Coherent laser spectroscopy of highly charged ions using quantum logic

Micke, P.; Leopold, Tobias; King, Simon; Benkler, E.; Spieß, Lukas J.; Schmöger, Lisa; Schwarz, Maria A.; López‐Urrutia, J. R. Crespo; Schmidt, Piet O.

doi:10.1038/s41586-020-1959-8

Cited by 126 publications

(99 citation statements)

References 56 publications

(135 reference statements)

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“…Such reduced coupling is expected to improve the achievable accuracy of time measurement [261]. Alternative approaches being investigated are atomic clocks based on highly charged ions [196,223,313], superradiant optical clocks [31,245], neutral atoms in tweezer arrays [212,246] and multiple ion clocks [133,183,184,276]. A detailed discussion of the nuclear clock concept will be given in the following.…”

Section: A Nuclear Optical Clock For Time Measurementmentioning

confidence: 99%

The $$^{229}$$Th isomer: prospects for a nuclear optical clock

Wense

2020

Eur. Phys. J. A

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The proposal for the development of a nuclear optical clock has triggered a multitude of experimental and theoretical studies. In particular the prediction of an unprecedented systematic frequency uncertainty of about $$10^{-19}$$ 10 - 19 has rendered a nuclear clock an interesting tool for many applications, potentially even for a re-definition of the second. The focus of the corresponding research is a nuclear transition of the $$^{229}$$ 229 Th nucleus, which possesses a uniquely low nuclear excitation energy of only $$8.12\pm 0.11$$ 8.12 ± 0.11 eV ($$152.7\pm 2.1$$ 152.7 ± 2.1 nm). This energy is sufficiently low to allow for nuclear laser spectroscopy, an inherent requirement for a nuclear clock. Recently, some significant progress toward the development of a nuclear frequency standard has been made and by today there is no doubt that a nuclear clock will become reality, most likely not even in the too far future. Here we present a comprehensive review of the current status of nuclear clock development with the objective of providing a rather complete list of literature related to the topic, which could serve as a reference for future investigations.

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Section: A Nuclear Optical Clock For Time Measurementmentioning

confidence: 99%

The $$^{229}$$Th isomer: prospects for a nuclear optical clock

Wense

2020

Eur. Phys. J. A

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“…Highly-charged-ion-based optical clocks with negligible sensitivity to BBR have also been studied [22][23][24]. However, for many of the systems described above, they often require using deepultraviolet light sources; for some of the clocks, they can only be achieved with quantum logic spectroscopy [12].…”

mentioning

confidence: 99%

A liquid nitrogen-cooled Ca+ optical clock with systematic uncertainty of 3×10-18

Huang¹,

Zhang²,

Zeng³

et al. 2021

Preprint

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Here we present a liquid nitrogen-cooled Ca+ optical clock with an overall systematic uncertainty of 3×10-18. In contrast with the room-temperature Ca+ optical clock that we have reported previously, the temperature of the blackbody radiation (BBR) shield in vacuum has been reduced to 82(5) K using liquid nitrogen. An ion trap with a lower heating rate and improved cooling lasers were also introduced. This allows cooling the ion temperature to the Doppler cooling limit during the clock operation, and the systematic uncertainty due to the ion’s secular (thermal) motion is reduced to < 1×10-18. The uncertainty due to the probe laser light shift and the servo error are also reduced to < 1×10-19 and 4×10-19 with the hyper-Ramsey method and the higher-order servo algorithm, respectively. By comparing the output frequency of the cryogenic clock to that of a room-temperature clock, the differential BBR shift between the two was measured with a fractional statistical uncertainty of 7×10-18. The differential BBR shift was used to calculate the static differential polarizability, and it was found in excellent agreement with our previous measurement with a different method. This work suggests that the BBR shift of optical clocks can be well suppressed in a liquid nitrogen environment. This is advantageous because conventional liquid-helium cryogenic systems for optical clocks are more expensive and complicated. Moreover, the proposed system can be used to suppress the BBR shift significantly in other types of optical clocks such as Yb+, Sr+, Yb, Sr, etc.

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“…Another technique was proposed over thirty years ago to extend laser cooling to antimatter and other exotic systems by coupling to ions with a well-suited cooling transition via ion-induced image currents in trap electrodes [9]. In other contexts, * matthew.bohman@mpi-hd.mpg.de coupling of laser addressable ions to systems with no optical structure has also long been desired for precision spectroscopy [24,25], mass measurements [26], quantum information [10], and the realisation of novel quantum systems [5].…”

mentioning

confidence: 99%

“…In measurements of nuclear magnetic moments this will enable nearly 100% spin-flip fidelity [11,16,17,38] and can reduce the dominant systematic effect proportional to the particle temperature in the highest precision mass measurements [39][40][41]. In addition, this technique can also be used to cool other exotic systems such as highly charged ions [24,25] or molecular ions [18,42] for sideband resolved spectroscopy, using only a single cooling laser. The sympathetically cooled resonator can also be used as a sensitivity enhanced probe of new physics, for example in dark matter searches [13,42,43].…”

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confidence: 99%

LC circuit mediated sympathetic cooling of a proton via image currents

Bohman

Grunhofer²,

Smorra

et al. 2021

Preprint

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Efficient cooling of trapped charged particles is essential in many fundamental physics experiments, for high-precision metrology, and for quantum technology. Until now, ion-ion coupling for sympathetic cooling or quantum state control has been limited to ion species with accessible optical transitions or has required close-range Coulomb interactions. To overcome this limitation and further develop scalable quantum control techniques, there has been a sustained desire to extend laser-cooling techniques to particles in macroscopically separated traps, opening quantum control techniques to previously inaccessible particles such as highly charged ions, molecular ions, and antimatter particles. Here, we demonstrate sympathetic cooling of a single proton by laser cooled Be+ ions stored in a spatially separated Penning trap. The two traps are connected by a superconducting LC circuit that enables energy exchange over a distance of 9 cm. We simultaneously demonstrate the cooling of a resonant mode of a macroscopic LC circuit with laser-cooled ions and sympathetic cooling of an individually trapped proton, reaching temperatures far below the environment temperature. Importantly, as this technique does not rely on the direct Coulomb interaction but rather on image-current interactions, it can be easily applied to an experiment with antiprotons, facilitating improved precision in matter-antimatter comparisons and dark matter searches.

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Coherent laser spectroscopy of highly charged ions using quantum logic

Cited by 126 publications

References 56 publications

The $$^{229}$$Th isomer: prospects for a nuclear optical clock

The $$^{229}$$Th isomer: prospects for a nuclear optical clock

A liquid nitrogen-cooled Ca+ optical clock with systematic uncertainty of 3×10-18

LC circuit mediated sympathetic cooling of a proton via image currents

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