Albert Einstein’s twin paradox is likely one of the most well-known thought experiments in physics. It postulates that when you ship considered one of two twins on a return journey to a star at close to gentle pace, they are going to be youthful than their similar sibling after they return residence. The age distinction is a consequence of one thing known as time dilation, which is described by Einstein’s particular concept of relativity: the quicker you journey, the slower time seems to move.
However what if we introduce quantum concept into the issue? Physicists Alexander Smith of Saint Anselm Faculty and Dartmouth Faculty and Mehdi Ahmadi of Santa Clara College sort out this concept in a research revealed as we speak within the journal Nature Communications. The scientists think about measuring a quantum atomic clock experiencing two different times whereas it’s positioned in superposition—a quirk of quantum mechanics through which one thing seems to exist in two locations directly. “We all know from Einstein’s particular concept of relativity that when a clock strikes relative to a different clock, the time proven on it slows down,” Smith says. “However quantum mechanics means that you can begin fascinated by what occurs if this clock have been to maneuver in a superposition of two completely different speeds.”
Superposition is a wierd facet of quantum physics the place an object can initially be in a number of areas concurrently, but when it’s noticed, solely a type of states turns into true. Particles will be positioned in superposition in sure experiments, comparable to these utilizing a beam splitter to divide photons of sunshine, to point out the phenomenon in motion. Each of the particles in superposition seem to share data till they’re noticed, making the phenomenon helpful for functions comparable to encryption and quantum communications.
Some atoms, in the meantime, can act as atomic clocks, with their charge of decay noting the passage of time. Of their paper, Smith and Ahmadi describe how an atomic clock positioned in superposition might expertise time dilation, similar to Einstein’s twins experiment, if one of many superposition states is moved at a number of meters per second whereas the opposite stays stationary. As a substitute of the atom merely being in two states directly—as described within the Schrödinger’s cat experiment—the states would truly age in another way. “It’s type of like ‘Schrödinger’s clock,’” Smith says.
Vlatko Vedral, a physicist on the College of Oxford, who was not concerned within the research, says the thought permits for a uncommon alternative to merge quantum mechanics with relativity—two areas of physics that infamously don’t combine nicely. “You may truly mix the superposition precept in quantum mechanics with this notion of time dilation in relativity,” he says. “It’s precisely Einstein’s twins however now utilized to the identical system. That’s the twist. The ultimate state is actually superb, as a result of the atom is again in the identical place the place you began, however internally, it feels two completely different occasions. It’s in a superposition of being older and youthful on the identical time.”
Although the impact is much too small to be noticeable to people, this concept of quantum time dilation might have repercussions for high-precision quantum clocks. And crucially, the brand new research suggests it may be doable to measure the impact experimentally. “I’m hoping this paper actually prompts folks to strive to do that within the lab,” Vedral says. And Smith suggests an experimental proposal may very well be drafted within the close to future, maybe utilizing spectroscopy to separate gentle, to search for this signature of quantum time dilation. “We’d have the ability to see this within the subsequent 5 to 10 years,” he says. “I don’t suppose it’s science fiction by any means.”