A5020015806- Advanced Frequency and Time Standards
- Atomic and Subatomic Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Advanced Fiber Laser Technologies
- Semiconductor Lasers and Optical Devices
- Dark Matter and Cosmic Phenomena
- Scientific Measurement and Uncertainty Evaluation
- Computational Physics and Python Applications
- Satellite Communication Systems
- Advanced Computational Techniques and Applications
- Quantum optics and atomic interactions
- Nonlinear Dynamics and Pattern Formation
- Advanced Measurement and Metrology Techniques
- Multilevel Inverters and Converters
- Laser-Ablation Synthesis of Nanoparticles
- Laser Material Processing Techniques
- Photonic and Optical Devices
- Semiconductor Quantum Structures and Devices
- Cardiovascular Syncope and Autonomic Disorders
- Manufacturing Process and Optimization
- Advanced Electrical Measurement Techniques
- 3D Printing in Biomedical Research
- Sensorless Control of Electric Motors
- Laser-induced spectroscopy and plasma
- Advanced Numerical Analysis Techniques
National Physical Laboratory
2016-2023
University of Oxford
2016-2020
Imperial College London
2020
University of British Columbia
2011-2016
Canada's Michael Smith Genome Sciences Centre
2011
BC Cancer Agency
2011
We outline the experimental concept and key scientific capabilities of AION (Atom Interferometer Observatory Network), a proposed programme using cold strontium atoms to search for ultra-light dark matter, explore gravitational waves in mid-frequency range between peak sensitivities LISA LIGO/Virgo/ KAGRA/INDIGO/Einstein Telescope/Cosmic Explorer experiments, probe other frontiers fundamental physics. would complement planned searches as well mergers involving intermediate-mass black holes...
Abstract We propose in this White Paper a concept for space experiment using cold atoms to search ultra-light dark matter, and detect gravitational waves the frequency range between most sensitive ranges of LISA terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment Dark Matter Gravity Exploration (AEDGE), will also complement other planned searches exploit synergies with wave detectors. give examples extended sensitivity matter offered...
Phase compensated optical fiber links enable high accuracy atomic clocks separated by thousands of kilometers to be compared with unprecedented statistical resolution. By searching for a daily variation the frequency difference between four strontium lattice in different locations throughout Europe connected such links, we improve upon previous tests time dilation predicted special relativity. We obtain constraint on Robertson--Mansouri--Sexl parameter $|\alpha|\lesssim 1.1 \times10^{-8}$...
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 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...
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...
Abstract We realize a two-stage, hexagonal pyramid magneto-optical trap (MOT) with strontium, and demonstrate loading of cold atoms into cavity-enhanced 1D 2D optical lattice traps, all within single compact assembly in-vacuum optics. show that the device is suitable for high-performance quantum technologies, focusing especially on its intended application as strontium clock. prepare 2 × 10 4 spin-polarized 87 Sr in 500 ms; we observe vacuum-limited lifetime 27 s; measure background DC...
We develop a method of modified hyper-Ramsey spectroscopy in optical clocks, achieving complete immunity to the frequency shifts induced by probing fields themselves. Using particular pulse sequences with tailored phases, frequencies, and durations, we can derive an error signal centered exactly at unperturbed atomic resonance steep discriminant which is robust against variations probe shift. experimentally investigate scheme using magnetically-induced $^1$S$_0- ^3$P$_0$ transition...
We describe the Sr optical lattice clock apparatus at NPL with particular emphasis on techniques used to increase reliability and minimise human requirement in its operation. Central this is a clock-referenced transfer cavity scheme for stabilisation of cooling trapping lasers. highlight several measures view towards realisation an time-scale. The contributed 502 hours data over 25 day period (84% uptime) recent measurement campaign uninterrupted periods more than 48 hours. An instability...
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,...
Quantum nondemolition (QND) measurement is a remarkable tool for the manipulation of quantum systems. It allows specific information to be extracted while still preserving fragile observables system. Here we apply cavity-based QND an optical lattice clock—a type atomic clock with unrivaled frequency precision—preserving coherence atoms after readout 80% fidelity. We this technique stabilize phase ultrastable laser coherent state via series repeated measurements. exploit improved interrogate...
Electrometry is performed using Rydberg states to evaluate the quadratic Stark shift of $5{s}^{2}\phantom{\rule{0.16em}{0ex}}^{1}S_{0}\ensuremath{-}5s5p\phantom{\rule{0.16em}{0ex}}^{3}P_{0}$ clock transition in strontium. By measuring highly excited $5s75d\phantom{\rule{0.16em}{0ex}}^{1}D_{2}$ state electromagnetically induced transparency, we characterize electric field with sufficient precision provide tight constraints on systematic transition. Using theoretically derived, and...
We create atom-molecule dark states in a degenerate Fermi gas of $^{6}\mathrm{Li}$ both weakly and strongly interacting regimes using two-photon Raman scattering to couple fermion pairs bound molecular the ground singlet triplet potential. Near unitarity point BEC-BCS crossover regime, atom number revival height associated with state abruptly unexpectedly decreases remains low for magnetic fields below Feshbach resonance center at 832.2 G. With 0 G, we perform precision dark-state...
We demonstrate a new method of cavity-enhanced non-destructive detection atoms for strontium optical lattice clock. The scheme is shown to be linear in atom number up at least 2×104 atoms, reject technical noise sources, achieve signal ratio close the photon shot limit, provide spatially uniform atom-cavity coupling, and minimize inhomogeneous ac Stark shifts. These features enable with minimal perturbation atomic state, critical step towards realizing an ultra-high-stability, quantum-enhanced
We report on the realization of a magneto-optical trap (MOT) for metastable strontium operating 2.92-$\ensuremath{\mu}\mathrm{m}$ transition between energy levels $5s5p{\phantom{\rule{0.16em}{0ex}}}^{3}{P}_{2}$ and $5s4d{\phantom{\rule{0.16em}{0ex}}}^{3}{D}_{3}$. The atoms are initially captured in MOT 461-nm $5{s}^{2}{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ $5s5p{\phantom{\rule{0.16em}{0ex}}}^{1}{P}_{1}$, prior to being transferred into cooled final temperature 6...
We report the design and characterization of an optical shutter based on a piezoelectric cantilever. Compared to conventional electro-magnetic shutters, device is intrinsically low power acoustically quiet. The cantilever position controlled by high-voltage op-amp circuit for easy tuning range travel, mechanical slew rate, which enables factor 30 reduction in noise compared rapidly switched device. achieve shuttering rise fall times 11 $\mu$s, corresponding rates 1.3 $\textrm{ ms}^{-1}$,...
We present a dual-species effusive source and Zeeman slower designed to produce slow atomic beams of two elements with large mass difference very different oven temperature requirements. demonstrate this design for the case 6Li 85Rb achieve magneto-optical trap (MOT) loading rates equivalent that reported in prior work on dual species (Rb+Li) slowers operating at same temperatures. Key choices, including thermally separating sources using segmented coil enable computer control magnetic field...
We present a field-programmable gate array (FPGA) based control system that has been implemented to strontium optical lattice clock at the National Physical Laboratory, UK. Bespoke printed circuit boards have designed and manufactured, including an 8-channel, 16-bit digital analog converter board with 2 μs update rate 4-channel direct-digital synthesis clocked 1 GHz. Each includes its own FPGA 28 output lines available alongside specialized or radio frequency outputs. The is scalable large...
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...
There has been tremendous progress in the performance of optical frequency standards since first proposals to carry out precision spectroscopy on trapped, single ions 1970s. The estimated fractional uncertainty today's leading is currently $10^{-18}$ range, approximately two orders magnitude better than that best caesium primary standards. This exceptional accuracy and stability resulting a growing number research groups developing clocks. While good review papers covering topic already...
We present the design and characterisation of a low-noise, resonant input transimpedance amplified photodetector. The device operates at resonance frequency $90 \,\textrm{MHz}$ exhibits an referred current noise $1.2\,\textrm{pA}/\sqrt{\textrm{Hz}}$---marginally above theoretical limit $1.0\,\textrm{pA}/\sqrt{\textrm{Hz}}$ set by room temperature Johnson detector's $16\,\textrm{k}\Omega$ transimpedance. As result, photodetector allows for shot-noise limited operation powers exceeding...
There has been tremendous progress in the performance of optical frequency standards since first proposals to carry out precision spectroscopy on trapped, single ions 1970s. The estimated fractional uncertainty today's leading is currently $10^{-18}$ range, approximately two orders magnitude better than that best caesium primary standards. This exceptional accuracy and stability resulting a growing number research groups developing clocks. While good review papers covering topic already...
Quantum non-demolition (QND) measurement is a remarkable tool for the manipulation of quantum systems. It allows specific information to be extracted while still preserving fragile observables system. Here we apply cavity-based QND an optical lattice clock---a type atomic clock with unrivalled frequency precision---preserving coherence atoms after readout 80\% fidelity. We this technique stabilise phase ultrastable laser coherent state via series repeated measurements. exploit improved...
Abstract We describe a method of duty cycle engineering in optical lattice clocks to reduce clock instability through tailoring the Dick effect noise contribution. apply dynamically decoupled interrogation sequences realise an estimated improvement single approaching factor two, as well providing route zero dead-time operation for two interleaved which are otherwise unable reach required cycle. show simulations and synchronous measurements NPL-Sr1 NPL-Sr2 that quantum projection limited <...