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51.
52.
Laser cooling to the zero-point energy of motion 总被引:1,自引:0,他引:1
53.
54.
A capillary gas chromatography-mass spectrometry for analysis of 15N-labeled amino acids and amides is described. The method is based on direct silylation of amino acids and amides with MTBSTFA and the formation of the TBDMS derivatives. The method was possible simultaneously to measure the 15N abundance ratio of amino-N and amide-N of amides, as to analysis of amino acids. 相似文献
55.
Schaetz T Barrett MD Leibfried D Britton J Chiaverini J Itano WM Jost JD Knill E Langer C Wineland DJ 《Physical review letters》2005,94(1):010501
We investigate theoretically and experimentally how quantum state-detection efficiency is improved by the use of quantum information processing (QIP). Experimentally, we encode the state of one 9Be(+) ion qubit with one additional ancilla qubit. By measuring both qubits, we reduce the state-detection error in the presence of noise. The deviation from the theoretically allowed reduction is due to infidelities of the QIP operations. Applying this general scheme to more ancilla qubits suggests that error in the individual qubit measurements need not be a limit to scalable quantum computation. 相似文献
56.
WM. Hayden Smith 《Optical and Quantum Electronics》1972,4(2):161-167
The Fabry-Perot interferometer can be used as a periodic filter for the sorting of spectra using the rotational Raman effect. Thus it is possible to detect low concentrations of impurities in the presence of the major atmospheric constituents. The parameters of importance in making these measurements and the expected results from this technique are discussed from theoretical computations. 相似文献
57.
Absolute frequency measurements of the Hg+ and Ca optical clock transitions with a femtosecond laser
Udem T Diddams SA Vogel KR Oates CW Curtis EA Lee WD Itano WM Drullinger RE Bergquist JC Hollberg L 《Physical review letters》2001,86(22):4996-4999
The frequency comb created by a femtosecond mode-locked laser and a microstructured fiber is used to phase coherently measure the frequencies of both the Hg+ and Ca optical standards with respect to the SI second. We find the transition frequencies to be f(Hg) = 1 064 721 609 899 143(10) Hz and f(Ca) = 455 986 240 494 158(26) Hz, respectively. In addition to the unprecedented precision demonstrated here, this work is the precursor to all-optical atomic clocks based on the Hg+ and Ca standards. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of the absolute value of( partial differential f(Ca)/ partial differential t)/f(Ca) < or =8 x 10(-14) yr(-1) and the absolute value of(partial differential f(Hg)/ partial differential t)/f(Hg) < or =30 x 10(-14) yr(-1). 相似文献
58.
Kimmo A Michelsen Daniël LA van den Hove Christoph Schmitz Olivier Segers Jos Prickaerts Harry WM Steinbusch 《BMC neuroscience》2007,8(1):107
Background
Both prenatal stress (PS) and postnatal chronic mild stress (CMS) are associated with behavioral and mood disturbances in humans and rodents. The aim of this study was to reveal putative PS- and/or CMS-related changes in basal spine morphology and density of pyramidal neurons in the rat medial prefrontal cortex (mPFC). 相似文献59.
J.E. Stalnaker S.A. Diddams T.M. Fortier K. Kim L. Hollberg J.C. Bergquist W.M. Itano M.J. Delany L. Lorini W.H. Oskay T.P. Heavner S.R. Jefferts F. Levi T.E. Parker J. Shirley 《Applied physics. B, Lasers and optics》2007,89(2-3):167-176
We report the technical aspects of the optical-to-microwave comparison for our recent measurements of the optical frequency
of the mercury single-ion frequency standard in terms of the SI second as realized by the NIST-F1 cesium fountain clock. Over
the course of six years, these measurements have resulted in a determination of the mercury single-ion frequency with a fractional
uncertainty of less than 7×10-16, making it the most accurately measured optical frequency to date. In this paper, we focus on the details of the comparison
techniques used in the experiment and discuss the uncertainties associated with the optical-to-microwave synthesis based on
a femtosecond laser frequency comb. We also present our most recent results in the context of the previous measurements of
the mercury single-ion frequency and arrive at a final determination of the mercury single-ion optical frequency: f(Hg+)=1 064 721 609 899 145.30(69) Hz.
PACS 06.30.Ft; 42.62.Eh; 32.30.Jc 相似文献
60.
Fortier TM Ashby N Bergquist JC Delaney MJ Diddams SA Heavner TP Hollberg L Itano WM Jefferts SR Kim K Levi F Lorini L Oskay WH Parker TE Shirley J Stalnaker JE 《Physical review letters》2007,98(7):070801
We report tests of local position invariance and the variation of fundamental constants from measurements of the frequency ratio of the 282-nm 199Hg+ optical clock transition to the ground state hyperfine splitting in 133Cs. Analysis of the frequency ratio of the two clocks, extending over 6 yr at NIST, is used to place a limit on its fractional variation of <5.8x10(-6) per change in normalized solar gravitational potential. The same frequency ratio is also used to obtain 20-fold improvement over previous limits on the fractional variation of the fine structure constant of |alpha/alpha|<1.3x10(-16) yr-1, assuming invariance of other fundamental constants. Comparisons of our results with those previously reported for the absolute optical frequency measurements in H and 171Yb+ vs other 133Cs standards yield a coupled constraint of -1.5x10(-15)相似文献