Towards a transportable aluminium ion quantum logic optical clock

Abstract

With the advent of optical clocks featuring fractional frequency uncertainties on the order of 10 −17 and below, new applications such as chronometric levelling with few-cm height resolution emerge. We are developing a transportable optical clock based on a single trapped aluminium ion, which is interrogated via quantum logic spectroscopy. We employ singlycharged calcium as the logic ion for sympathetic cooling, state preparation and readout.Here we present a simple and compact physics and laser package for manipulation of 40 Ca + . Important features are a segmented multi-layer trap with separate loading and probing zones, a compact titanium vacuum chamber, a near-diffraction-limited imaging system with high numerical aperture based on a single biaspheric lens, and an all-in-fiber 40 Ca + repump laser system. We present preliminary estimates of the trap-induced frequency shifts on 27 Al + , derived from measurements with a single calcium ion. The micromotion-induced secondorder Doppler shift for 27 Al + has been determined to be δνEMM ν = −0.4 +0.4 −0.3 × 10 −18 and the black-body radiation shift is δν BBR /ν = (−4.0±0.4)×10 −18 . Moreover, heating rates of 30 (7) quanta per second at trap frequencies of ω rad,Ca+ ≈ 2π × 2.5 MHz (ω ax,Ca+ ≈ 2π × 1.5 MHz) in radial (axial) direction have been measured, enabling interrogation times of a few hundreds of milliseconds.

Optical clock technologies for global navigation satellite systems

“…Ultimate frequency stability at the 10 -18 level is shown by optical lattice and single-ion clocks in rather complex laboratory setups (Ushijima et al 2015;McGrew et al 2018;Delehay and Lacroute 2018). Technology development with respect to transportable setups has been initiated (Koller et al 2017;Cao et al 2017;Brewer et al 2019;Hannig et al 2019), and a compact setup of a 88 Sr lattice clock has been realized, where space-related design criteria have been considered (Bongs et al 2015;Origlia et al 2018). Such optical clocks require several lasers, a vacuum chamber and a cavity pre-stabilization of the clock laser to achieve their outstanding frequency instability enabled by millihertz linewidth transitions.…”

Frequency measurement of the 1 S 0 , F = 5 / 2 ↔ 3 P 1 , F = 7 / 2 transition of 27Al+ via quantum logic spectroscopy with 40Ca+

“…For this reason, there are ongoing efforts in several laboratories for constructing an optical frequency standard based on 27 Al + [16][17][18][19]. In addition, singly charged aluminium ions are a promising candidate for the construction of a transportable optical clock with low fractional systematic uncertainties [20].…”

Point-to-point stabilized optical frequency transfer with active optics

“…Similarly, timescale comparisons between mobile terrestrial optical clocks 1,[52][53][54][55] , where one or more mobile clocks are able to be deployed and moved over an area of interest, enable ground tests of general relativity and local geopotential measurements for research in geophysics, environmental monitoring, surveying, and resource exploration.…”