James C. Bergquist

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The development of atomic frequency standards at NIST is discussed and three of the key frequency-standard technologies of the current era are described. For each of these technologies, the most recent NIST implementation of the particular type of standard is described in greater detail. The best relative standard uncertainty achieved to date for a NIST(More)
We use femtosecond laser frequency combs to convert optical frequency references to the microwave domain, where we demonstrate the synthesis of 10-GHz signals having a fractional frequency instability of < or =3.5 x 10(-15) at a 1-s averaging time, limited by the optical reference. The residual instability and phase noise of the femtosecond-laser-based(More)
Time has always had a special status in physics because of its fundamental role in specifying the regularities of nature and because of the extraordinary precision with which it can be measured. This precision enables tests of fundamental physics and cosmology, as well as practical applications such as satellite navigation. Recently, a regime of operation(More)
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(More)
We present a general technique for precision spectroscopy of atoms that lack suitable transitions for efficient laser cooling, internal state preparation, and detection. In our implementation with trapped atomic ions, an auxiliary "logic" ion provides sympathetic laser cooling, state initialization, and detection for a simultaneously trapped "spectroscopy"(More)
After 50 years of development, microwave atomic clocks based on cesium have achieved fractional uncertainties below 1 part in 10(15), a level unequaled in all of metrology. The past 5 years have seen the accelerated development of optical atomic clocks, which may enable even greater improvements in timekeeping. Time and frequency standards with various(More)
Simulating a quantum computer requires vast computational and processing resources due to the exponential nature of quantum mechanics. Simulating a detailed model like the Cirac and Zoller trapped ion scheme adds further to this complexity. In this paper we define a less complex model which accurately models the trapped ion quantum computer. This model(More)
A single laser-cooled and trapped 9 Be + ion is used to investigate methods of coherent quantum-state synthesis and quantum logic. We create and characterize non-classical states of motion including 'Schrödinger-cat' states. A fundamental quantum logic gate is realized which uses two states of the quantized ion motion and two ion internal states as qubits.(More)
We briefly discuss recent experiments on quantum information processing using trapped ions at NIST. A central theme of this work has been to increase our capabilities in terms of quantum computing protocols, but we have also applied the same concepts to improved metrology, particularly in the area of frequency standards and atomic clocks. Such work may(More)
Testing the stability of fundamental constants with the 199 Hg + single-ion optical clock Over a two-year duration, we have compared the frequency of the 199 Hg + 5d 10 6s 2 S 1/2 (F = 0) ←→ 5d 9 6s 2 2 D 5/2 (F = 2) electric-quadrupole transition at 282 nm with the frequency of the ground-state hyperfine splitting in neutral 133 Cs. These measurements show(More)