Surface-electrode Ion Trap Research Articles

Electrostatics of gapped and finite surface electrodes

We present approximate methods for calculating the three-dimensional electric potentials of finite surface electrodes including gaps between electrodes, and estimate the effects of finite electrode thickness and an underlying dielectric substrate. As an example, we optimize a radio-frequency surface-electrode ring ion trap, and find that each of these factors reduces the trapping secular frequencies by less than 5% in realistic situations. This small magnitude validates the usual assumption of neglecting the influences of gaps between electrodes and the finite electrode extent.

Individual addressing of ions using magnetic field gradients in a surface-electrode ion trap

A dense array of ions in microfabricated traps represents one possible way to scale up ion trap quantum computing. The ability to address individual ions is an important component of such a scheme. We demonstrate individual addressing of trapped ions in a microfabricated surface-electrode trap using a magnetic field gradient generated on-chip. A frequency splitting of 310(2) kHz for two ions separated by 5 μm is achieved. Selective single qubit operations are performed on one of two trapped ions with an average of 2.2(±1.0%) crosstalk. Coherence time is reduced by the magnetic field gradient, but the spin-echo technique effectively restores the coherence time.

Temperature Dependence of Electric Field Noise above Gold Surfaces

Electric field noise from fluctuating patch potentials is a significant problem for a broad range of precision experiments, including trapped ion quantum computation and single spin detection. Recent results demonstrated strong suppression of this noise by cryogenic cooling, suggesting an underlying thermal process. We present measurements characterizing the temperature and frequency dependence of the noise from 7 to 100 K, using a single Sr+ ion trapped 75 mum above the surface of a gold plated surface electrode ion trap. The noise amplitude is observed to have an approximate 1/f spectrum around 1 MHz, and grows rapidly with temperature as T;{beta} for beta from 2 to 4. The data are consistent with microfabricated cantilever measurements of noncontact friction but do not extrapolate to the dc measurements with neutral atoms or contact potential probes.

Laser ablation loading of a surface-electrode ion trap

We demonstrate loading of $^{88}\mathrm{Sr}^{+}$ ions by laser ablation into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of $1--10\phantom{\rule{0.3em}{0ex}}\mathrm{mJ}$ and durations of $4\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth $(40\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$ below where electron impact ionization loading is typically successful $(\ensuremath{\gtrsim}500\phantom{\rule{0.3em}{0ex}}\mathrm{meV})$.