Warren Nagourney

Optical clocks based on ultranarrow three-photon resonances in alkaline earth atoms

A sharp resonance line that appears in three-photon transitions between the 1S0 and 3P0 states of alkaline earth and Yb atoms is proposed as an optical frequency standard. This proposal permits the use of the even isotopes, in which the clock transition is narrower than in proposed clocks using the odd isotopes and the energy interval is not affected by external magnetic fields or the polarization of trapping light. With this method, the width and the rate of the clock transition can, in principle, be continuously adjusted from the MHz level to sub-mHz without loss of signal amplitude by varying the intensities of the three optical beams. Doppler and recoil effects can be eliminated by proper alignment of the three optical beams or by point confinement in a lattice trap. Light-shift effects on the clock accuracy can be limited to below a part in 10(18).

Demonstration of new Paul–Straubel trap for trapping single ions

New Paul–Straubel traps [H. Straubel, Naturwissenschaften 18, 506 (1955)] have been recently constructed and used to trap single Ba+ ions. Unlike a conventional rf trap, these traps use only a ring electrode surrounded by an uncritical ground electrode structure. The overall simplicity makes it easy to miniaturize the trap and to control the trapping potential spatial orientation. The new design also allows intense heating of the ring electrode with an ion in the trap simply by passing a large current through it. This removes surface layers responsible for large contact potentials varying over the ring surface and greatly reduces the forced micromotion of the ion, which is supposedly ‘‘at rest.’’

Radio frequency spectroscopy with a trapped Ba+ ion: recent progress and prospects for measuring parity violation

We have employed the method of shelving to measure Zeeman resonances of a single trapped Ba+ ion in low magnetic fields, and have observed radio frequency transitions with linewidths of 5 Hz, limited by magnetic-field noise. We have also observed the shift in the Zeeman frequency when the ion is illuminated by off-resonant light. A simultaneous measurement of such light shifts in two atomic states of Ba+ will permit a precise determination of the ratio of transition matrix elements. Furthermore, using this method with an ion in a standing lightwave, a proposed parity nonconservation (PNC) measurement with Ba+ or Ra+ could be realized. In this paper we review methods and the status of these experiments and discuss the remaining challenges of the PNC experiment.

High resolution Ba+ monoion spectroscopy with frequency stabilized color-center laser

Abstract We describe an experiment in which a stabilized color-center laser is used to perform high resolution spectroscopy on single, laser-cooled barium ions. Virtually every transition between the two levels of interest was observed using the “shelved-optical electron” double resonance technique. Detailed error signal analyses show a 4.8 kHz rms laser linewidth relative to the reference cavity. The absolute laser linewidth can be determined from the single ion spectrum, where the single ion can be viewed as an extremely narrow, stable spectrum analyzer. Correcting for slow cavity drift, an rms laser linewidth of ≃ 13 kHz over a 10 s observation period is obtained. We believe that the observed absolute laser with is principally limited by short term fluctuations in the reference cavity.

Precision Measurement of Light Shifts in a Single Trapped Ba^+ Ion

Experimental tests of atomic theory often involve the measurement of atomic state lifetimes, oscillator strengths, polarizabilities [1], and other properties which depend directly on atomic dipole matrix elements. Absolute measurements of these quantities can be difficult. Another approach [2] is to make high precision measurements of properties which can be directly calculated using modern atomic theory techniques and depend on ratios of atomic matrix elements. Here we report a 0.1% measurement of the ratio R of the ac Stark effect (or light shift) in the 6S1/2 and 5D3/2 states of a singly-ionized barium ion, iso-electronic to the well-studied alkali atom Cs. Comparison of this result with an ab initio calculation of R would yield a new test of atomic theory. Since R is expressible as ratios of matrix elements (shown below), this measurement also establishes a sum rule relating the barium matrix elements known to ∼ 1% or better (i.e. h 6S1/2||r||6P1/2,3/2i ) to matrix ele

Observation of the 1S0-3P0 transition in atomic ytterbium for optical clocks and qubit arrays

We report an observation of the weak 6 1S0-6 3P0 transition in (171,173)Yb as an important step to establishing Yb as a primary candidate for future optical frequency standards, and to open up a new approach for qubits using the 1S0 and 3P0 states of Yb atoms in an optical lattice.

Progress on indium and barium single ion optical frequency standards

We report progress on /sup 115/In/sup +/ and /sup 137/Ba/sup +/ single ion optical frequency standards using all solid-state sources. Both are free from quadrupole field shifts and together enable a search for drift in fundamental constants.

Analysis of Paul–Straubel trap and its variations

Unconventional rf traps of the Paul–Straubel type and its variations have found increasing use in ion trapping experiments. Calculations of the properties of these traps are presented. Simple realistic trap geometries are studied for their voltage loss factor, anharmonicity, and radial symmetry breaking. Optimum geometries for these traps are indicated.

Measurement of light shifts at two off-resonant wavelengths in a single trapped Ba+ ion and the determination of atomic dipole matrix elements

We define and measure the ratio (R) of the vector ac-Stark effect (or light shift) in the 6S_1/2 and 5D_3/2 states of a single trapped barium ion to 0.2% accuracy at two different off-resonant wavelengths. We earlier found R = -11.494(13) at 514.531nm and now report the value at 1111.68nm, R = +0.4176(8). These observations together yield a value of the matrix element, previously unknown in the literature. Also, comparison of our results with an ab initio calculation of dynamic polarizability would yield a new test of atomic theory and improve the understanding of atomic structure needed to interpret a proposed atomic parity violation experiment.

Tunable cavity coupling scheme using a wedged plate

We describe a novel scheme for tuning the input coupling of an optical resonator. This scheme employs a wedged plate which is slightly reflective rather than the more conventional slightly transmissive element.