New research suggests that time may not be a fundamental element of the universe, but rather an illusion created by quantum entanglement.
Time is a difficult problem for physicists; the inconsistent behavior of our best theories of the universe contributes to a stalemate that leaves researchers unable to find a “theory of everything,” or a framework to explain all of the physics in the universe.
But in the new study, researchers suggest they may have found a clue to solving that problem: by making time a consequence of quantum entanglementthe strange connection between two widely separated particles. The team published their findings May 10 in the journal Physical assessment A.
“There is a way to introduce time that is consistent with both classical and quantum laws, and is a manifestation of entanglement,” the first author said. Allesandro Coppoa physicist at Italy’s National Research Council, told Live Science. “The correlation between the clock and the system creates the emergence of time, a fundamental ingredient in our lives.”
It’s about time
In quantum mechanicsour best theory of the microscopic world, time is a fixed phenomenon — an inexorable, unidirectional flow from the past to the present. It remains external to the bizarre and ever-changing quantum systems it measures, and can only be seen by observing changes in external entities, like the hands of a clock.
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However, according to Einstein’s theory, it is true that general theory of relativity —which describes larger objects, such as our bodies, stars, and galaxies—time is intertwined with space and can be warped and stretched at high speeds or in the presence of gravity. This brings our two best theories of reality to a fundamental impasse. Without its resolution, a coherent theory of everything remains out of reach.
“It looks like there’s a serious inconsistency in quantum theory,” Coppo said. “This is what we call the problem of time.”
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 is created for one object by its quantum entanglement with another acting as a clock. For an inextricable system, on the other hand, time does not exist, and the system perceives the universe as frozen and unchanging.
By applying the Page and Wootters mechanism to two entangled but non-interacting theoretical quantum states — one a vibrating harmonic oscillator and the other a set of tiny magnets acting as a clock — the physicists found that their system could be perfectly described by the Schrödinger equationthat predicts the behavior of quantum objects. But instead of time, their version of the famous equation ran according to the states of the tiny magnets that acted as 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 for classical physics, suggesting that the flow of time is a consequence of entanglement, even for large-scale objects.
“We believe that the right and logical direction is to start from quantum physics and understand how to get to classical physics, and not the other way around,” Coppo said.
Other physicists have been cautious. Despite finding Page and Wootter’s mechanism a fascinating idea for the quantum origin of time, they say it has not yet yielded anything testable.
“Yes, it is mathematically consistent to consider universal time as the entanglement between quantum fields and quantum states of 3D space,” Flat Vedrala professor of quantum information science at the University of Oxford who was not involved in the work, told Live Science. “But no one knows whether anything new or fruitful will come out of this picture — such as tweaks to quantum physics and general relativity, and corresponding experimental tests.”
Despite these doubts, building theories of time from quantum mechanics may still be a promising place to start, as long as they can be designed in such a way that they are amenable to experiment.
“Perhaps entanglement does play a role,” Adam Franka theoretical physicist at the University of Rochester in New York who was not involved in the study, told Live Science. “Perhaps the only way to understand time is not from some divine perspective, but from the inside, from a perspective of asking what it is about life that manifests such an appearance of the world.”