Time traveling robots
Emailed on March 15, 2019 in The Friday Forward
Researchers from the Moscow Institute of Physics and Technology teamed up with colleagues from the U.S. and Switzerland and returned the state of a quantum computer a fraction of a second into the past.
So, like, they went back in time.
"This is one in a series of papers on the possibility of violating the second law of thermodynamics. That law is closely related to the notion of the arrow of time that posits the one-way direction of time from the past to the future," said the study's lead author Gordey Lesovik, who heads the Laboratory of the Physics of Quantum Information Technology at MIPT.
The article from Phys Org gets a little heady, so here's my very elementary explanation for what these folks did.
The analogy used in the article is to imagine a billiard's cue ball breaking up a pyramid of other billiard balls. The billiard balls breaking apart is analogous to the way an electron, according to the second law of thermodynamics, either remains static or evolves toward a state of chaos rather than order (like when the billiard balls break apart).
The physicist explains that the evolution of the electron state is governed by Schrödinger's equation. Although it makes no distinction between the future and the past, the area containing the electron (like the triangle area the billiard balls are in) will spread out very quickly. That is, the system tends to become more chaotic.
The crux of the experiment was to prove that Schrödinger's equation could be reversed.
Imagine that after the billiard balls are broken, someone gave a perfectly calculated kick to the table that returned all the balls exactly to their original organization (the pyramid).
The billiard balls, in this experiment, were actually qubits in a quantum computer. In the first stage, each qubit is in its ground state. In the second, the qubits begin to change patterns (combinations of either 1 or 0). In the third, the researchers introduce a program that "kicks" the qubits. In the fourth stage, the qubits return to their ground state (like the pyramid of billiard balls).
The researchers found that in 85 percent of the cases, the two-qubit quantum computer returned back into the initial ground state. When three qubits were involved, more errors happened, resulting in a roughly 50 percent success rate. According to the authors, these errors are due to imperfections in the actual quantum computer, but that using the time reversal algorithm, they could make quantum computers more precise.
Which I have interpreted to mean the computers are going to teach themselves to time travel. Do with this information what you'd like.