The ability to juggle atoms may lead to a new breed of atomic clocks with unrivalled accuracy. By launching ultra-cold balls of caesium atoms in rapid succession, it should be possible to measure the frequency of atomic transitions with exceptional precision. Atomic transitions in caesium are currently used to define the fundamental unit of time and form the basis of atomic clocks, but existing caesium clocks use a beam of fast atoms emitted from an oven. While the clocks have an accuracy equivalent to one second in every 3 million years, atomic-clock experts believe that the precision has reached its limit.
This paper explores the potential of quantum entanglement for constructing ultra-precise timekeeping devices, surpassing the limitations of classical clocks. The core concept involves leveraging the inherent correlations within entangled quantum states to achieve unprecedented temporal resolution. We detail a proposed architecture for a quantum entanglement clock, focusing on utilizing the phase-sensitive nature of entangled particles to perform time measurements. The theoretical framework demonstrates how entanglement can fundamentally alter time measurement, offering a pathway towards dramatically improved accuracy. This work highlights the significance of quantum mechanics in redefining the boundaries of precision measurement and opens new avenues for technological advancements in areas such as fundamental physics research, metrology, and navigation systems. This research presents a novel approach to timekeeping, moving beyond the constraints of classical mechanics and into the realm of quantum phenomena.
Rapid progress in the precision and accuracy of optical atomic clocks over the last decade has advanced the frontiers of timekeeping, metrology, and quantum science. However, the stabilities of most optical clocks remain limited by the local oscillator rather than the atoms themselves, leaving room for further progress. Here we implement a "multiplexed" one-dimensional optical lattice clock, in which spatially-resolved, movable ensembles of ultra-cold strontium atoms are trapped in the same optical lattice, interrogated simultaneously by a shared clock laser, and read-out in parallel. By performing synchronized Ramsey interrogations of ensemble pairs we observe atom-atom coherence times up to 26 seconds, a 270-fold improvement over the atom-laser coherence time, demonstrate a relative stability of 9.7(4)×10−18/τ (where τ is the averaging time in seconds), and reach a fractional uncertainty of 8.9(3)×10−20 after 3.3 hours of averaging. These results demonstrate that applications requiring ultra-high-precision comparisons between optical atomic clocks need not be limited by the stability of the local oscillator. With multiple ensemble pairs, we realize a miniaturized clock network consisting of 6 atom ensembles, resulting in 15 unique pairwise clock comparisons with relative stabilities below 3×10−17/τ. Finally, we demonstrate the capability to simultaneously load spatially-resolved, heterogeneous ensemble pairs of all four stable isotopes of strontium in a lattice. The unique capabilities offered by this platform pave the way for future studies of precision isotope shift measurements, spatially resolved characterization of limiting clock systematics, development of clock-based gravitational wave and dark matter detectors, and novel tests of relativity including measurements of the gravitational redshift at sub-centimeter scales.