A quantum clock is a type of atomic clock with laser cooled single ions confined together in an electromagnetic ion trap. Developed by National Institute of Standards and Technology physicists, the clock is 37 times more precise than the existing international standard. The quantum logic clock is based on an aluminium spectroscopy ion with a logic atom.
Both the aluminium-based quantum clock and the mercury-based optical atomic clock track time by the ion vibration at an optical frequency using a UV laser, that is 100,000 times higher than the microwave frequencies used in NIST-F1 and other similar time standards around the world. Quantum clocks like this are able to be far more precise than microwave standards and current optical clocks.
In terms of standard deviation, the quantum logic clock loses one second every 3.4 billion years, while the current international standard NIST-F1 caesium fountain atomic clock loses a second every 100 million years.
The NIST team are not able to measure clock ticks per second because the definition of a second is based on the NIST-F1 which cannot measure a more precise machine. However the aluminium ion clock's measured frequency to the current standard is 1121015393207857.4(7)Hz. NIST have attributed the clock's accuracy to the fact that it is insensitive to background magnetic and electric fields, and unaffected by temperature.
In February 2010, NIST physicists built a second, enhanced, version of the single aluminium atom quantum logic clock using a Be+logic ion instead of the a Mg ion . Considered the world's most precise clock, it offers more than twice the precision of the original, losing one second in 3.7 billion years.
The accuracy of quantum clocks has since been superseded by optical lattice clocks based on strontium-87 and ytterbium-171. Clocks based on the latter exhibit stability greater than a tenth of a second over the age of the universe.
Gravitational time dilation
In 2010 an experiment placed two aluminium-ion quantum clocks close to each other, but with the second elevated 12 in (30.5 cm) compared to the first, making the gravitational time dilation effect visible in everyday lab scales.
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