Abstract
We present a novel method for engineering an optical clock transition that is robust against external field fluctuations and is able to overcome limits resulting from field inhomogeneities. The technique is based on the application of continuous driving fields to form a pair of dressed states essentially free of all relevant shifts. Specifically, the clock transition is robust to magnetic field shifts, quadrupole and other tensor shifts, and amplitude fluctuations of the driving fields. The scheme is applicable to either a single ion or an ensemble of ions, and is relevant for several types of ions, such as , , and . Taking a spherically symmetric Coulomb crystal formed by 400 ions as an example, we show through numerical simulations that the inhomogeneous linewidth of tens of Hertz in such a crystal together with linear Zeeman shifts of order 10 MHz are reduced to form a linewidth of around 1 Hz. We estimate a two-order-of-magnitude reduction in averaging time compared to state-of-the art single ion frequency references, assuming a probe laser fractional instability of . Furthermore, a statistical uncertainty reaching 2.9 × 10−16 in 1 s is estimated for a cascaded clock scheme in which the dynamically decoupled Coulomb crystal clock stabilizes the interrogation laser for an clock.
Highlights
Optical clocks based on neutral atoms trapped in optical lattices and single trapped ions have reached estimated systematic uncertainties of a few parts in 10−18 [1,2,3,4] or even below [5]
In contrast to neutral atom lattice clocks, which are typically probed with hundreds to thousands of atoms, single ion clocks are currently limited in their statistical uncertainty by quantum projection noise [21] to levels of a few parts in 10-15 t [3, 22, 23]
We have proposed a continuous dynamical decoupling (CDD) scheme that significantly suppresses the Zeeman shift as well as the quadrupole and tensor ac Stark frequency shifts of an optical clock transition for ion crystals
Summary
We present a novel method for engineering an optical clock transition that is robust against external field author(s) and the title of the work, journal citation fluctuations and is able to overcome limits resulting from field inhomogeneities. The application of continuous driving fields to form a pair of dressed states essentially free of all relevant shifts. Taking a spherically symmetric Coulomb crystal formed by 400 40Ca+ ions as an example, we show through numerical simulations that the inhomogeneous linewidth of tens of Hertz in such a crystal together with linear Zeeman shifts of order 10 MHz are reduced to form a linewidth of around 1 Hz. We estimate a twoorder-of-magnitude reduction in averaging time compared to state-of-the art single ion frequency references, assuming a probe laser fractional instability of 10-15. A statistical uncertainty reaching 2.9 × 10−16 in 1 s is estimated for a cascaded clock scheme in which the dynamically decoupled Coulomb crystal clock stabilizes the interrogation laser for an 27Al+ clock
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