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arXiv:2608.04681

Field Deviations in Dipole-Driven Linear Paul Traps: Effects of Endcap Boundaries and their Minimization

Vaibhav Mahendrakar, Nishant Joshi, S. A. Rangwala

Published Aug 5, 2026• 0 citations
arXivHTMLPDF

Abstract

Deviations from both the ideal linear Paul trap (LPT) geometry as well as the ideal quadrupole driving scheme introduce imperfections to ion trapping potentials. We investigate the effects of these imperfections in a LPT operated in a conventional dipole-drive configuration. We demonstrate the trapping of the Li$^+$ ions along the axial direction with zero and negative end-cap voltages. This occurs due to the modified axial $a-q$ space resulting from radial-to-axial coupling of the electric field. The dipole drive configuration lifts the degeneracy of the radial trapping potentials, resulting in unequal radial secular frequencies, and this is demonstrated experimentally. The combined effects of dipole drive and trap dimensions are summarized in a two-dimensional map that quantifies deviations from ideal behaviour. Based on this map, we propose a geometric modification that significantly reduces radial-to-axial coupling of the potential.

DOI
10.48550/arxiv.2608.04681

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Deviations from both the ideal linear Paul trap (LPT) geometry as well as the ideal quadrupole driving scheme introduce imperfections to ion trapping potentials. We investigate the effects of these imperfections in a LPT operated in a conventional dipole-drive configuration. We demonstrate the trapping of the Li+^++ ions along the axial direction with zero and negative end-cap voltages. This occurs due to the modified axial a−qa-qa−q space resulting from radial-to-axial coupling of the electric field. The dipole drive configuration lifts the degeneracy of the radial trapping potentials, resulting in unequal radial secular frequencies, and this is demonstrated experimentally. The combined effects of dipole drive and trap dimensions are summarized in a two-dimensional map that quantifies deviations from ideal behaviour. Based on this map, we propose a geometric modification that significantly reduces radial-to-axial coupling of the potential.
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In this work, we present the design, construction, and characterization of a linear Paul trap in a blade configuration. The trap was optimized to minimize micromotion and enable the formation of linear ion chains comprising tens of ions. We discuss the design requirements for low axial micromotion and reduced capacitance and describe the simulation and optimization of the trap design parameters. The assembled trap is characterized through direct measurements of the axial and radial confinement frequencies using the tickling method. We identify deviations from the target design due to manufacturing tolerances and present a compensation procedure to calibrate and correct for these effects.
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A linear radio-frequency Paul trap is traditionally driven with one diagonal pair of electrodes grounded and the other connected to a high-voltage radio-frequency source. This method simplifies impedance matching of the voltage source to the trap. However, for several architectures it leads to increasing the axial micromotion amplitude, for example, when the capacitance between radio-frequency and end-cap electrodes is not negligible. Here, we present a technique to generate two high-voltage radio-frequency signals \SI{180}{\degree} out of phase to drive a linear Paul trap with opposite voltages between neighbouring electrodes. Using this, we have successfully trapped and cooled a chain of Ytterbium ions in a linear radio-frequency Paul trap.
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