When it comes to atomic clocks, every second counts. In fact,
according to Marianna Safronova, every quintillionth of a second counts.
The UD associate professor of physics and colleagues from the Petersburg Nuclear Physics Institute in Russia and the Joint Quantum Institute in Maryland have devised a new calculation to aid ultra-precise timekeeping. Their findings could lead to the development of an atomic clock that loses only a second in about 32 billion years — that's more than twice the age of the universe.
"Extremely high-precision clocks have a lot of applications, from tracking deep-space probes to testing the fundamental principles of science," says Safronova, noting that all global positioning systems (GPS) are based on atomic clocks.
The world's most precise clock, developed last year by the National Institute for Standards and Technology in Boulder, Colo., loses about a second every 3.7 billion years. It is a quantum-logic clock, which is based on the atomic energy levels in the aluminum-plus ion, an aluminum atom that has lost one electron. The electrons in the ion vibrate between their highest energy orbit, or excited state, and lowest energy orbit, or ground state, at an extremely precise frequency, and that frequency is what the atomic clock uses to keep time.
"You have to know that difference to evaluate the accuracy of the clock, but it turns out that the frequency does change very slightly with temperature," Safronova says. "The frequency is defined at absolute zero, but the room isn't at absolute zero."
The temperature affects the ion's transition frequency because heat — even the tiny amount that exists throughout the environment and is known as "blackbody radiation" — changes the size of the electron clouds and causes the two energy levels to shift. She and her team have calculated a way to account for that very small shift.