Algorithmic Ground-State Cooling of Weakly Coupled Oscillators Using Quantum Logic

New Horizons: Scalar and Vector Ultralight Dark Matter

“…Several proposals based on HCI optical clocks, their fundamental physics applications, and experimental progress towards HCI high-precision spectroscopy were reviewed in [320]. Recent development of HCI cooling, trapping, and quantum logic techniques are enabling rapid progress in the development of HCI clocks [321,344]. HCI clocks enable clock-comparisons with ∆K ≈ 100 [325].…”

“…Slowing and trapping of HCIs in Paul traps using laser-cooled beryllium [374] was the first step towards the first coherent laser spectroscopy using quantum logic [321]. Algorithmic ground state cooling enabled full control over the motional state and a suppression of Doppler shifts below the 10 −18 level [344]. Recently, the first optical clock based on a HCI has been demonstrated with atom-related systematic uncertainties at a level of 10 −18 and below [375].…”

An ultralow-noise superconducting radio-frequency ion trap for frequency metrology with highly charged ions

“…A few years ago, sympathetic cooling of HCI transferred from an EBIT into a cryogenic Paul trap containing a laser-cooled Coulomb crystal of 9 Be + ions brought down the accessible temperatures of trapped HCI from the megakelvin into the millikelvin range. 35 Later, a pioneering experiment in a Penning trap performed spectroscopy on the forbidden optical fine-structure transition in 40 Ar 13+ at 441 nm at higher ion temperatures (T ≈ 1K) by laser-induced excitation and subsequent detection through a measurement of the electronic ground-state spin orientation, 36 reaching a relative uncertainty of ∆ν/ν 9.4 × 10 −9 . The potential of HCI for optical frequency metrology was finally unleashed with the recent ground-state cooling of the axial modes of motion (T < 50 µK) of a two-ion crystal consisting of one HCI and one 9 Be + ion and the subsequent application of QLS in a Paul trap to the aforementioned forbidden transition in 40 Ar 13+ , reporting a statistical uncertainty of ∆ν/ν 10 −15 .…”

“…35 Later, a pioneering experiment in a Penning trap performed spectroscopy on the forbidden optical fine-structure transition in 40 Ar 13+ at 441 nm at higher ion temperatures (T ≈ 1K) by laser-induced excitation and subsequent detection through a measurement of the electronic ground-state spin orientation, 36 reaching a relative uncertainty of ∆ν/ν 9.4 × 10 −9 . The potential of HCI for optical frequency metrology was finally unleashed with the recent ground-state cooling of the axial modes of motion (T < 50 µK) of a two-ion crystal consisting of one HCI and one 9 Be + ion and the subsequent application of QLS in a Paul trap to the aforementioned forbidden transition in 40 Ar 13+ , reporting a statistical uncertainty of ∆ν/ν 10 −15 . 37 One major effect that systematically limits the achievable accuracy in Paul trap experiments is the timedilation shift caused by residual ion motion, which represents a key problem for frequency standards based on singly charged ions.…”

“…The resonant quadrupole mode (QM) of its electric field generates an ultrastable pseudopotential that radially confines the ions. Originally developed for experiments with HCI, which are expected to exhibit higher heating rates than singly charged ions, 39,40 the technique can also be applied to any other ion species.…”