Physicists convinced particles of light simultaneously undergo opposite transformations, just as humans turn into werewolves when werewolves transform into humans. In carefully designed circuits, photons behave as if time were flowing in a combination of forward and backward quanta.
“For the first time, we have a time travel machine going in both directions,” said Sonja Franke-Arnolda quantum physicist at the University of Glasgow in Scotland who was not involved in the study.
Unfortunately for science fiction fans, these devices have nothing in common with 1982’s DeLorean. During experiments conducted by two independent groups in China and Austria, the clocks were in the lab. continue to run steadily. Only photons passing through the circuit undergo temporary mischief. And even for photons, the researchers debate whether the rotation of the arrow of time is real or simulated.
Either way, the phenomenon of confusion could lead to new types of quantum technologies.
“You can envision circuits where your information can flow both ways,” says Giulia Rubinoa researcher at the University of Bristol.
Anything anytime all at once
A decade ago, physicists first realized that the strange laws of quantum mechanics overturn conventional notions of time.
The essence of quantum weirdness is this: When you look for a particle, you will always discover it in a single location, like a point. But before being measured, a particle behaves more like a wave; it has a “wave function” that spreads and ripples over many routes. In this unknown state, a particle that exists in a quantum mixture of positions can be called pile.
IN a piece of paper published in 2013, Giulio Chiribella, a physicist now at the University of Hong Kong, and co-authors have proposed an electrical circuit that could bring events into a superposition of temporal orders, far beyond the superposition of position in one-step space. Four years later, Rubino and her colleague Experiment to prove it directly Idea. They send a photon down by a superposition of two paths: one in which it goes through event A then event B, and another path through which it goes through B then A. In a sense, each the event that seems to cause the other event, a phenomenon has occurred. call cause and effect unknown.
Not content with merely disturbing the order of events as time moves forward, Chiribella and a colleague, Zixuan Liu, next aim for the direction of movement, or arrow, of time itself. They look for a quantum device in which time enters a superposition that flows from the past to the future and back—an indefinite arrow of time.
To do this, Chiribella and Liu realized they needed a system that could undergo the opposite changes, like a metronome whose arm could swing left or right. They imagine placing such a system in a superposition, like a musician flipping a quantum metronome to the right and left at the same time. Surname describe a plan to establish such a system by 2020.
Optical magicians immediately began building duel arrows of time in the lab. Last fall, the two teams declared success.
Game twice
Chiribella and Liu have devised a game that only a double quantum timer can outperform. Playing a game with light involves shooting photons through two crystal gadgets, A and B. Forward propagation through a gadget rotates the photon’s polarization by an amount depending on the settings of the light. utilities. Going backward through the utility rotates the polarity in the opposite way.
Before each round of the game, a secret referee places the devices in one of two ways: The path goes to A, then back through B, or will shift the photon’s wavefunction relative to the path back in time. (go back through A, then forward through B), or it won’t. The player must find out the choice the referee makes. After the player arranges the gadgets and other optical components the way they want, they send a photon through the maze, which can be split into a superposition of two paths using half mirrors. silver. The photon ends up at one of the two detectors. If the player has set up their maze intelligently enough, a click on the photon detector will reveal the referee’s choice.
