We report the design, fabrication and characterization of a microfabricated surface-electrode ion trap that supports controlled transport through the two-dimensional intersection of linear trapping zones arranged in a 90 • cross. The trap is fabricated with very large scalable integration techniques which are compatible with scaling to a large quantum information processor. The shape of the radio-frequency electrodes is optimized with a genetic algorithm to reduce axial pseudopotential barriers and minimize ion heating during transport. Seventy-eight independent dc control electrodes enable fine control of the trapping potentials. We demonstrate reliable ion transport between junction legs and determine the rate of ion loss due to transport. Doppler-cooled ions survive more than 10 5 round-trip transits between junction legs without loss and more than 65 consecutive round trips without laser cooling.
Abstract. Recent advances in quantum information processing with trapped ions have demonstrated the need for new ion trap architectures capable of holding and manipulating chains of many (>10) ions. Here we present the design and detailed characterization of a new linear trap, microfabricated with scalable complementary metal-oxide-semiconductor (CMOS) techniques, that is well-suited to this challenge. Forty-four individually controlled dc electrodes provide the many degrees of freedom required to construct anharmonic potential wells, shuttle ions, merge and split ion chains, precisely tune secular mode frequencies, and adjust the orientation of trap axes. Microfabricated capacitors on dc electrodes suppress radio-frequency pickup and excess micromotion, while a top-level ground layer simplifies modeling of electric fields and protects trap structures underneath. A localized aperture in the substrate provides access to the trapping region from an oven below, permitting deterministic loading of particular isotopic/elemental sequences via species-selective photoionization. The shapes of the aperture and radio-frequency electrodes are optimized to minimize perturbation of the trapping pseudopotential. Laboratory experiments verify simulated potentials and characterize trapping lifetimes, stray electric fields, and ion heating rates, while measurement and cancellation of spatiallyvarying stray electric fields permits the formation of nearly-equally spaced ion chains.
We present a microfabricated surface-electrode ion trap with a pair of integrated waveguides that generate a standing microwave field resonant with the 171 Yb + hyperfine qubit. The waveguides are engineered to position the wave antinode near the center of the trap, resulting in maximum field amplitude and uniformity along the trap axis. By calibrating the relative amplitudes and phases of the waveguide currents, we can control the polarization of the microwave field to reduce off-resonant coupling to undesired Zeeman sublevels. We demonstrate single-qubit π -rotations as fast as 1 µs with less than 6% variation in Rabi frequency over an 800 µm microwave interaction region. Fully compensating pulse sequences further improve the uniformity of X -gates across this interaction region.
We report here a detailed characterization of the surface chemical states and morphology of polyimide ͑PI͒ films following modifications by plasma treatment and electroless copper deposition. NH 3 and Ar plasma treatments have been successfully used to achieve morphological and chemical modification of the PI surface so that electroless copper plating can occur. The adhesion strength of the electroless copper to the PI surface was measured and correlated with the plasma-induced chemical and physical modifications of the PI surface. The NH 3 plasma causes primarily chemical changes to the PI surface through creation of nitrogen moieties ͑i.e., -NvCϽ͒ on the surface. The Ar plasma treatment brings about mainly physical changes to the surface ͑i.e., surface roughening͒. The combined-plasma treatment ͑Ar plasma followed by NH 3 plasma͒ combines the desirable chemical and physical effects of each treatment, yielding a PI surface with higher roughness for physical anchoring of the copper and surface bonding sites ͑nitrogen and oxygen sites͒. During the electroless copper surface activation step with tin chloride and palladium chloride, tin bonds mainly with the oxygen on the surface, whereas palladium reacts with tin chloride as well as with the surface nitrogen. A direct relationship has been observed between surface palladium concentration and the abundance of the -NvCϽ sites on the surface. This suggests that the nitrogen radicals created during the NH 3 plasma are incorporated into the surface and serve as bonding sites for the palladium. In the subsequent electroless Cu deposition, there was a direct correlation between the palladium surface concentration and Cu coverage. The adhesion strength of the electroless copper to the PI correlated well to the surface modifications and plasma treatment conditions. For the first time, a specific bonding configuration on the PI surface is shown to promote adsorption of palladium, which in turn promotes covalent bonding with Cu. The relative importance of surface roughness and chemical bonding on the adhesion strength is discussed.Electroless metallization of advanced low-k polymers is of great interest for future high-density packaging substrates. Polyimides ͑PI͒ are an important class of polymers with desirable properties for these packaging and interconnect applications. However, PIs are difficult to activate for subsequent electroless metallization via conventional chemical "swell and etch" treatments. 1 These treatments are widely used for activating epoxy substrates and provide excellent adhesion strength between the electroless copper and the epoxy. Adhesion peel strengths on the order of 460 N/m have been reported for Cu on epoxy substrates. 2 Since the conventional swell and etch treatment has been found to be ineffective to activate the PI surface for electroless Cu deposition, several alternative surface treatments have been attempted in order to activate the PI surfaces. In work performed by Okamura et al., 3 a KOH treatment has been used to cleave the imide ring ...
Quantum networking links quantum processors through remote entanglement for distributed quantum information processing and secure long-range communication. Trapped ions are a leading quantum information processing platform, having demonstrated universal small-scale processors and roadmaps for large-scale implementation. Overall rates of ion-photon entanglement generation, essential for remote trapped ion entanglement, are limited by coupling efficiency into single mode fibers and scaling to many ions. Here, we show a microfabricated trap with integrated diffractive mirrors that couples 4.1(6)% of the fluorescence from a 174 Yb + ion into a single mode fiber, nearly triple the demonstrated bulk optics efficiency. The integrated optic collects 5.8(8)% of the π transition fluorescence, images the ion with sub-wavelength resolution, and couples 71(5)% of the collected light into the fiber. Our technology is suitable for entangling multiple ions in parallel and overcomes mode quality limitations of existing integrated optical interconnects.
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