Charles F. A. Baynham
A5068871121- Advanced Frequency and Time Standards
- Atomic and Subatomic Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Fiber Laser Technologies
- Scientific Measurement and Uncertainty Evaluation
- Nonlinear Dynamics and Pattern Formation
- Laser Design and Applications
- Radioactive Decay and Measurement Techniques
- Cardiovascular Syncope and Autonomic Disorders
- Quantum optics and atomic interactions
- Electronic and Structural Properties of Oxides
- Dark Matter and Cosmic Phenomena
- GNSS positioning and interference
- Atmospheric Ozone and Climate
- Hemodynamic Monitoring and Therapy
Imperial College London
2022-2024
National Physical Laboratory
2016-2023
University of Oxford
2016-2020
Abstract Ultrastable lasers are essential tools in optical frequency metrology enabling unprecedented measurement precision that impacts on fields such as atomic timekeeping, tests of fundamental physics, and geodesy. To characterise an ultrastable laser it needs to be compared with a similar performance, but suitable system may not available locally. Here, we report comparison two geographically separated lasers, over the longest ever reported metrological fibre link network, measuring 2220...
We search for transient variations of the fine structure constant using data from a European network fiber-linked optical atomic clocks. By searching coherent in recorded clock frequency comparisons across network, we significantly improve constraints on constant. For example, constrain variation alpha to <5*10^-17 transients duration 10^3 s. This analysis also presents possibility dark matter, mysterious substance hypothesised explain galaxy dynamics and other astrophysical phenomena that...
Abstract We summarise the discussions at a virtual Community Workshop on Cold Atoms in Space concerning status of cold atom technologies, prospective scientific and societal opportunities offered by their deployment space, developments needed before atoms could be operated space. The technologies discussed include atomic clocks, quantum gravimeters accelerometers, interferometers. Prospective applications metrology, geodesy measurement terrestrial mass change due to, e.g., climate change,...
Abstract We present a new framework to study the time variation of fundamental constants in model-independent way. Model independence implies more free parameters than assumed previous studies. Using data from atomic clocks based on 87 Sr, 171 Yb + and 133 Cs, we set bounds controlling fine-structure constant, α , electron-to-proton mass ratio, µ . consider variations timescales ranging minute almost day. In addition, use our results derive some tightest limits date parameter space models...
This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around world to discuss exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter gravitational waves. primary objective was lay groundwork an international TVLBAI proto-collaboration. collaboration aims unite researchers different institutions strategize...
Abstract A full evaluation of the uncertainty budget for ytterbium ion optical clock at National Physical Laboratory (NPL) was performed on electric octupole (E3) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msup> <mml:mrow/> <mml:mn>2</mml:mn> </mml:msup> <mml:msub> <mml:mtext>S</mml:mtext> <mml:mn>1</mml:mn> <mml:mo>/</mml:mo> </mml:mrow> </mml:msub> <mml:mo>→</mml:mo> <mml:mtext>F</mml:mtext> <mml:mn>7</mml:mn> </mml:math> transition. The...
We present a measurement of the absolute frequency 5s$^2$ $^1$S$_0$ to 5s5p $^3$P$_0$ transition in $^{87}$Sr, which is secondary representation SI second. describe optical lattice clock apparatus used for measurement, and we focus detail on how its systematic shifts are evaluated with total fractional uncertainty $1 \times 10^{-17}$. Traceability International System Units provided via comparison Atomic Time (TAI). Gathering data over 5- 15-day periods, operating average 74$\%$ time,...
The highly forbidden $^2$S$_{1/2} \rightarrow ^2$F$_{7/2}$ electric octupole transition in $^{171}$Yb$^+$ is a potential candidate for redefinition of the SI second. We present measurement absolute frequency this optical transition, performed using link to International Atomic Time provide traceability standard was operated 76% 25-day period, with measured be 642 121 496 772 645.14(26) Hz. fractional uncertainty $4.0 \times 10 ^{-16}$ comparable that best previously reported measurement,...
This paper outlines the centralized design and production of ultra-high-vacuum sidearm laser-stabilization systems for AION Ultra-Cold Strontium Laboratories. Commissioning data on residual gas steady-state pressures in chambers, magnetic field quality, laser stabilization, loading rate 3D magneto-optical trap are presented. Streamlining stabilization enabled Collaboration to build equip parallel five state-of-the-art Laboratories within 24 months by leveraging key expertise collaboration....
This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around world to discuss exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter gravitational waves. primary objective was lay groundwork an international TVLBAI proto-collaboration. collaboration aims unite researchers different institutions strategize...
We carried out a 26-day comparison of five simultaneously operated optical clocks and six atomic fountain located at INRIM, LNE-SYRTE, NPL PTB by using two satellite-based frequency techniques: broadband Two-Way Satellite Time Frequency Transfer (TWSTFT) Global Positioning System Precise Point (GPS PPP). With an enhanced statistical analysis procedure taking into account correlations gaps in the measurement data, combined overall uncertainties range $1.8 \times 10^{-16}$ to $3.5 for clock...
Long-baseline atom interferometers, such as the one to be built by AION collaboration, require ultra-cold atomic clouds. These are produced trapping atoms in magneto-optical traps (MOTs) using high-power, narrow-linewidth lasers. We report on laser and optical master–slave injection-locked system used address 1S0–3P1 strontium transition at 689 nm of a narrowband MOT. demonstrate quality injection through characterization lock an easy-to-assemble method that uses double-pass acousto-optic...
A full evaluation of the uncertainty budget for ytterbium ion optical clock at National Physical Laboratory (NPL) was performed on electric octupole (E3) $^2\mathrm{S}_{1/2}\,\rightarrow\, ^2\mathrm{F}_{7/2}$ transition. The total systematic frequency shift measured with a fractional standard $2.2\times 10^{-18}$. Furthermore, absolute E3 transition $^{171}$Yb$^+$ between 2019 and 2023 via link to International Atomic Time (TAI) against local caesium fountain NPL-CsF2. frequencies were...
An atom exposed to an electric field will experience Stark shifts of its internal energy levels, proportional their polarizabilities. In optical frequency metrology, the shift due background black-body radiation (BBR) modifies clock transition, and often represents a large contribution clock's uncertainty budget. For clocks based on singly-ionized ytterbium, ion's complex structure makes this difficult calculate theoretically. We present measurement differential polarizabilities two...
We report a revised absolute frequency measurement of the 171Yb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> electric octupole optical clock transition 642 121 496 772 645.17(22) Hz, with fractional uncertainty 3.4 × 10-16. This newer value, lower uncertainty, is achieved through additional analysis previously reported experimental data that links to SI second international atomic time (TAI). The new step in involves special...
We present a new framework to study the time variation of fundamental constants in model-independent way. Model independence implies more free parameters than assumed previous studies. Using data from atomic clocks based on $^{87}$Sr, $^{171}$Yb$^+$ and $^{133}$Cs, we set bounds controlling fine-structure constant, $α$, electron-to-proton mass ratio, $μ$. consider variations timescales ranging minute almost day. In addition, use our results derive some tightest limits date parameter space...
This paper outlines the centralised design and production of Ultra-High-Vacuum sidearm Laser-Stabilisation systems for AION Ultra-Cold Strontium Laboratories. Commissioning data on residual gas steady-state pressures in chambers, magnetic field quality, laser stabilisation, loading rate 3D Magneto-Optical Trap are presented. Streamlining stabilisation enabled Collaboration to build equip parallel five state-of-the-art Laboratories within 24 months by leveraging key expertise collaboration....
Long-baseline atom interferometers, such as the one to be built by AION collaboration, require ultra-cold atomic clouds. These are produced trapping atoms in Magneto-Optical Traps (MOTs) using high-power, narrow-linewidth lasers. We report on laser and optical master-slave injection locked system used address 1S0 - 3P1 strontium transition at 689 nm, of a narrowband MOT. demonstrate quality through characterisation lock novel, easy-to-assemble method which uses double pass acousto-optic...