Experimental Bayesian Calibration of Trapped-Ion Entangling Operations

Lukas, Gerster,; Martínez-García, Fernando; Hrmo, Pavel; Mourik, Martin W. van; Wilhelm, Benjamin; Vodola, Davide; Müller, Markus; Blatt, R.; Schindler, Philipp; Monz, Thomas

doi:10.1103/prxquantum.3.020350

Cited by 12 publications

(4 citation statements)

References 75 publications

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“…Even after analyzing every existing trade off and finding the optimally efficient protocol, the characterization-experiment time for longer ion chains can still take a significant portion of a typical trapped-ion system's operation cycle. To save the experiment time as much as possible, clever calibration techniques, such as using Bayesian inference [20], can be combined with this work.…”

Section: Discussionmentioning

confidence: 99%

“…Our choice is motivated by the fact that these parameters play a crucial role in both the design and execution of entangling gate operations [13][14][15][16][17][18], one of the most apparent limiting factors for larger-scale trapped-ion quantum computing from both the fidelity and speed aspects. An efficient and accurate mode-parameter characterization can provide significant benefits, such as removing unnecessary overhead in gate calibrations that arise from incorrect parameter estimates [19,20], enabling judicious use of hardware resources that can then be traded off for faster or more robust entangling gates [21], and opening the door to a different paradigm of quantum computer maintenance by frequent, low-cost updates to inevitably drifting parameters (see figure 1).…”

Section: Introductionmentioning

confidence: 99%

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Efficient motional-mode characterization for high-fidelity trapped-ion quantum computing

Kang¹,

Liang²,

Li³

et al. 2023

Quantum Sci. Technol.

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To achieve high-fidelity operations on a large-scale quantum computer, the parameters of the physical system must be efficiently characterized with high accuracy. For trapped ions, the entanglement between qubits are mediated by the motional modes of the ion chain, and thus characterizing the motional-mode parameters becomes essential. In this paper, we develop and explore physical models that accurately predict both magnitude and sign of the Lamb-Dicke parameters when the modes are probed in parallel. We further devise an advanced characterization protocol that shortens the characterization time by more than an order of magnitude, when compared to that of the conventional method that only uses mode spectroscopy. We discuss potential ramifications of our results to the development of a scalable trapped-ion quantum computer, viewed through the lens of system-level resource trade offs.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Efficient motional-mode characterization for high-fidelity trapped-ion quantum computing

Kang¹,

Liang²,

Li³

et al. 2023

Quantum Sci. Technol.

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show abstract

“…We here define a calibration as the determination of a parameter by fitting the results of an experiment. We note that more complex calibration techniques exist based on Bayesian estimation [61] or machine learning [62]. Nevertheless, we restrict ourselves to a simpler class of calibrations for the sake of comparing quantum control schemes.…”

Section: Calibration Requirementsmentioning

confidence: 99%

Quantum control methods for robust entanglement of trapped ions

Valahu

Apostolatos

Weidt

et al. 2022

J. Phys. B: At. Mol. Opt. Phys.

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A major obstacle in the way of practical quantum computing is achieving scalable and robust high-fidelity entangling gates. To this end, quantum control has become an essential tool, as it can make the entangling interaction resilient to sources of noise. Nevertheless, it may be difficult to identify an appropriate quantum control technique for a particular need given the breadth of work pertaining to robust entanglement. To this end, we attempt to consolidate the literature by providing a non-exhaustive summary and critical analysis. The quantum control methods are separated into two categories: schemes which extend the robustness to (i) spin or (ii) motional decoherence. We choose to focus on extensions of the σx ⊗ σx Mølmer-Sørensen interaction using microwaves and a static magnetic field gradient. Nevertheless, some of the techniques discussed here can be relevant to other trapped ion architectures or physical qubit implementations. Finally, we experimentally realize a proof-of-concept interaction with simultaneous robustness to spin and motional decoherence by combining several quantum control methods presented in this manuscript.

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“…An accurate characterization of mode parameters can provide several additional benefits as well. First, the overhead in gate calibrations caused by incorrect parameter estimates [8,9] can be reduced. Second, gate pulses can be more efficient in terms of control-signal power, gate duration, and robustness than pulses designed with inaccurate motional-mode parameters [5,6].…”

Section: Introductionmentioning

confidence: 99%

Pulse optimization for high-precision motional-mode characterization in trapped-ion quantum computers

Liang,

Kang,

et al. 2024

Quantum Sci. Technol.

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High-fidelity operation of quantum computers requires precise knowledge of the physical system through characterization. For motion-mediated entanglement generation in trapped ions, it is crucial to have precise knowledge of the motional-mode parameters such as the mode frequencies and the Lamb-Dicke parameters. Unfortunately, the state-of-the-art mode-characterization schemes do not easily render the mode parameters in a sufficiently accurate and efficient fashion for large-scale devices, due to the unwanted excitation of adjacent modes in the frequency space when targeting a single mode, an effect known as the cross-mode coupling. Here, we develop an alternative scheme that leverages the degrees of freedom in pulse design for the characterization experiment such that the effects of the cross-mode coupling is actively silenced. Further, we devise stabilization methods to accurately characterize the Lamb-Dicke parameters even when the mode frequencies are not precisely known due to experimental drifts or characterization inaccuracies. We extensively benchmark our scheme in simulations of a three-ion chain and discuss the parameter regimes in which the shaped pulses significantly outperform the traditional square pulses.

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Experimental Bayesian Calibration of Trapped-Ion Entangling Operations

Cited by 12 publications

References 75 publications

Efficient motional-mode characterization for high-fidelity trapped-ion quantum computing

Efficient motional-mode characterization for high-fidelity trapped-ion quantum computing

Quantum control methods for robust entanglement of trapped ions

Pulse optimization for high-precision motional-mode characterization in trapped-ion quantum computers

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