The quantum world operates by different rules than the classical one we buzz around in, allowing the fantastical to the bizarrely normal. Now, a team of physicists has used quantum entanglement to simulate a closed timelike curve—in layman’s terms, time travel.
Before we proceed, I’ll stress that this was simulated; no quantum particles went back in time. The research was a Gedankenexperiment, a term popularized by Einstein to describe conceptual studies conducted in lieu of real tests—a useful thing when one is testing physics at its limits, like particles moving at the speed of light. But “effective time travel” was achieved in the simulation, according to the team’s recent paper in Physical Review Letters, thanks to a famously strange way that quantum particles can interact.
That interaction is called quantum entanglement, and it describes when the characteristics of two or more quantum particles are defined by each other. This means that knowing the properties of one entangled particle gives you information about the other, regardless of the distance between the two particles; their entanglement is on a quantum level, so a little thing like their physical distance has no bearing on the relationship. Space is big and time is relative, so a change to a quantum particle on Earth that’s entangled with a particle near a black hole 10 billion light-years away would mean changing the behavior of something in the distant past.
The recent research explores the possibility of closed-timelike curves, or CTCs—a hypothetical pathway back in time. The curve is a worldline—the arc of a particle in spacetime over the course of its existence—that runs backwards. Steven Hawking posited in his 1992 “Chronology protection conjecture” paper that the laws of physics don’t allow for closed timelike curves to exist—thus, that time travel is impossible. “Nevertheless,” the recent study authors wrote, “they can be simulated probabilistically by quantum-teleportation circuits.”
PERCEPTION RESET 