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arXiv:2602.19588 · Scientific Reports

Characterization and active cancellation of power-line-induced motional-mode frequency noise in a trapped-ion system

Jaehun You, Jiyong Kang, Kyunghye Kim, Wonhyeong Choi, Taehyun Kim

quant-phSubmitted Feb 23, 2026• Announced Feb 24, 2026• 0 citations
v1 · Feb 23, 2026v2 · Jun 22, 2026
arXivHTMLPDF

Abstract

The stability of motional-mode frequency is essential for realizing high-fidelity quantum gates in trapped-ion quantum computing. While broadband Gaussian noise has been extensively studied and mitigated using pulse shaping techniques, the impact of coherent periodic noise has remained largely unexplored. Here we report a systematic investigation of 60-Hz power-line noise and its effect on the secular frequencies of a single ${}^{171}\mathrm{Yb}^{+}$ ion. Using spin-echo Ramsey spectroscopy, we characterize the amplitude and phase of the resulting secular-frequency modulation and validate this characterization via passive phase correction of the Ramsey sequence. Building on this, we implement active cancellation by injecting a compensation tone into the set-point of a PI controller that stabilizes the trap RF drive amplitude. A phasor-fitting procedure optimizes the amplitude and phase of the compensation signal, enabling near-complete suppression of the 60-Hz component. With active cancellation engaged, the coherence time of a radial motional mode is extended from approximately 10 ms to 35 ms, consistent with the limit set by motional heating. Our results provide both a clear characterization of periodic motional-mode noise and a practical framework for its suppression in trapped-ion quantum computing platforms.

Journal reference
Sci Rep 16, 18474 (2026)
DOI
10.1038/s41598-026-49820-5
Comments
Main text: 8 pages, 4 figures; Supplementary: 6 pages, 3 figures

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Abstract The low-frequency magnetic field noise resulting from the lab[1]oratory power supply is one of the main decoherence sources of trapped-ion qubits. Synchronizing the experimental sequence to the phase of the power line is widely used to mitigate this problem, but it will greatly reduce the ex[1]perimental efficiency. In this paper, we experimentally demonstrate a simple active compensation method to reduce the observed 50 Hz and 150 Hz strong magnetic noise in an ion trap induced by the power line. In our method, a single 40Ca+ ion is used as the noise probe and an reverse compensation sig[1]nal is generated by a programmable arbitrary waveform generator (AWG).After compensation, an 86% reduction of the periodic magnetic field fluc[1]tuation and over 35-fold extension of the coherence time from 70 µs to 2500 µs were observed. This method can also be applied to compensate other spectral components of the magnetic field noise related to the power line, and it is also useful for other atomic systems such as neutral atoms.
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Coherently displaced number states of a harmonically bound ion can be coupled to two internal states of the ion by a laser-induced motional sideband interaction. The internal states can subsequently be read out in a projective measurement via state-dependent fluorescence, with near-unit fidelity. This leads to a rich set of line shapes when recording the internal-state excitation probability after a sideband excitation, as a function of the frequency detuning of the displacement drive with respect to the ion's motional frequency. We precisely characterize the coherent displacement based on the resulting line shapes, which exhibit sharp features that are useful for oscillator frequency determination from the single quantum regime up to very large coherent states with average occupation numbers of several hundred. We also introduce a technique based on multiple coherent displacements and free precession for characterizing noise on the trapping potential in the frequency range of 500 Hz–400 kHz. Signals from the ion are directly used to find and eliminate sources of technical noise in this typically unaccessed part of the spectrum.
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We investigate high frequency motional states of trapped atomic ions. Trapped ions in rf traps are confined by an approximate harmonic potential and exhibit quantum motional states that mediate essential techniques in quantum computing, simulation, networking, and precision measurement. However, motional state decoherence mechanisms, heating and dephasing, are broadly limiting: reduced two-qubit gate fidelities; lower fidelity and lifetime of highly nonclassical bosonic states; long laser cooling times; and large recoil heating rates. These also challenge the scalability of increasingly sophisticated protocols. We propose high motional frequency ion trapping as an operating regime that addresses these challenges and reshapes the design landscape for quantum information experiments and quantum control techniques. We report an experimentally motivated investigation of realizing this high-frequency regime and discuss the consequences for laser cooling, motional state coherence, fidelity and lifetime of nonclassical bosonic states, and scalability of experimental runtimes. We report clear design trajectories for ion traps to reach high motional frequency, a new limiting mechanism for laser cooling at these high frequencies, and more than an order-of-magnitude speedup in experimental duty cycles with larger speed ups possible for quantum error correction protocols. Taken together, high motional frequency ion trapping has broad implications for the future of quantum information experiments.