A team of physicists from the United States and Russia has developed a new method for calculating a tiny, temperature-dependent source of error in atomic clocks with unprecedented accuracy. The correction could represent a big step towards atomic timekeepers’ longstanding goal of a clock with a precision equivalent to one second of error every 32 billion years.
The research team studied an effect that is familiar to anyone who has basked in the warmth of a campfire: heat radiation. Any object at any temperature, whether the walls of a room, a person, the Sun or a hypothetical perfect radiant heat source known as a “black body,” emits heat radiation. Even a completely isolated atom senses the temperature of its environment. This effect comes into play in the world’s most precise atomic clock, recently built by NIST researchers.
The team used the quantum theory of atomic structure to calculate the blackbody radiation shift of the atomic energy levels of the aluminum ion. Their calculation reduces the relative uncertainty due to room-temperature blackbody radiation in the aluminum ion to 4 x 10-19, or better than 18 decimal places, and a factor of 7 better than previous blackbody radiation calculations. Current aluminum-ion clocks have larger sources of uncertainty than the blackbody radiation effect, but next-generation aluminum clocks are expected to greatly reduce those larger uncertainties and benefit substantially from better knowledge of the blackbody radiation shift.
Keywords: Metrology, Uncertainty, Atomic, Precision, Radiation
