Alexandra Tofful

Alexandra is an experimental physicist in the Optical Frequency Metrology group within the Time and Frequency department. She first joined NPL as a PhD student in 2019, working on the ytterbium ion optical clock. After receiving her PhD in early 2023, she continued working on the same project. Alexandra focuses on the continuous improvement of the ytterbium ion optical clock, both in terms of performance and the level of automation of the experiment and data analysis, striving towards high-uptime unattended clock operation. Alexandra has had a leading role in the optimisation and operation of the ytterbium ion optical clock for several clock comparison campaigns, in the measurement and analysis of the systematic frequency shifts, and in the evaluation of the absolute frequency of the optical clock via International Atomic Time. 

Alexandra graduated with a BSc in Physics from King’s College London in 2018, and then proceeded to join the CDT in Controlled Quantum Dynamics at Imperial College London. After receiving an MRes, she moved on to the PhD which was based full time at NPL.  

Areas of interest

• Improving the performance of the ytterbium ion optical clock 
• Clock comparison campaigns for international optical frequency metrology 
• Creating a robust optical clock system with the goal of unattended operation using the ARTIQ framework 
• Writing modular and practical code for data analysis, experimental control and automation 
• Using optical clocks to try and detect oscillations and transient variations in the fine structure constant 

Key publications

• ^​​171Yb⁺ optical clock with 2.2 × 10^-18 systematic uncertainty and absolute frequency measurements 
  A. Tofful, C. F. A. Baynham, E. A. Curtis, A. O. Parsons, B. I. Robertson, M. Schioppo, J. Tunesi, H. S. Margolis, R. J. Hendricks, J. Whale, R. C. Thompson and R. M. Godun  
  Metrologia 61, 045001 (2024) 
• ¹⁷¹Yb⁺ ion optical clock at NPL: advances in automation and assessment of the trap-induced ac Zeeman shift in an endcap trap geometry 
  E. A. Curtis, A. Tofful, A. O. Parsons, B. I. Robertson and R. M. Godun  
  J. Phys.: Conf. Ser. 2889, 012044 (2024) 
• Advances in performance and automation of a single ytterbium ion optical clock 
  A. Tofful, PhD Thesis, Imperial College London (2023) 
• Analysis of atomic-clock data to constrain variations of fundamental constants 
  N. Sherrill, A. O. Parsons, C. F. A. Baynham, W. Bowden, E. A. Curtis, R. Hendricks, I. R. Hill, R. Hobson, H. S. Margolis, B. I. Robertson, M. Schioppo, K. Szymaniec, A. Tofful, J. Tunesi, R. M. Godun, X. Calmet  
  New J. Phys. 25, 093012 (2023) 

E-mail Alexandra Tofful

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