Characterization of Inner Control Electrode Shapes for Multi-Layer Surface-Electrode Ion Traps

Abstract

Microfabricated surface-electrode traps are a scalable platform for trapped-ion quantum processors. Recent advances in fabrication techniques have enabled the design of increasingly complex multi-layer structures. Yet the control electrodes remain mostly unchanged and of rectangular shape. We systematically analyze asymmetric inner control electrode shapes for simultaneous axial and radial control in multi-layer surface traps, characterize and compare a selection of different shapes, and verify their capabilities in realistic use-case scenarios for ion transport and micromotion compensation. Eliminating the need for the commonly used additional outer control electrodes, asymmetric inner control electrodes increase the compactness and space efficiency of surface-electrode traps while concurrently reducing the number of control signals. The improved control voltage efficiency of using solely inner electrodes enables the device's entire direct-current (DC) supply to be provided by integrated Cryo-CMOS circuits, further enhancing the scalability of the processor.

Figures (6)

• Figure 1: A common five-wire surface electrode trap with symmetric RF electrodes (blue), rectangular inner control electrodes (gray) and additional outer control electrodes (light blue) for radial control.
• Figure 2: Surface electrode trap layout with a) axial and radial segmented rectangular, b) triangular, c) rhomboid, d) 'L'-shaped, e) 'T'-shaped, and f) 'Z'-shaped inner control electrodes for simultaneous control in axial and radial directions. No additional outer control electrodes are required for radial control. The RF electrodes are shown in blue and the white area outside the RF is ground.
• Figure 3: Normalized electric potential $\hat{\varphi}_{\rm{st}}$ for the different inner control electrode shapes held at $-1\,\rm{V}$ relative to the electrodes center located at $x'=0~\rm{ \mu m}$. For reference the potential corresponding to the rectangular inner DC electrode in Figure \ref{['fig: inner rect dc']} is shown as the gray-dashed line. Note that the area $A_{\rm{DC}}$ of the rectangular electrode is double that of the other electrode shapes, resulting in twice the electric potential ($\hat{\varphi}_{\rm{st}} \sim A_{\rm{DC}}$).
• Figure 4: First order derivatives of the normalized electric potential $\partial_i \, \hat{\varphi}_{\rm{st}}$ along the a) $x$-direction, b) $y$-, and c) $z$-direction for the different inner control electrode shapes held at $-1\,\rm{V}$ relative to the electrodes center located at $x'=0~\rm{ \mu m}$. The potentials' derivatives corresponding to the rectangular inner control electrode in Figure \ref{['fig: inner rect dc']} are shown as the gray-dashed line for comparison. Due to its symmetry with respect to the $y$-axis the potential derivative $\partial_y \, \hat{\varphi}_{\rm{st}}$ along this direction is zero.
• Figure 5: Second order derivatives of the normalized electric potential $\partial_i^{\,2} \, \hat{\varphi}_{\rm{st}}$ along the principal axis $\rm{tr}(H(\hat{\varphi}_{\rm{st}}))$ for the different inner control electrode shapes held at $-1\,\rm{V}$ relative to the electrodes center located at $x'=0~\rm{ \mu m}$. The potential's derivatives corresponding to the rectangular inner control electrode in Figure \ref{['fig: inner rect dc']} are shown as gray-dashed lines for reference.