A New Test of Einstein’s Theory of Relativity
August 18, 2015
The Jerusalem Post — Although logically it’s impossible to put one object in two different places at the same time, a team of BGU researchers have managed to put a clock in two locations simultaneously.
Led by Prof. Ron Folman, head of BGU’s Atom Chip Lab, a quantum physicist, and a member of BGU’s Ilse Katz Institute for Nanoscale Science and Technology, the group’s study was recently published in the prestigious scientific journal, Science.
The researchers describe how their findings will facilitate the study of the role of time in the dynamics of the universe and could provide better understanding of the connection between Albert Einstein’s theory of general relativity and quantum mechanics.
These two theories constitute the physics revolutions of the 20th century, and many attempts have been made to unify them or – at the very least – understand how they work together.
“We demonstrate a new tool for investigating time in the overlap of these two theories – a self-interfering clock, comprising two atomic spin states,” they stated.
The BGU researchers took an atom and turned it into an atomic clock – like those used in many technological zero applications such as global positioning systems (GPS). At the same time, they transferred the atom through a device capable of positioning it in two places simultaneously.
This device, called an interferometer, works according to the laws of quantum mechanics, which enable an object to be in several places at once. According to standard quantum mechanics, time “ticks” at the same speed all over the universe.
In Einstein’s theory of general relativity (which he proposed in 1915, showing how light was at the center of the very structure of space and time), time depends locally on gravity and does not “tick” at the same pace everywhere. The reason being that time is influenced by gravitational forces of large masses such as the Earth.
The BGU team asked what would happen to the clock after passing simultaneously through several places where time “ticks” at a different pace once it was in one place again.
They showed that in this very odd situation a new phenomenon presents itself that may, in the future, show that the general theory of relativity plays an important role at the border between the quantum world, in which an object can be in several places simultaneously, and the classical world (as our day-today world of large objects is known), in which an object is not allowed to be in several places at once.
In scientific language, instead of saying that an object (such as a clock) is in several places simultaneously, it is typically said that the object is in a “spatial quantum superposition.” This new terminology is meaningful, the BGU researchers said, because all attempts to interpret the reality of this situation with day-to-day language have led to some sort of contradiction.