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Experts have built a new type of atomic clock that could preserve exact time to a tenth of a second, if left to run for 14 billion years, roughly the current age of the universe.
The American experts’ design takes advantage of a strange phenomenon called quantum entanglement, in which the particles are closely related.
The researchers explained that this entanglement helps reduce the uncertainty involved in measuring the oscillations of atoms that atomic clocks use to keep time.
The clock can be used to help discover “dark matter”, which is believed to make up more than three-quarters of the universe, and study the effect of gravity over time.
“The entanglement-enhanced optical atomic clocks will have the ability to achieve better resolution in one second than the latest current optical clocks,” said the paper’s author and electrical engineer Edwin Pedroso Penafiel of the Massachusetts Institute of Technology.
Atomic clocks use lasers to measure the regular oscillations of clouds of atoms, the most stable periodic events that scientists can now observe.
Ideally, the motion of an atom could be used. However, on atomic scales, the strange rules of quantum mechanics play an important role, and measurements are subject to probabilities that must be averaged to obtain reliable data.
“When the number of atoms increases, the average given by all these atoms is directed towards something that gives the correct value”, explains the author and physicist of the paper, Simon Colombo, of the Massachusetts Institute of Technology.
Today’s atomic clocks take measurements of thousands of supercooled atoms, which are trapped in an optical “trap” using a laser and examined by a laser of a different frequency similar to the vibrations of the atoms being measured.
However, even this approach is subject to a degree of quantum uncertainty, but, as the team has shown, some of it can be eliminated by switching to quantum entanglement, where clusters of atoms give coherent measurements.
The researchers explained that this means that the individual oscillations of the entangled atoms contract around a common frequency, increasing the precision of the measurements taken by the watch.
In their new design, Dr. Pedrozo Penafiel and his colleagues entwined about 350 atoms of the rare earth element ytterbium, which oscillates 100,000 times per second more than cesium, the element used in conventional atomic clocks.
This fact means that, if carefully monitored, the new watch can distinguish even the smallest interior parts of the time.
As with a normal atomic clock, the team trapped the atoms in a cavity of light surrounded by two mirrors, then fired a laser through the cavity to bounce between the mirrors, repeatedly interacting with the atoms and their entanglement.
“It is as if the light acts as a link between the atoms,” said physicist Chi Shuo of the Massachusetts Institute of Technology. The first atom that sees this light will modify the light a bit, and this light will also modify the second atom and the third atom, and through many rounds, the atoms collectively know each other and begin to behave similarly.
The team then used another laser to measure the average frequency of the atoms, similar to the method used in today’s atomic clocks. The team found that entanglement allowed the watch to achieve the required precision four times faster.
“You can always make the clock more accurate by measuring for longer,” said MIT physicist Vladan Volletek.
Professor Voltek added that the new watch design could be used to better address the various secrets of the universe, according to the “Daily Mail.”
