Controlling trapping potentials and stray electric fields in a microfabricated ion trap through design and compensation

Abstract

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.

Heating rates and ion-motion control in aY-junction surface-electrode trap

“…This agrees well given the assumptions of the motional decoherence model. At our ion-surface distance (∼70 μm), this heating rate, which corresponds to a noise spectral density ωS ∼ 1.2 × 10 −3 V 2 /m 2 , is comparable to other surface-electrode traps at room temperature without surface cleaning and an order of magnitude worse than the best reported heating rates [11].…”

“…For radial motion parallel to the trap surface, we measure micromotion using the rf photon correlation method [35] and by detecting resolved micromotion sidebands on the 397-nm transition [11,21]. For motion perpendicular to the trap surface, we measure the micromotion sidebands of the 4s 2 S 1/2 →3d 2 D 5/2 transition [21].…”

“…This architecture requires an array of electrodes capable of trapping ions at arbitrary locations, shuttling ions through two-dimensional junctions, and merging and splitting ion chains. Surface-electrode ion traps [2][3][4][5][6][7][8][9][10][11][12] are well suited to all of these operations and precise microfabrication allows for complicated and scalable trap electrode geometries. These traps support higher secular frequencies than macroscopic traps and can be outfitted with additional features such as integrated near-side or on-chip optics [13][14][15][16] and microwave control lines [17][18][19].…”

Surface noise analysis using a single-ion sensor

“…In Fig. 5 summarize ω S E versus the closest ion-electrode distance, for a number of trap noise measurements reported in the literature [5,19,20,22,25,[38][39][40][41][42][43]. To compare between ion traps with different dimensions, one scales the noise with ion distance from the surface, d, as S E ∼ d −4 .…”

Spatially uniform single-qubit gate operations with near-field microwaves and composite pulse compensation

“…The trap conforms to a symmetric five-wire surface-electrode Paul trap geometry [23] fabricated on a 11 × 11 mm 2 silicon die (figure 1(a)) similar to the designs reported in [24][25][26]. Electrodes etched into three sputtered aluminum layers are separated by insulating silicon dioxide films.…”