The Al ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of Al ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al traps are utilized. The first trap is used to trap a large number of Al ions to improve the stability of the clock laser, while the second trap is used to trap a single Al ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167 nm laser. The expected clock laser stability can reach . For the second trap, in addition to 167 nm laser Doppler cooling, a second stage pulsed 234 nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about . The proposed Al ion optical clock has the potential to become the most accurate and stable optical clock .The Al ion optical clock is a very promising optical frequency standard candidate due to its extremely small black-body radiation shift. It has been successfully demonstrated with the indirect cooled, quantum-logic-based spectroscopy technique. Its accuracy is limited by second-order Doppler shift, and its stability is limited by the number of ions that can be probed in quantum logic processing. We propose a direct laser cooling scheme of Al ion optical clocks where both the stability and accuracy of the clocks are greatly improved. In the proposed scheme, two Al traps are utilized. The first trap is used to trap a large number of Al ions to improve the stability of the clock laser, while the second trap is used to trap a single Al ion to provide the ultimate accuracy. Both traps are cooled with a continuous wave 167 nm laser. The expected clock laser stability can reach . For the second trap, in addition to 167 nm laser Doppler cooling, a second stage pulsed 234 nm two-photon cooling laser is utilized to further improve the accuracy of the clock laser. The total systematic uncertainty can be reduced to about . The proposed Al ion optical clock has the potential to become the most accurate and stable optical clock .

arXiv:1609.03667Chinese Physics LettersMay 1, 201714 citations

Al+ Optical Clocks for Fundamental Physics and Geodesy

James Chin-wen Chou

Laser-cooled trapped atoms have long been recognized as potentially very accurate frequency standards for clocks. Ultimate accuracies of 10-18 to 10-19 appear possible, limited by the time-dilation of trapped ions that move at laser-cooled velocities. The Al+ ion is an attractive candidate for high accuracy, owing to its narrow electronic transition in the optical regime and low sensitivity to ambient field perturbations. Precision spectroscopy on Al+ is enabled by quantum information techniques. With Al+ “quantum-logic” clocks, the current accuracy of 8.6×10-18 has enabled a geo-potential-difference measurement that detected a height change of 37±17 cm due to the gravitational red-shift. We have also observed quantum coherence between two Al+ ions with a record Q-factor of 3.4×1016, and compared the Al+ resonance frequency to that of a single Hg+ ion to place limits on the temporal variation of the fine-structure constant.Laser-cooled trapped atoms have long been recognized as potentially very accurate frequency standards for clocks. Ultimate accuracies of 10-18 to 10-19 appear possible, limited by the time-dilation of trapped ions that move at laser-cooled velocities. The Al+ ion is an attractive candidate for high accuracy, owing to its narrow electronic transition in the optical regime and low sensitivity to ambient field perturbations. Precision spectroscopy on Al+ is enabled by quantum information techniques. With Al+ “quantum-logic” clocks, the current accuracy of 8.6×10-18 has enabled a geo-potential-difference measurement that detected a height change of 37±17 cm due to the gravitational red-shift. We have also observed quantum coherence between two Al+ ions with a record Q-factor of 3.4×1016, and compared the Al+ resonance frequency to that of a single Hg+ ion to place limits on the temporal variation of the fine-structure constant.

Jul 13, 20110 citations

Universal Linear Optics: A Testbed for Optical Quantum Logic

Chris Sparrow, Jacques Carolan, Christopher Harrold +13 more

Bulletin of the American Physical SocietyMar 17, 20160 citations

Direct Laser Cooling Al

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Ion Optical Clocks