2001-07-14
I wonder how the BWMA would recommend measuring time or any other dimensions
that are extremely large or small, as shown here. Maybe Han can contact
them and ask them.
BTW, did they ever answer the rest of my questions? If, not, it is time to
ask again.
John
Keiner ist hoffnungsloser versklavt als derjenige, der irrt�mlich glaubt
frei zu sein.
There are none more hopelessly enslaved then those who falsely believe they
are free!
Johann Wolfgang von Goethe (1749-1832)
----- Original Message -----
From: "James R. Frysinger" <[EMAIL PROTECTED]>
To: "U.S. Metric Association" <[EMAIL PROTECTED]>
Sent: Saturday, 2001-07-14 12:09
Subject: [USMA:14383] Re: More precise atomic clock
Here's the abstract for the Science article. The article itself is not
available online (yet?).
Jim
Published online July 12, 2001
Submitted on March 29, 2001
Accepted on June 11, 2001
An Optical Clock Based on a Single Trapped 199Hg+ Ion
S. A. Diddams 1*, Th. Udem 2, J. C. Bergquist 1, E. A. Curtis 3, R. E.
Drullinger 1, L. Hollberg 1, W. M. Itano 1, W. D. Lee 1, C. W. Oates 1,
K. R. Vogel , D. J. Wineland 1
1 Time and Frequency Division, National Institute of Standards and
Technology, 325 Broadway, Boulder, CO 80305, USA.
2 Max-Planck-Institut f�r Quantenoptik, Hans-Kopfermann Strasse 1,
85748, Garching, Germany; Time and Frequency Division,
National Institute of Standards and Technology, 325 Broadway, Boulder,
CO 80305, USA.
3 Time and Frequency Division, National Institute of Standards and
Technology, 325 Broadway, Boulder, CO 80305, USA; Department of Physics,
University of Colorado,
Boulder, CO 80309, USA.
* To whom correspondence should be addressed. E-mail:
[EMAIL PROTECTED]
Microwave atomic clocks have been the de facto standards for precision
time and frequency metrology over the past 50 years, finding widespread
use in basic scientific studies, communications, and navigation.
However, with its higher operating frequency, an atomic clock based on
an optical transition can be much more stable. We demonstrate an
all-optical atomic clock referenced to the 1.064-petahertz transition of
a single trapped 199Hg+ ion. A clockwork based on a mode-locked
femtosecond laser provides output pulses at a 1-gigahertz rate that are
phase-coherently locked to the optical frequency. By comparison to a
laser-cooled calcium optical standard, an upper limit for the fractional
frequency instability of 7 � 10?15 is measured in 1 second of
averaging---a value substantially better than that of the world's best
microwave atomic clocks.
Jim Elwell wrote:
>
> The article below talks about a new clock being more "precise,"
> but everything in it refers to a smaller "tick" interval. What
> use is a finer tick interval if its fundamental accuracy is no
> better, or perhaps even worse?
>
> Jim
....
--
Metric Methods(SM) "Don't be late to metricate!"
James R. Frysinger, CAMS http://www.metricmethods.com/
10 Captiva Row e-mail: [EMAIL PROTECTED]
Charleston, SC 29407 phone/FAX: 843.225.6789
