A study published on May 10th in the journal Physical Review A revealed that time comes from quantum entanglement, a weird connection between two distinct particles. A perspective on one of the most fundamental aspects of the universe- time was presented in the research. According to the research, time may not be a real entity but an illusion generated by quantum physics.

The Nature of Time in Quantum Mechanics

Time has been a challenging concept to define in physics due to its inconsistent behaviour when examined through the lens of the two leading theories of the universe. They are quantum mechanics and general relativity. This inconsistency has often resulted in dead ends, stopping scientists from formulating a unified "theory of everything" that explains all physical phenomena in the universe. The new study, however, offers a solution to this problem.

"There exists a way to introduce time which is consistent with both classical laws and quantum laws and is a manifestation of entanglement," said Alessandro Coppo, a physicist at the National Research Council of Italy and the study's first author, in an interview with Live Science.

Quantum Entanglement
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The two prevailing theories on time present are fundamentally different in views. In quantum mechanics, time is perceived as a fixed phenomenon with a unidirectional flow from the past to the present. It remains external to the ever-changing quantum systems it measures and can be observed only through changes in external entities, such as the hands of a clock.

Whereas, Einstein's theory of general relativity suggests that time is interwoven with space, forming a four-dimensional fabric known as spacetime. This spacetime can be warped and dilated under the influence of high speeds or strong gravitational fields. This difference between the two theories has caused challenges for physicists attempting to combine them.

"It seems there is a serious inconsistency in quantum theory," Coppo added. "This is what we call the problem of time."

To solve this issue, the researchers suggested a theory known as the Page and Wootters mechanism, first proposed in 1983. This theory says that time emerges for one object through its quantum entanglement with another object, which acts as a clock. In the absence of such entanglement, time does not exist for the system, and the universe appears frozen.

The researchers applied this theory to two entangled but non-interacting theoretical quantum states. It included a vibrating harmonic oscillator and a set of tiny magnets functioning as a clock. They discovered that their system could be accurately described by the Schrödinger equation, an equation in quantum mechanics. The researchers repeated their calculations, assuming first that the magnet clock and then the harmonic oscillator were macroscopic objects. Their equations are simplified, showing that the flow of time is a consequence of entanglement, even for objects on larger scales.

"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," Coppo emphasised.

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