"Time Travel" clickbait

I won't link the clickbait sites that claimed that physicists had reversed time, against the laws of physics.

A better story is here. You know that billiard balls bouncing off each other would look the same if time were reversed, but a video of a dropped egg would look exceedingly strange. The reason has to do with entropy, and the dissipation of structure.

If you take a particle whose position and momentum are known as well as they can be (Heisenberg Uncertainty forbids both being known simultaneously), and let it evolve over time, the waveform describing it will smear out over time. Is that the same thing as the dissipation of structure you get with an egg? Not really, but it looks kind of like it.

They modeled this quantum-mechanical state with quantum-mechanical q-bits.

Instead of an electron, they observed the state of a quantum computer made of two and later three basic elements called superconducting qubits.

The researchers found that in 85 percent of the cases the two-qubit quantum computer indeed returned back into the initial 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.

Or in other words, they modeled the system with something which they were able to reverse (most of the time), just as though time were reversed. Except, of course, that time wasn't reversed, just the structure of the system.

I don't know how the rest of the community is taking this, but it doesn't seem like a surprise to me. The smearing of such a simple system seems very much like a quantum-mechanical analog of those billiards--just the sort of simple thing that could be reversible. I haven't read the paper, so I'm taking them at their word--and it sounds clever. But no, it isn't time reversal.