An international team of scientists led by researchers at the Moscow Institute of Physics and Technology demonstrated the possibility of time reversal in a development that contradicts the basic laws of physics, Newsweek reported on Wednesday. The researchers were assisted by colleagues in Switzerland and the United States.
Lead researcher Dr Gordey Lesovik, who heads the Laboratory of the Physics of Quantum Information at the Moscow Institute of Physics and Technology, said, “We have artificially created a state that evolves in a direction opposite to that of the thermodynamic arrow of time.”
The thermodynamic arrow of time refers to the Second Law of Thermodynamics, which states that “disorder” only increases with time, and can never decrease. A direction opposite to this, previously unknown, would mean that the object moves back from a state of chaos to order.
In a study published in the journal Scientific Reports on March 13, the scientists experimentally showcased time reversal by sending a qubit from a more complex state to a simpler one using an algorithm on an IBM quantum computer. A qubit, or quantum bit, is the basic unit of quantum information. It is the quantum version of a computer binary bit, which can be a one or a zero.
The quantum physicists decided to check if time could spontaneously reverse itself, at least for an individual particle, and for a tiny fraction of a second. As a result, they examined a single electron in empty interstellar space.
“Suppose the electron is localised when we begin observing it. This means that we are pretty sure about its position in space,” said the study’s co-author Andrey Lebedev from the Moscow Institute of Physics and Technology. “The laws of quantum mechanics prevent us from knowing it with absolute precision, but we can outline a small region where the electron is localised.”
The researchers attempted to calculate the probability of observing an electron over a fraction of a second spontaneously localising into its recent past. Later, they made the same attempt to reverse time using qubits. They employed a programme to convert the qubits into a more complex pattern of ones and zeros, and then used another programme to bring them back to their original state. This successfully caused the qubits to evolve backwards, from chaos towards order.
The team found that in 85% of the cases, the two-qubit quantum computer returned back to the initial state. However, more errors occurred when a third qubit was introduced, with the success rate falling to around 50%.
“Such an unfortunate growth of the complexity explains why do we not observe such time-reversed objects in nature,” said Lebedev. “The probability of a spontaneous appearance of a time-reversed object [particle of a system of particles] is negligible.”