According to a new study, time, which has long been considered a basic aspect of our cosmos, may actually be an illusion caused by quantum entanglement.
This concept offers a new viewpoint on a long-standing problem for physicists: the inconsistency of time in our best theories of the cosmos, which impedes the search for a unified “theory of everything.”
Researchers argue that time is caused by quantum entanglement, the inexplicable connection between particles separated by great distances. Their discoveries, which were published in the journal Physical Review A, could help solve the time conundrum.
“There is a way to introduce time that is consistent with both classical and quantum laws, and is a manifestation of entanglement,” noted Alessandro Coppo, a physicist at the National Research Council of Italy and the study’s primary author. “The correlation between the clock and the system creates the emergence of time, a fundamental ingredient in our lives.”
In quantum mechanics, time is a constant flow from past to present. It stays apart from the ever-changing quantum systems it measures and can only be observed through changes in external things, such as the hands of the clock.
In contrast, Einstein’s theory of general relativity, which deals with larger objects such as stars and galaxies, describes time as entwined with space, capable of warping and dilation under high speeds or strong gravitational fields. This disagreement causes a considerable contradiction between our two greatest explanations of reality, impeding the development of a coherent theory of everything.
“It seems there is a serious inconsistency in quantum theory,” Coppo told reporters. “This is what we call the problem of time.”
To solve this, the researchers examined the Page and Wootters mechanism, which was proposed in 1983. It implies that time emerges from quantum entanglement between one item and another, which serves as a clock. In an unentangled system, time does not exist, and the universe appears static and unchanging.
The researchers discovered that their system was in perfect agreement with the Schrödinger equation, which describes the behavior of quantum objects, when they applied this mechanism to two entangled but noninteracting theoretical quantum states: a vibrating harmonic oscillator and a collection of small magnets functioning as a clock. Their version of the equation operated based on the states of the small magnets rather than conventional time.
Although this idea isn’t wholly original, the team’s subsequent action was revolutionary. They made the same calculations again, assuming that the harmonic oscillator and the magnet clock were macroscopic objects. The equations were reduced to those of classical physics, indicating that even at huge scales, entanglement is responsible for the flow of time.
“We strongly believe that the correct and logical direction is to start from quantum physics and understand how to reach classical physics, not the other way around,” according to Coppo.
Despite the intriguing potential, several physicists advise caution. They find the Page and Wootters technique fascinating, but it has yet to provide testable findings.
“Yes, it is mathematically consistent to think of universal time as the entanglement between quantum fields and quantum states of 3D space,” said Vlatko Vedral, a professor of quantum information science at the University of Oxford who was not involved in the study. “However, no one knows if 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 reservations, developing time theories based on quantum mechanics may still be a worthwhile strategy, if they can be proven experimentally.
“Maybe there is something about entanglement where it plays a role,” said Adam Frank, a theoretical physicist at the University of Rochester in New York who was not involved in the work. “Maybe the only way to understand time is not from some God’s-eye perspective, but from the inside, from a perspective of asking what is it about life that manifests such an appearance of the world.”
This new view on time as an emergent characteristic of quantum entanglement might lead to new ways of interpreting the cosmos.
To bridge the gap between quantum mechanics and general relativity, these theories must be developed in experimentally testable ways.
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