects the quantum world as well and that the arrow of time ascends naturally from the fundamental laws of the universe.

 

In the experiment, the researchers measured the entropy of a sample of liquid chloroform. It is useful because the spin of the nucleus of the hydrogen atom couples with the spin of the nucleus of the carbon atom. A flexible magnetic field was applied to the system, and whenever the magnetic field would reverse, the spin would flip.

 

The changes in the magnetic field were so quick that the spins stopped keeping up with it and they stopped being in equilibrium, letting the entropy of the system increase.

 

The physicists think that the lack of equilibrium arises directly from the early condition of the system. The laws of quantum mechanics always start with systems in perfect equilibrium, but generating such a system in reality is very difficult and all the processes we have detected so far are not truly in equilibrium. "Full and perfect reversibility is an idea that might be approximately achieved in very controlled situations," Mauro Paternostro, co-author of the research, told IFLScience.

 

References:

Physical Reviews Letter, Science Alert