Scientists have described a prototype atomic-array optical tweezer clock that combines the advantages of single-atom and optical-lattice clocks. The most precise and reliable optical clocks currently rely on the optical probing of either a single ion or a group of neutral atoms in an optical lattice.
An array of about 40 strontium atoms, each one caught by an optical tweezer, forms the foundation of the prototype optical tweezer clock. The researchers first load the array with cold atomic cloud material to remove greater trap occupancies.
The team then excites each particle with a laser, measuring its fluorescence with a camera. The researchers conduct two separate interrogations, one below resonance and one above, to produce an erroneous signal. They claim that this atom-by-atom feedback control allows accurate estimation of the contribution of laser noise.
The laser light’s oscillations create a pendulum that measures the passing of time. The atoms serve as an extremely trustworthy reference to ensure that the pendulum swings at a consistent speed.
Compared to the single-atom case, the 40 strontium atoms used by the Caltech researchers represent a sufficient quantity to reduce quantum noise significantly. “Disruptive atomic interactions” are reduced thanks to the atoms’ multiple-micron spacing.
According to the study’s authors, an advanced cavity-stabilized clock laser allowed for coherence-preserving atomic interrogations of up to four seconds—an impressive number for a tweezer clock and any optical clock.
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