Quantum coherence between two atoms beyond Q=10(15).

We place two atoms in quantum superposition states and observe coherent phase evolution for 3.4×10(15) cycles. Correlation signals from the two atoms yield information about their relative phase even after the probe radiation has decohered. This technique allowed a frequency comparison of two (27)Al(+) ions with fractional uncertainty 3.7(-0.8)(+1.0)×10(-16)/√[τ/s]. Two measures of the Q factor are reported: The Q factor derived from quantum coherence is 3.4(-1.1)(+2.4)×10(16), and the spectroscopic Q factor for a Ramsey time of 3 s is 6.7×10(15). We demonstrate a method to detect the individual quantum states of two Al(+) ions in a Mg(+)-Al(+)-Al(+) linear ion chain without spatially resolving the ions.

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+.

Further development of the high volume air sampler for high resistance filter media.

The high volume air sampler is the only instrument that has been continuously successful over the last twenty years in measuring ambient concentrations of total suspended particulate (TSP). For several years, efforts have been made to rectify the artifact problems arising from the use of glass fiber filters with this sampler. The artifacts chiefly involve the reaction of sulfate and nitrate compounds with the filter paper. Other substrates have been tried, but not successfully applied, because of their higher resistance to flow. A new blower motor permits the use of all existing sampler accessories, including the flow controller. Numerous substrates have been tested to compare their capacities relevant to glass fiber paper. Tests have been run to the performance limit of the fan, with results being normalized to 24 hours.