A5012404445- Advanced Frequency and Time Standards
- Atomic and Subatomic Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Scientific Measurement and Uncertainty Evaluation
- Quantum optics and atomic interactions
- Spectroscopy and Laser Applications
- Advanced Fiber Laser Technologies
- Advanced Electrical Measurement Techniques
- Radioactive Decay and Measurement Techniques
- Cardiovascular Syncope and Autonomic Disorders
- Geophysics and Sensor Technology
- Quantum Information and Cryptography
- Advanced Chemical Physics Studies
- Advancements in PLL and VCO Technologies
- Optical properties and cooling technologies in crystalline materials
- Electron and X-Ray Spectroscopy Techniques
- Atomic and Molecular Physics
- GNSS positioning and interference
- Quantum Mechanics and Applications
- Non-Invasive Vital Sign Monitoring
- Sensor Technology and Measurement Systems
- Photonic and Optical Devices
- Technical Engine Diagnostics and Monitoring
- Engine and Fuel Emissions
- Semiconductor Lasers and Optical Devices
National Physical Laboratory
2012-2023
Durham University
1999-2003
Jagiellonian University
1997-1998
Observatoire de Paris
1996
Institute of Physics
1992-1993
Singly ionized ytterbium, with ultranarrow optical clock transitions at 467 and 436 nm, is a convenient system for the realization of atomic clocks tests present-day variation fundamental constants. We present first direct measurement frequency ratio these two transitions, without reference to cesium primary standard, using same single ion 171Yb+. The absolute frequencies both are also presented, each relative standard uncertainty 6×10(-16). Combining our results those from other...
The frequency of the 5s 2S(1/2)-4d 2D(5/2) electric quadrupole clock transition in a single, trapped, laser-cooled 88Sr+ ion has been measured by using an optical comb referenced to cesium fountain primary standard. is as 444,779,044,095,484.6 (1.5) hertz, with fractional uncertainty within factor 3 that Improvements required obtain cesium-limited measurement are described and expected lead stability reproducibility exceeding
Istituto Elettrotecnico Nazionale Galileo Ferraris (IEN), National Institute of Standards and Technology (NIST), Physical Laboratory (NPL), Laboratoire de Métrologie et d'Essais—Observatoire Paris/Systèmes Référence Temps Espace (OP) Physikalisch-Technische Bundesanstalt (PTB) operate cold-atom based primary frequency standards which are capable realizing the SI second with a relative uncertainty 1 × 10−15 or even below. These institutes performed an intense comparison campaign selected...
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...
We evaluate the distributed cavity phase and microwave lensing frequency shifts, which were two largest sources of uncertainty for NPL-CsF2 cesium fountain clock. report measurements that confirm a detailed theoretical model fields shifts clock they produce. The significantly reduce to $1.1 \times 10^{-16}$. derive shift cylindrical with circular apertures. An analytic result reasonable approximations is given, in addition full calculation indicates $6.2 10^{-17}$. models we report, along...
An accuracy evaluation of the caesium fountain NPL-CsF2 as a primary frequency standard is reported. The device operates with simple one-stage magneto-optical trap source cold atoms. Both uncertainty in and magnitude collision shift are reduced by taking advantage dependence cross section on effective energy an expanding atomic cloud. combined type B (typically 4 × 10−16) dominated estimate due to distributed cavity phase. When operated at single density, short-term fractional instability...
The frequencies of two nominally identical ${}^{88}{\mathrm{Sr}}^{+}$ trapped single ion optical clocks, based on the 674 nm 5$s$ ${}^{2}$${S}_{1/2}$--4$d$ ${}^{2}$${D}_{5/2}$ electric quadrupole clock transition, have been compared over a period nine months. clocks were found to agree within total uncertainty 4 \ifmmode\times\else\texttimes\fi{} 10${}^{\ensuremath{-}17}$, demonstrating that individual are reproducible at 3 10${}^{\ensuremath{-}17}$ level. absolute frequency transition was...
Abstract The detection of variations fundamental constants the Standard Model would provide us with compelling evidence new physics, and could lift veil on nature dark matter energy. In this work, we discuss how a network atomic molecular clocks can be used to look for such unprecedented sensitivity over wide range time scales. This is precisely goal recently launched QSNET project: A measuring stability constants. will include state-of-the-art clocks, but also develop next-generation highly...
An absolute frequency measurement has been made of the 2S1/2–2F7/2 electric octupole transition in a single ion 171Yb+. The implementation diode-based probe laser stabilized to this highly forbidden resulted an improvement more than one order magnitude upon lowest published uncertainty. After correcting for systematic shifts, was determined be 642 121 496 772 646.22 (67) Hz. This corresponds fractional uncertainty 1.0 × 10−15.
A new caesium fountain frequency standard (NPL-CsF1) at the National Physical Laboratory is described. Procedures for evaluation of systematic shifts are presented. The NPL-CsF1 has a short-term stability σy(τ) = 1.4 × 10−13τ−1/2, predominantly due to local oscillator phase noise. accuracy 1 part in 1015 limited by uncertainty shift collisions between cold atoms.
We have observed that the collisional frequency shift in primary caesium fountain clocks varies with clock state population composition and, particular, is zero for a given fraction of $|F=4,{m}_{F}=0⟩$ atoms, depending on initial cloud parameters. present theoretical model explaining our observations. The possibility cancellation implies an improvement performance standards and simplification their operation.
We report the first accuracy evaluation of NRC-FCs2, an atomic fountain clock developed at National Research Council Canada. The short term stability high density is 1.1 × 10−13 1 second averaging time. typical overall fractional type B uncertainty 2.3 10−16. GNSS-based frequency comparisons NRC-FCs2 with SI second, as reported by BIPM over fourteen months, give a difference −2.4(3.7)
We have studied the behavior of cesium atoms cooled in six-beam "gray" optical molasses. Cooling occurs for a laser detuned to blue side $6{S}_{\frac{1}{2}}$, $F=3\ensuremath{\rightarrow}6{P}_{\frac{3}{2}}$, ${F}^{\ensuremath{'}}=2$ transition, and Sisyphus-type effect accumulates states not coupled light. measure minimum temperature 1.1\ifmmode\pm\else\textpm\fi{}0.1 \ensuremath{\mu}K at low atomic density. The typical cooling time is on order 1 ms. A linear dependence versus density found...
NPL operates a system of two primary caesium fountain clocks consisting fully characterised standard NPL-CsF2 together with new NPL-CsF3, which has recently become operational. Both fountains feature single-stage vapour-loaded magneto-optical trap as the source cold atoms and an approximate cancellation potentially large collision frequency shift. As result, collision-shift type-B uncertainty is less than 10-16. Subsequently, more subtle systematic effects, including shifts from distributed...
We report important modifications introduced to the fountain frequency standard NPL-CsF2, both its hardware and operation protocol. First, an additional optical pumping stage has been implemented, which enabled clock state populations be efficiently accumulated increased number of detected atoms by a factor four without affecting loading cooling stages. Second, near collisional shift cancellation point optimized which, together with atom number, led fourfold reduction in averaging time...
We report on the design, assembly, testing, and delivery of a series new cesium fountain primary frequency standards built through commercial scientific collaboration with international users. The based proven National Physical Laboratory solutions, improves reliability, simplicity operation, transportability. complete system consists novel physics package, specially developed optical dedicated electronics for control. present results showing that despite their simplified more compact...
We demonstrate an atomic fountain guided by a far-off resonance laser beam. show that atoms can be launched within the guide without heating, and through small aperture to UHV chamber. The extension continuous operation is discussed.
The results of precision measurements the 87Rb ground-state hyperfine transition frequency, which were conducted at NPL from 2009 to 2013, are reported. resulting measured using NPL's Cs and Rb atomic frequency standards, demonstrates reasonable agreement with most recent reported by LNE-SYRTE.
The preparation of a sample ultra cold caesium atoms in an ${m}_{F}=0$ Zeeman sublevel the $F=3$ ground state is demonstrated, using cooling optical lattice and adiabatic passage. 97% finally detected experiment populate at temperature $300\phantom{\rule{0.3em}{0ex}}\mathrm{nK}$. Microwave spectroscopy used to measure transfer directly its dependence on various experimental parameters. A theoretical model provided estimate upper limit for efficiency multilevel system with nonresonant...
We present the design of Ramsey cavity to be used in refurbished cesium primary frequency standard NPL-CsF1. This is optimized suppress distributed phase shift.
We have employed an intuitive model and 3D Monte Carlo simulations to study the effect of ballistic expansion atomic cloud on collision energies resulting frequency shift in a fountain clock. In particular, we show that relevant for collisions contributing clock correspond temperatures which may be significantly smaller than temperature at launch. Both assumptions predictions our are related realistic parameters operating caesium clocks.