Abstract:

In essence, the accuracy and performance of an atomic clock ultimately depends on various systematic shifts in the narrow-linewidth transition in an isolated atomic system. Lutetium ion possesses multiple advantageous properties that make it a promising candidate to serve as an optical frequency standard. First of all, it has multiple narrow-linewidth transitions from the 1S0 electronic ground state to the low-lying meta-stable D states that are potentially good optical clock transition [1]. Secondly, the 3D1↔3P0 cooling transition has a relatively small linewidth of 2π×2.6 MHz which potentially allows lower temperature at the Doppler limit when compared to other ion species. Furthermore, 176Lu+ has a large nuclear spin of I = 7, which enable a hyperfine averaging technique to be employed for the realization of an effective J = 0 level that eliminate the electric quadrupole shift [2]. In this talk, I will give summary of the recent experimental progress of 176Lu+-based optical clock carried out at the Centre for Quantum Technologies at National University of Singapore. Laser spectroscopy has been performed for all transitions relevant for the manipulations of the ion's internal state for clock operation; accuracy as low as a few kHz had been achieved [3]. We also characterize the blackbody radiation (BBR) shifts for the 1S0 ↔ 3D1 and 1S0 ↔ 3D2 transitions by directly measuring the static differential scalar polarizability using a CO2 laser at 10.6 _m [4]. At 300 K, the fractional BBR shift of the 1S0 ↔ 3D1 transition is -1.36(9)×10^-18; this is the lowest among all optical clock candidates currently under investigations. For the 1S0 ↔ 3D2 transition, the scalar polarizability is found to be of negative value. This allows the exact cancellation of the two important shifts (i.e. second-order Doppler shift and AC Stark shift) due to micromotion when operate at a RF trapping frequency of RF = 2π×32.9(1.3) MHz [5]. Operating at such a “magic RF” opens the possibility of a multi-ion optical clock where the clock's stability can be enhanced without the expense of accuracy due to complications associate with micromotion [6].

 

[1] E. Paez, K. J. Arnold, E. Hajiyev, S. G. Porsev, V. A. Dzuba, U. I. Safronova, M. S. Safronova, and M. D. Barrett, “Atomic properties of Lu+,” Phys. Rev. A 93, 042112 (2016).

[2] M. D. Barrett, “Developing a field independent frequency reference,” New J. Phys. 17, 053024 (2015).

[3] R. Kaewuam, A. Roy, T. R. Tan, K. J. Arnold, and M. D. Barrett. “Laser spectroscopy of 176Lu+,” J. Mod. Opt. 65, 592 (2017).

[4] K. J. Arnold, R. Kaewuam, A. Roy, T. R. Tan, and M. D. Barrett. “Blackbody radiation shift assessment for a lutetium ion clock,” Nat. Commun. 9, 1650 (2018).

[5] D. J. Berkland, J. D. Miller, J. C. Bergquist, W. M. Itano, and D. J. Wineland, “Minimization of ion micromotion in a Paul trap,” J. Appl. Phys. 83, 5025 (1998).

[6] K. Arnold, E. Hajiyev, E. Paez, C. H. Lee, M. D. Barrett, and J. Bollinger, “Prospects for atomic clocks based on large ion crystals,” Phys. Rev. A 92, 032108 (2015).

 

 

Short Bio:

Tan Ting Rei did his graduate research works at National Institute of Standards and Technology (NIST) under the supervision of Dr. David J. Wineland, a physics Nobel Laureate in 2012. Working with trapped ions, Ting Rei focused on experimental quantum information processing and the foundation of quantum mechanics; research highlights include the first Chained Bell inequality test with massive particles and the creation of quantum entanglement with two different species of ion. The latter was selected by the Institute of Physics (IOP) as one of the top ten physics breakthrough of 2016. After graduated from the University of Colorado – Boulder, he joined Assoc. Prof. Murray Barrett’s group at the Centre for Quantum Technologies working on developing the world first's atomic clock based on lutetium (Lu) ions. Ting Rei is currently a Lee Kuan Yew postdoctoral fellow.