Atomic Combination Clocks

TL;DR

This paper proposes a novel atomic clock design using entangled superpositions of multiple atomic species to reduce susceptibility to external disturbances, enhancing stability and accuracy.

Contribution

It introduces a new method of atomic clock construction employing entangled multi-species superpositions to improve stability and systematic shift reduction.

Findings

Superpositions of different atomic species can destructively interfere susceptibilities.

Two specific examples demonstrate reduced external field sensitivities.

The approach improves clock stability and reduces systematic errors.

Abstract

Atomic clocks use atomic transitions as frequency references. The susceptibility of the atomic transition to external fields limits clock stability and introduces systematic frequency shifts. Here, we propose to realize an atomic clock that utilizes an entangled superposition of states of multiple atomic species, where the reference frequency is a sum of the individual transition frequencies. The superposition is selected such that the susceptibilities of the respective transitions, in individual species, destructively interfere leading to improved stability and reduced systematic shifts. We present and analyze two examples of such combinations. The first uses the optical quadrupole transitions in a $^{40}$Ca$^+$ - $^{174}$Yb$^+$ two-ion crystal. The second is a superposition of optical quadrupole transitions in one $^{88}$Sr$^+$ ion and three $^{202}$Hg$^+$ ions. These combinations have reduced susceptibility to external magnetic fields and blackbody radiation.