D. J. Wineland

Microfabricated surface-electrode ion trap for scalable quantum information processing.

Individual laser-cooled 24Mg+ ions are confined in a linear Paul trap with a novel geometry where gold electrodes are located in a single plane and the ions are trapped 40 microm above this plane. The relatively simple trap design and fabrication procedure are important for large-scale quantum information processing (QIP) using ions. Measured ion motional frequencies are compared to simulations. Measurements of ion recooling after cooling is temporarily suspended yield a heating rate of approximately 5 motional quanta per millisecond for a trap frequency of 2.83 MHz, sufficiently low to be useful for QIP.

Observation of theS01→P03Clock Transition inAl+27

We report, for the first time, laser spectroscopy of the 1S0-->3P0 clock transition in 27Al+. A single aluminum ion and a single beryllium ion are simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb repulsion. This coupling allows the beryllium ion to sympathetically cool the aluminum ion and also enables transfer of the aluminums electronic state to the berylliums hyperfine state, which can be measured with high fidelity. These techniques are applied to measure the clock transition frequency nu=1,121,015,393,207,851(6) Hz. They are also used to measure the lifetime of the metastable clock state tau=20.6+/-1.4 s, the ground state 1S0 g factor gS=-0.000,792,48(14), and the excited state 3P0 g factor gP=-0.001,976,86(21), in units of the Bohr magneton.

Single-qubit-gate error below10−4in a trapped ion

With a {sup 9}Be{sup +} trapped-ion hyperfine-state qubit, we demonstrate an error probability per randomized single-qubit gate of 2.0(2)x10{sup -5}, below the threshold estimate of 10{sup -4} commonly considered sufficient for fault-tolerant quantum computing. The {sup 9}Be{sup +} ion is trapped above a microfabricated surface-electrode ion trap and is manipulated with microwaves applied to a trap electrode. The achievement of low single-qubit-gate errors is an essential step toward the construction of a scalable quantum computer.

Efficient fiber optic detection of trapped ion fluorescence.

Integration of fiber optics may play a critical role in the development of quantum information processors based on trapped ions and atoms by enabling scalable collection and delivery of light and coupling trapped ions to optical microcavities. We trap 24Mg+ ions in a surface-electrode Paul trap that includes an integrated optical fiber for detecting 280-nm fluorescence photons. The collection numerical aperture is 0.37, and total collection efficiency is 2.1%. The ion can be positioned between 80 and 100 μm from the tip of the fiber by use of an adjustable rf pseudopotential.

Trapped-Ion State Detection through Coherent Motion

We demonstrate a general method for state detection of trapped ions that can be applied to a large class of atomic and molecular species. We couple a spectroscopy ion (27Al+) to a control ion (25Mg+) in the same trap and perform state detection through off-resonant laser excitation of the spectroscopy ion that induces coherent motion. The motional amplitude, dependent on the spectroscopy ion state, is measured either by time-resolved photon counting or by resolved sideband excitations on the control ion. The first method provides a simplified way to distinguish clock states in 27Al+, which avoids ground-state cooling and sideband transitions. The second method reduces spontaneous emission and optical pumping on the spectroscopy ion, which we demonstrate by nondestructively distinguishing Zeeman sublevels in the (1)S0 ground state of 27Al+.

Sympathetic Ground State Cooling and Time-dilation Shifts in an 27Al+ Optical Clock

We report on Raman sideband cooling of ^{25}Mg^{+} to sympathetically cool the secular modes of motion in a ^{25}Mg^{+}-^{27}Al^{+} two-ion pair to near the three-dimensional (3D) ground state. The evolution of the Fock-state distribution during the cooling process is studied using a rate-equation simulation, and various heating sources that limit the efficiency of 3D sideband cooling in our system are discussed. We characterize the residual energy and heating rates of all of the secular modes of motion and estimate a secular motion time-dilation shift of -(1.9±0.1)×10^{-18} for an ^{27}Al^{+} clock at a typical clock probe duration of 150xa0ms. This is a 50-fold reduction in the secular motion time-dilation shift uncertainty in comparison with previous ^{27}Al^{+} clocks.

A Mercury-Ion Optical Clock

The SI second is the most accurately realized of the base units, and time intervals can therefore be measured more precisely than any other fundamental quantity. Precision timing information from atomic clocks provides the backbone of such ubiquitous technologies as electrical power grids, wireless phone networks and the global positioning system. Todays best time and frequency standards, cesium fountain atomic clocks, have uncertainty at the level of about two nanoseconds per month. The search for yet more accurate and stable frequency standards has now led to the development of optical-frequency atomic clocks.

Frequency Comparison of Al+ and Hg+ Optical Standards

We compare the frequencies of two single ion frequency standards: Al and Hg . Systematic fractional frequency uncertainties of both standards are below 10, and the statistical measurement uncertainty is below 5× 10. Recent ratio measurements show a reproducibility that is better than 10. Although single-ion optical frequency standards promise a potential accuracy of 10 or better, this long-standing goal has not yet been realized due to various technical difficulties. Here we report progress for the NIST Hg and Al single-ion standards, as their systematic fractional frequency uncertainty approaches 10. In these measurements, the fourth harmonics of two clock lasers are locked to the mercury and aluminum clock transitions at 282 and 267 nm respectively. An octave-spanning self-referenced Ti:Sapphire femtosecond laser frequency comb (FLFC) is phase-locked to one clock laser, and the heterodyne beat-note of the other clock laser with the nearest comb-tooth is measured. The various beat-note and offset frequencies can be combined to yield a frequency ratio, which is independent of the Cs-based definition of the second, allowing this ratio to be measured even more accurately than the fundamental unit of time can be realized. In more recent comparisons of the frequencies of the two clock lasers, an octave-spanning self-referenced fiber comb laser has provided a second independent measure of the frequency ratio.

Observation of the {sup 1}S{sub 0}{yields}{sup 3}P{sub 0} Clock Transition in {sup 27}Al{sup +}

We report, for the first time, laser spectroscopy of the {sup 1}S{sub 0}{yields}{sup 3}P{sub 0} clock transition in {sup 27}Al{sup +}. A single aluminum ion and a single beryllium ion are simultaneously confined in a linear Paul trap, coupled by their mutual Coulomb repulsion. This coupling allows the beryllium ion to sympathetically cool the aluminum ion and also enables transfer of the aluminums electronic state to the berylliums hyperfine state, which can be measured with high fidelity. These techniques are applied to measure the clock transition frequency {nu}=1 121 015 393 207 851(6) Hz. They are also used to measure the lifetime of the metastable clock state {tau}=20.6{+-}1.4 s, the ground state {sup 1}S{sub 0} g factor g{sub S}=-0.000 792 48(14), and the excited state {sup 3}P{sub 0} g factor g{sub P}=-0.001 976 86(21), in units of the Bohr magneton.

Sympathetic cooling of {sup 9}Be{sup +} and {sup 24}Mg{sup +} for quantum logic

We demonstrate the cooling of a two species ion crystal consisting of one