Recent publications

Frequency stabilization of an ultraviolet laser to ions in a discharge
E. W. Streed, T. J. Weinhold, and D. Kielpinski
Appl Phys Lett 93, 071103 (2008)

Abstract: We stabilize an ultraviolet diode laser system at 369.5 nm to the optical absorption signal from Yb+ ions in a hollow-cathode discharge lamp. The error signal for stabilization is obtained by Zeeman spectroscopy of the 3 GHz wide absorption feature. The frequency stability is independently measured by comparison to the fluorescence signal from a laser-cooled crystal of 174Yb+ ions in a linear Paul trap. We measure a frequency fluctuation of 1.7 MHz over 1000 s and a frequency drift of 20 MHz over 7 days. Our method is suitable for use in quantum information processing experiments with trapped ion crystals.


Scalable, Efficient Ion-Photon Coupling With Phase Fresnel Lenses For Large-Scale Quantum Computing
E.W. Streed, B.G. Norton, J.J. Chapman, and D. Kielpinski
Quant Inform Comp 9, 0203 (2009)

Abstract: Efficient ion-photon coupling is an important component for large-scale ion-trap quantum computing. We propose that arrays of phase Fresnel lenses (PFLs) are a favorable optical coupling technology to match with multi-zone ion traps. Both are scalable technologies based on conventional micro-fabrication techniques. The large numerical apertures (NAs) possible with PFLs can reduce the readout time for ion qubits. PFLs also provide good coherent ion-photon coupling by matching a large fraction of an ion’s emission pattern to a single optical propagation mode (TEM00). To this end we have optically characterized a large numerical aperture phase Fresnel lens (NA=0.64) designed for use at 369.5 nm, the principal fluorescence detection transition for Yb+ ions. A diffraction-limited spot w0 = 350 ± 15 nm (1/e2 waist) with mode quality M2 = 1.08 ± 0.05 was measured with this PFL. From this we estimate the minimum expected free space coherent ion-photon coupling to be 0.64%, which is twice the best previous experimental measurement using a conventional multi-element lens. We also evaluate two techniques for improving the entanglement fidelity between the ion state and photon polarization with large numerical aperture lenses.