How Time Turns (and What Doesn’t) Quantum Physicists

Physicists have convinced Light particles undergo opposite transformations simultaneously, such as the transformation of a human into a werewolf where a wolf turns into a human. In a carefully designed circuit, photons act as if time is flowing in a quantum mix of forward and backward.

“For the first time, we have a time travel machine that goes both ways,” he said. Sonya Frank Arnolda quantum physicist at the University of Glasgow in Scotland who was not involved in the research.

Unfortunately for sci-fi fans, the hardware bears little in common with a 1982 DeLorean. Throughout the experiment, conducted by two independent teams in China and Austria, the lab’s clock kept ticking. Only the photons flowing through the circuit are time-rigged. Even for photons, researchers debate whether reversing the arrow of time is real or simulated.

Either way, this puzzling phenomenon could lead to a new kind of quantum technology.

“You can visualize a circle where your information can flow in both directions,” he says. Julia RubyResearcher at the University of Bristol.

anything anytime at once

Physicists first realized a decade ago that the strange rules of quantum mechanics overturned the logical notion of time.

The essence of the quantum oddity is this: When you look for a particle, you will always find it in one point-like location. But before they can be measured, the particles behave like waves. It has a “wave function” that propagates and ripples through many paths. In this indeterminate state, the particle exists in a quantum collection of possible sites known as a overlap.

inside paper published in 2013, Julio Chiribella, a physicist now at the University of Hong Kong, the co-authors proposed a circuit that would place events into a superposition of temporal orders, bypassing the step of superimposing locations in space. Four years later, Rubino and co empirically direct Idea. They send the photons through a superposition of two paths: one in which event A encounters event B then event B, and another in which event B encounters then A. In a sense, each event seems to cause the other, a phenomenon that has come to be called Unspecified cause.

Not content with simply tweaking the order of events as time went on, Chiribella and her partner Zexuan Liu took aim at the march, or arrow, for time itself. They are looking for a quantum device in which time enters into a superposition flowing from the past to the future and back—the infinite arrows of time.

To do this, Chiribella and Liu realized they needed a system that could change in opposite directions, such as a metronome that could swing its arm left or right. They envision placing such systems in a superposition, akin to a musician moving a quantum accelerator simultaneously left and right. they Schematic description To build such a system by 2020.

The optics wizard immediately started making dueling arrows for his time in the lab. Last fall, two teams reported success.

Double game

Chiribella and Liu come up with a game that only a two-quantum timer can beat. Playing the game with light involves shooting a photon through two crystal tools, A and B. Passing it through the tools rotates the photon’s polarization by an amount that depends on the device settings. Passing backwards through the instrument rotates the polarization exactly in the opposite direction.

Before each round of play, the referee discreetly adjusts the instrument in one of two ways: a path forward through A, then backward through B, will shift the photon’s wavefunction relative to the reverse time path (backward through A, then forward through B), or won’t do it. Players must know the choices made by the referee. Once players have arranged tools and other visual elements the way they want, they send photons through the maze, perhaps splitting it into two-lane superpositions using half-silver mirrors. The photons end up in one of the two detectors. If the player manages his maze in a smart enough way, a flick of the photon-filled detector will reveal the judge’s choice.