Time may not be a fundamental element of the universe, but rather an illusion arising from quantum entanglement, a new study suggests.
time is a thorny problem for physicists; its inconsistent behavior among our best theories of the universe contributes to the impasse that prevents researchers from finding a “theory of everything,” or a framework to explain all the physics in the universe.
But in the new study, researchers suggest they may have found a key to solving this problem: by making time a consequence of quantum entanglement, the strange relationship between two distant particles. The team published their findings May 10 in the journal Physical examination A.
“There is a way to introduce time that is consistent with both classical and quantum laws and is a manifestation of entanglement,” first author Alessandro Coppo, a physicist at Italy’s National Research Council, told Live Science. “The correlation between the clock and the system creates the appearance of time, an essential ingredient in our lives.”
It is time
in quantum mechanics, our best theory of the microscopic world, time is a fixed phenomenon—an inexorable, one-way flow from the past to the present. It remains external to the strange and ever-changing quantum systems it measures, and can only be seen by observing changes in external objects, such as the hands of a clock.
Connected: Atoms collided closer together than ever before, revealing seemingly impossible quantum effects
Yet, according to Einstein’s theory of general relativity — which describes larger objects, such as our bodies, stars and galaxies — time is intertwined with space and can be warped and expanded at high speeds or in the presence of gravity. This leaves our two best theories of reality at a fundamental impasse. Without its resolution, a coherent theory of everything remains out of reach.
“There seems to be a serious inconsistency in quantum theory,” Coppo said. “This is what we call the timing problem.”
To solve this problem, the researchers turned to a theory called the Page and Wootters mechanism. First proposed in 1983, the theory suggests that time arises for an object through its quantum entanglement with another acting as a clock. For an unentangled system, on the other hand, time does not exist and the system perceives the universe as frozen and unchanging.
By applying Page and Wootters’ mechanism to two entangled but noninteracting theoretical quantum states—one a vibrating harmonic oscillator and the other a set of tiny magnets acting like a clock—the physicists found that their system could be perfectly described by Schrödinger equation, which predicts the behavior of quantum objects. Yet, instead of time, their version of the famous equation moved according to the states of tiny magnets acting like a clock.
This insight isn’t new, but the team’s next step was. They repeated their calculations twice, first assuming that the magnetic clock and then the harmonic oscillator were macroscopic (larger) objects. Their equations simplified to those of classical physics, suggesting that the flow of time is a consequence of entanglement even for objects on large scales.
“We strongly believe that the right and logical direction is to start from quantum physics and figure out how to get to classical physics, not the other way around,” Coppo said.
Other physicists expressed caution. Although Page and Wootters find the mechanism a fascinating idea about the quantum origins of time, they said it has not yet yielded anything that can be verified.
“Yes, it is mathematically consistent to think of universal time as an entanglement between quantum fields and quantum states of 3D space,” Vlatko Vedral, a professor of quantum information science at Oxford University who was not involved in the work, told Live Science. “However, no one knows whether anything new or fruitful will come out of this picture—such as modifications to quantum physics and general relativity and corresponding experimental tests.”
Despite these misgivings, building fundamental theories of time from quantum mechanics may still be a promising place to start—as long as they can be shaped to fit experiments.
“Maybe there’s something about entanglement where it plays a role,” Adam Frank, a theoretical physicist at the University of Rochester in New York who was not involved in the research, told Live Science. “Perhaps the only way to understand time is not from some God’s-eye perspective, but from within, from the perspective of asking what it is about life that manifests this kind of world.”
