Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Applied Sciences

A Feedback Control Method to Maintain the Amplitude of the RF Signal Applied to Ion Traps

Yunjae Park, Hyunseok Oh, Seung-Woo Yoo, Taehyun Kim, Dong‐il Cho

Published Jan 17, 2021• 3 citations
Publisher

Abstract

For high-fidelity quantum operations in ion traps, it is important to maintain the secular frequency of the trapped ions at a constant value. The radial secular frequency is proportional to the amplitude of the radio frequency (RF) signal applied to ion traps. Owing to the changes in the ambient temperature of a helical resonator and the minute vibration of the optical table, the amplitude can vary. Recently, a method for reducing the fluctuation in the RF signal amplitude, using a commercial universal proportional-plus-integral (PI) controller, has been introduced, which, in turn, reduces the secular frequency drift of the trapped ions. The method improves the capability to maintain the secular frequency at a constant value. However, the structure of the controller is fixed; thus, the control method cannot be changed to suit different experimental conditions, and the different feedback configuration cannot be implemented to increase the resolution. In this paper, we develop a field-programmable gate array (FPGA)-based feedback controller that allows the implementation of various automatic control methods and feedback configurations. In our experiments, the fluctuation in the amplitude of the RF signal was 1.806% using a commercial universal PI controller. The fluctuation was reduced to 0.099% using the developed FPGA-based PI controller, and to 0.102% using the developed FPGA-based lag compensator. By employing the developed FPGA control method, many other automating control methods can be applied to achieve a stable and high-performance control of the secular frequency.

DOI
10.3390/app11020837

Related papers

FPGA-based feedback control of quantum optics experiments with the open source software package PyRPL

Leonhard Neuhaus, M. Croquette, Rémi Metzdorff +8 more

We present PyRPL, an open source software package that allows the implementation of automatic digital feedback controllers for quantum optics experiments on commercially available, affordable FPGA boards. Our software implements the digital generation of various types of error signals, from an analog input through the application of loop filters of high complexity and real-time gain adjustment for multiple analog output signals, including different algorithms for resonance search, lock acquisition sequences and in-loop gain optimization. Furthermore, all necessary diagnostic instruments such as an oscilloscope, a network analyzer and a spectrum analyzer are integrated into our software. Apart from providing a quickly scalable, automatic feedback controller, the lock performance that can be achieved by using PyRPL with imperfect equipment such as piezoelectric transducers and noisy amplifiers is better than the one achievable with standard analog controllers due to the higher complexity of implementable filters and possibilities of nonlinear operations in the FPGA. This drastically reduces the cost of added complexity when introducing additional feedback loops to an experiment. The open-source character also distinguishes PyRPL from commercial solutions, as it allows users to customize functionalities at various levels, ranging from the easy integration of PyRPL-based feedback controllers into existing setups to the modification of the FPGA functionality. A community of developers provides fast and efficient implementation and testing of software modifications.

arXiv:2310.00086•Sep 29, 2023•1 citation

Stabilization of ion-trap secular frequencies for a quantum phase transition study

Jie Zhang, B. T. Chow, P. C. Haljan

An array of ions in a linear radio-frequency (RF) Paul trap is a good candidate for investigating structural phase transitions, such as the linear-to-zigzag (LZ) transition, due to the convenient control provided by modification of the trap confinement strength. In such studies, the trap secular frequencies are a key factor that limits the stability of the critical point (CP). In this paper, we implement secular-frequency stabilization, including active feedback stabilization of the RF voltage near the trap electrodes, and achieve a stability of better than 5~ppm over 200~s for both transverse and axial potentials. To evaluate the combined long-term stability of the trap potential in both directions, we measure the zigzag (ZZ) mode frequency near the CP, where the effect of instability in both trap directions is substantially amplified. The short-term noise within a limited spectral window is also suppressed by this scheme, as inferred from decoherence rates of the ZZ mode measured at different frequencies with Ramsey fringes. We also identify that the limitation of the secular frequency stability is mainly from the imperfect temperature insensitivity of voltage dividers and RF detectors, and as a result improvement of lab temperature stability is of great help for stabilizing the trap frequency.

arXiv:2210.14478•Oct 26, 2022•0 citations

A New Measurement Method for High Voltages Applied to an Ion Trap Generated by an RF Resonator

Yunjae Park, Changhyun Jung, Myeongseok Seong +3 more

A new method is proposed to measure unknown amplitudes of radio frequency (RF) voltages applied to ion traps, using a pre-calibrated voltage divider with RF shielding. In contrast to previous approaches that estimate the applied voltage by comparing the measured secular frequencies with a numerical simulation, we propose using a pre-calibrated voltage divider to determine the absolute amplitude of large RF voltages amplified by a helical resonator. The proposed method does not require measurement of secular frequencies and completely removes uncertainty caused by limitations of numerical simulations. To experimentally demonstrate our method, we first obtained a functional relation between measured secular frequencies and large amplitudes of RF voltages using the calibrated voltage divider. A comparison of measured relations and simulation results without any fitting parameters confirmed the validity of the proposed method. Our method can be applied to most ion trap experiments. In particular, it will be an essential tool for surface ion traps which are extremely vulnerable to unknown large RF voltages and for improving the accuracy of numerical simulations for ion trap experiments.

Sensors•Feb 6, 2021•4 citations

Compact field programmable gate array-based pulse-sequencer and radio-frequency generator for experiments with trapped atoms

Thaned Pruttivarasin, Hidetoshi Katori

We present a compact field-programmable gate array (FPGA) based pulse sequencer and radio-frequency (RF) generator suitable for experiments with cold trapped ions and atoms. The unit is capable of outputting a pulse sequence with at least 32 transistor-transistor logic (TTL) channels with a timing resolution of 40 ns and contains a built-in 100 MHz frequency counter for counting electrical pulses from a photo-multiplier tube. There are 16 independent direct-digital-synthesizers RF sources with fast (rise-time of ∼60 ns) amplitude switching and sub-mHz frequency tuning from 0 to 800 MHz.

arXiv:1507.03122•Review of Scientific Instruments•Nov 1, 2015•32 citations

FPGA based hardware platform for trapped-ion-based multi-level quantum systems

Ming-Dong 明东 Zhu 朱, Lin 林 Yan 闫, Xi Qin +3 more

We report a design and implementation of a field-programmable-gate-arrays (FPGA) based hardware platform, which is used to realize control and signal readout of trapped-ion-based multi-level quantum systems. This platform integrates a four-channel 2.8 Gsps@14 bits arbitrary waveform generator, a 16-channel 1 Gsps@14 bits direct-digital-synthesis-based radio-frequency generator, a 16-channel 8 ns resolution pulse generator, a 10-channel 16 bits digital-to-analog-converter module, and a 2-channel proportion integration differentiation controller. The hardware platform can be applied in the trapped-ion-based multi-level quantum systems, enabling quantum control of multi-level quantum system and high-dimensional quantum simulation. The platform is scalable and more channels for control and signal readout can be implemented by utilizing more parallel duplications of the hardware. The hardware platform also has a bright future to be applied in scaled trapped-ion-based quantum systems.

Chinese Physics B•Apr 7, 2023•5 citations

Superconducting NbTi Radiofrequency Resonator for Surface ion Traps

M. Schubert, D. Fegelein, Dominik Hanisch +3 more

Trapped-ion qubits are one approach among many for achieving scalable quantum computers. An ion trap has to be operated with several dc and radio frequency (rf) signals to trap and control its qubits. Many ion trap setups are operated at cryogenic temperatures to reduce thermal influences, to reach very high vacuum, and to achieve high fidelity for quantum operations. A resonance circuit, consisting of a coil and the capacitance of the trap electrodes, is used to step-up a low power rf signal to high amplitudes in close proximity to the ion trap. These ac fields are used to confine ions$70 \,{\rm \mu }\mathrm{m}$above a surface ion trap chip. An increased quality factor (Q-factor) of the resonance circuit leads to a higher voltage gain, but the experiment also benefits from a better attenuation of parasitic frequency components in the confining electric field. The Q-factor is inversely proportional to the trap capacitance. Since ion traps are growing in size due to a larger number of qubits, the capacitance is increasing. Therefore, the development of a coil with low losses becomes even more important. In this work, we present the setup of a superconducting coil for a high-Q resonator, measurements of the Q-factor, and its temperature dependency. The coil is made of a niobium-titanium (NbTi) wire wound on a threaded bobbin made of ceramics and equipped with further thermalization structures. The superconducting resonator is a very promising approach to satisfy the needs for future trapped-ion quantum computing setups.

IEEE Transactions on Applied Superconductivity•Jan 8, 2024•0 citations
For high-fidelity quantum operations in ion traps, it is important to maintain the secular frequency of the trapped ions at a constant value. The radial secular frequency is proportional to the amplitude of the radio frequency (RF) signal applied to ion traps. Owing to the changes in the ambient temperature of a helical resonator and the minute vibration of the optical table, the amplitude can vary. Recently, a method for reducing the fluctuation in the RF signal amplitude, using a commercial universal proportional-plus-integral (PI) controller, has been introduced, which, in turn, reduces the secular frequency drift of the trapped ions. The method improves the capability to maintain the secular frequency at a constant value. However, the structure of the controller is fixed; thus, the control method cannot be changed to suit different experimental conditions, and the different feedback configuration cannot be implemented to increase the resolution. In this paper, we develop a field-programmable gate array (FPGA)-based feedback controller that allows the implementation of various automatic control methods and feedback configurations. In our experiments, the fluctuation in the amplitude of the RF signal was 1.806% using a commercial universal PI controller. The fluctuation was reduced to 0.099% using the developed FPGA-based PI controller, and to 0.102% using the developed FPGA-based lag compensator. By employing the developed FPGA control method, many other automating control methods can be applied to achieve a stable and high-performance control of the secular frequency.
We present PyRPL, an open source software package that allows the implementation of automatic digital feedback controllers for quantum optics experiments on commercially available, affordable FPGA boards. Our software implements the digital generation of various types of error signals, from an analog input through the application of loop filters of high complexity and real-time gain adjustment for multiple analog output signals, including different algorithms for resonance search, lock acquisition sequences and in-loop gain optimization. Furthermore, all necessary diagnostic instruments such as an oscilloscope, a network analyzer and a spectrum analyzer are integrated into our software. Apart from providing a quickly scalable, automatic feedback controller, the lock performance that can be achieved by using PyRPL with imperfect equipment such as piezoelectric transducers and noisy amplifiers is better than the one achievable with standard analog controllers due to the higher complexity of implementable filters and possibilities of nonlinear operations in the FPGA. This drastically reduces the cost of added complexity when introducing additional feedback loops to an experiment. The open-source character also distinguishes PyRPL from commercial solutions, as it allows users to customize functionalities at various levels, ranging from the easy integration of PyRPL-based feedback controllers into existing setups to the modification of the FPGA functionality. A community of developers provides fast and efficient implementation and testing of software modifications.
An array of ions in a linear radio-frequency (RF) Paul trap is a good candidate for investigating structural phase transitions, such as the linear-to-zigzag (LZ) transition, due to the convenient control provided by modification of the trap confinement strength. In such studies, the trap secular frequencies are a key factor that limits the stability of the critical point (CP). In this paper, we implement secular-frequency stabilization, including active feedback stabilization of the RF voltage near the trap electrodes, and achieve a stability of better than 5~ppm over 200~s for both transverse and axial potentials. To evaluate the combined long-term stability of the trap potential in both directions, we measure the zigzag (ZZ) mode frequency near the CP, where the effect of instability in both trap directions is substantially amplified. The short-term noise within a limited spectral window is also suppressed by this scheme, as inferred from decoherence rates of the ZZ mode measured at different frequencies with Ramsey fringes. We also identify that the limitation of the secular frequency stability is mainly from the imperfect temperature insensitivity of voltage dividers and RF detectors, and as a result improvement of lab temperature stability is of great help for stabilizing the trap frequency.
A new method is proposed to measure unknown amplitudes of radio frequency (RF) voltages applied to ion traps, using a pre-calibrated voltage divider with RF shielding. In contrast to previous approaches that estimate the applied voltage by comparing the measured secular frequencies with a numerical simulation, we propose using a pre-calibrated voltage divider to determine the absolute amplitude of large RF voltages amplified by a helical resonator. The proposed method does not require measurement of secular frequencies and completely removes uncertainty caused by limitations of numerical simulations. To experimentally demonstrate our method, we first obtained a functional relation between measured secular frequencies and large amplitudes of RF voltages using the calibrated voltage divider. A comparison of measured relations and simulation results without any fitting parameters confirmed the validity of the proposed method. Our method can be applied to most ion trap experiments. In particular, it will be an essential tool for surface ion traps which are extremely vulnerable to unknown large RF voltages and for improving the accuracy of numerical simulations for ion trap experiments.
We present a compact field-programmable gate array (FPGA) based pulse sequencer and radio-frequency (RF) generator suitable for experiments with cold trapped ions and atoms. The unit is capable of outputting a pulse sequence with at least 32 transistor-transistor logic (TTL) channels with a timing resolution of 40 ns and contains a built-in 100 MHz frequency counter for counting electrical pulses from a photo-multiplier tube. There are 16 independent direct-digital-synthesizers RF sources with fast (rise-time of ∼60 ns) amplitude switching and sub-mHz frequency tuning from 0 to 800 MHz.
We report a design and implementation of a field-programmable-gate-arrays (FPGA) based hardware platform, which is used to realize control and signal readout of trapped-ion-based multi-level quantum systems. This platform integrates a four-channel 2.8 Gsps@14 bits arbitrary waveform generator, a 16-channel 1 Gsps@14 bits direct-digital-synthesis-based radio-frequency generator, a 16-channel 8 ns resolution pulse generator, a 10-channel 16 bits digital-to-analog-converter module, and a 2-channel proportion integration differentiation controller. The hardware platform can be applied in the trapped-ion-based multi-level quantum systems, enabling quantum control of multi-level quantum system and high-dimensional quantum simulation. The platform is scalable and more channels for control and signal readout can be implemented by utilizing more parallel duplications of the hardware. The hardware platform also has a bright future to be applied in scaled trapped-ion-based quantum systems.
Trapped-ion qubits are one approach among many for achieving scalable quantum computers. An ion trap has to be operated with several dc and radio frequency (rf) signals to trap and control its qubits. Many ion trap setups are operated at cryogenic temperatures to reduce thermal influences, to reach very high vacuum, and to achieve high fidelity for quantum operations. A resonance circuit, consisting of a coil and the capacitance of the trap electrodes, is used to step-up a low power rf signal to high amplitudes in close proximity to the ion trap. These ac fields are used to confine ions70 μm70 \,{\rm \mu }\mathrm{m}70μmabove a surface ion trap chip. An increased quality factor (Q-factor) of the resonance circuit leads to a higher voltage gain, but the experiment also benefits from a better attenuation of parasitic frequency components in the confining electric field. The Q-factor is inversely proportional to the trap capacitance. Since ion traps are growing in size due to a larger number of qubits, the capacitance is increasing. Therefore, the development of a coil with low losses becomes even more important. In this work, we present the setup of a superconducting coil for a high-Q resonator, measurements of the Q-factor, and its temperature dependency. The coil is made of a niobium-titanium (NbTi) wire wound on a threaded bobbin made of ceramics and equipped with further thermalization structures. The superconducting resonator is a very promising approach to satisfy the needs for future trapped-ion quantum computing setups.