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

arXiv:2610.35227

A Control Line Multiplexing Framework for Scalable Quantum Computing

Dayu Li, Naibin Zhou, Zhiyuan Chen, Zihua Chen, Yu Xu, Yuan Li, Daojin Fan, Wenhao Chu, Xiawei Chen, Hui Deng, Jiacheng Gui, Linyin Hong, Bo Fan, Weiping Lin, Haonan Zou, Haoxin Lou, Xintao Zhao, Sirui Cao, Ying Chong, Qingling Zhu, Chen Wang, Yisen Hu, Kaili Zhang, Feifan Su, Haibin Zhang, Jianghan Yin, Yajie Du, Yinan Jiang, Haoping Luo, Weifeng Yang, Jiafei Wang, Jin Lin, Futian Liang, Hao Rong, Kai Yan, Ming Gong, Jinjin Li, Maliang Liu, Cheng-Zhi Peng, Shaowei Li, Xiaobo Zhu, Jian-Wei Pan

quant-phSubmitted Oct 26, 2026• Announced Oct 27, 2026• 0 citations• Revised Oct 28, 2026 (v3)
v1 · Oct 26, 2026v2 · Oct 27, 2026v3 · Oct 28, 2026
arXivHTMLPDF

Abstract

Universal fault-tolerant superconducting quantum computers are expected to require millions of physical qubits; yet extending the prevailing dedicated-control-line paradigm to this scale would exceed the wiring density and cooling-power budget of dilution refrigerators. Microwave frequency-division multiplexing (FDM) revolutionized classical communications by enabling many independent channels to share common transmission infrastructure. Translating this principle to superconducting quantum control, however, requires an all-microwave architecture and experimental validation of frequency-multiplexed gate control. Recent work in quantum error correction has demonstrated microwave-based readout, single-qubit gates and leakage suppression, whereas two-qubit gates remain predominantly driven by unipolar pulses and thus constitute the missing element of an all-microwave architecture. Here, we propose a periodically extensible hybrid multiplexing framework in which all gate operations are frequency-division multiplexed using polychromatic microwave pulses and band-pass filters, thereby reducing the required control-line count by one to two orders of magnitude. In a 1:4 demonstration, we achieve average errors of $(6.4\pm0.2)\times10^{-3}$ for parallel FDM CZ gates and $(10.6\pm0.2)\times10^{-4}$ for parallel FDM $XY(π/2)$ gates, without statistically significant multiplexing-induced degradation. Together with on-chip DC sources, this FDM-based gate-control scheme completes the last missing module in a scalable multiplexed-control architecture toward universal fault-tolerant quantum computing.

AI Summary

The paper addresses control-line overhead in superconducting processors by combining frequency-division multiplexing (FDM) of microwave-driven single- and two-qubit gates with time-division multiplexing (TDM) and on-chip DC bias sources. Multitone waveforms are routed through band-pass filters; parametrically driven coupler CZ gates supply the frequency-addressable entangling operation. A four-channel experiment demonstrates simultaneous $XY(\pi/2)$ gates and, separately, four simultaneous CZ gates through shared waveform-generation channels. Average XEB-derived errors are $(10.57\pm0.23)\times10^{-4}$ for single-qubit gates and $(6.43\pm0.16)\times10^{-3}$ for CZ gates, versus dedicated-channel baselines of $(10.38\pm0.35)\times10^{-4}$ and $(6.53\pm0.24)\times10^{-3}$. Gates last 40 ns and 120 ns, respectively, with an additional 8 ns idle interval for CZ. Comparisons across dedicated, filtered, predistorted and multiplexed configurations find no statistically significant multiplexing-induced increase after filter-response compensation. Hamiltonian analysis and simulations identify harmonic swap, leakage and coupler-excitation resonances constraining frequency allocation. Periodic frequency plans project 12-fold control-line reduction using experimental gate parameters and 48-fold reduction under idealized assumptions. At 381,000 qubits, the latter yields an estimated passive cable load of $8.33\,\mu\mathrm{W}$, versus $400.05\,\mu\mathrm{W}$ without multiplexing. Filters and splitting are implemented at room temperature, so cryogenic wiring reduction is not demonstrated. The 48-fold projection assumes longer gates, sufficiently long coherence, idealized filtering and nominal frequency assignments; its crosstalk analysis is not a complete multitone error budget. Thermal estimates exclude filters, switches, splitters, packaging and bias-source loads. Cryogenic integration and robustness to device variability remain unresolved.

Little sign of AI-generated textOverclaimsStrong assumptions

Written by gpt-6.1-sol from the paper's full text. Automated: it can be wrong.

Comments
22 pages, 4 figures, 1 table; includes 11 pages of supplementary material with 14 figures and 2 tables

Related papers

Orthogonal frequency-division multiplexing for simultaneous gate operations on multiple qubits via a shared control line

Haruki Mitarai, Yukihiro Tadokoro, Hiroya Tanaka

The increasing number of qubits in quantum processors necessitates a corresponding increase in the number of control lines between the processor, which is typically operated at cryogenic temperatures, and external electronics. Scaling poses significant challenges in terms of the thermal loads, forming a major bottleneck in the realization of large-scale quantum computers. In this study, we analyze simultaneous gate operations on multiple qubits using microwaves transmitted via a single cable in a frequency-division multiplexing (FDM) scheme. By employing rectangular control microwave pulses, we reveal the contribution of drive frequency spacing to gate fidelity. Through theoretical and numerical analyses, we demonstrate that orthogonal and quasi-orthogonal microwave signals suppress interference in simultaneously driven qubits, thereby ensuring high gate fidelity. Additionally, we provide design guidelines for key parameters, including pulse length, number of multiplexed microwave signals, and rotation angle, to achieve precise qubit operations. Our findings enable a scalable FDM-based microwave control scheme suitable for quantum processors with a large number of qubits.

quant-pharXiv:2511.16855•Physical Review Applied•Nov 24, 2025•1 citation

A multiplexed control architecture for superconducting qubits with row-column addressing

Zhao, Peng

In state-of-the-art superconducting quantum processors, each qubit is controlled by at least one control line that delivers control pulses generated at room temperature to qubits operating at millikelvin temperatures. While this strategy has been successfully applied to control hundreds of qubits, it is unlikely to be scalable to control thousands of qubits, let alone millions or even billions of qubits needed in fault-tolerance quantum computing. The primary obstacle lies in the wiring challenge, wherein the number of accommodated control lines is limited by factors, such as the cooling power, physical space of the cryogenic system, the control footprint area at the qubit chip level, and so on. Here, we introduce a multiplexed control architecture for superconducting qubits with two types of shared control lines, row and column lines, providing an efficient approach for parallel controlling $N$ qubits with $O(\sqrt{N})$ control lines. With the combination of the two-type shared lines, unique pairs of control pulses are delivered to qubits at each row-column intersection, enabling parallel qubit addressing. Of particular concern here is that, unlike traditional gate schemes, both single- and two-qubit gates are implemented with pairs of control pulses. Considering the inherent parallelism and the control limitations, the integration of the architecture into quantum computing systems should be tailored as much as possible to the specific properties of the quantum circuits to be executed. As such, the architecture could be scalable for executing structured quantum circuits, such as quantum error correction circuits.

arXiv:2403.03717•Mar 6, 2024•1 citation

Multiplexed double-transmon coupler scheme in scalable superconducting quantum processor

Tianqi Cai, Chitong Chen, Kunliang Bu +7 more

Precise control of superconducting qubits is essential for advancing both quantum simulation and quantum error correction. Recently, transmon qubit systems employing the single-transmon coupler (STC) scheme have demonstrated high-fidelity single- and two-qubit gate operations by dynamically tuning the effective coupling between qubits. However, the integration of STCs increases the number of control lines, thereby posing a significant bottleneck for chip routing and scalability. To address this challenge, we propose a robust control line multiplexing scheme based on a double-transmon coupler (DTC) architecture, which enables shared coupler control lines to substantially reduce wiring complexity. Moreover, we experimentally verify that this multiplexed configuration efficiently suppresses undesirable static $ZZ$ coupling while maintaining accurate control over two-qubit gate operations. We further demonstrate the feasibility of the architecture through two distinct gate implementations: a fast coupler $Z$-control-based CZ gate and a parametric iSWAP gate. To validate the practical applicability of this multiplexing approach in quantum circuits, we prepare Bell and three-qubit GHZ states using the proposed scheme with fidelity exceeding 99% and 96%, respectively. This multiplexed DTC architecture offers significant potential to minimize wiring overhead in two-dimensional qubit arrays, thereby greatly enhancing the scalability of superconducting quantum processors.

quant-pharXiv:2511.02249•Nov 5, 2025•0 citations

A Cryo-CMOS Controller IC With Fully Integrated Frequency Generators for Superconducting Qubits

Kiseo Kang, Donggyu Minn, Seunghun Bae +7 more

Extensive research on quantum mechanics in past decades has successfully paved the way towards the disruptive technology of quantum computing. A further step to the realization of a fault-tolerant scalable quantum computer is presenting challenges in the field of engineering. It necessitates a microsystem operating at 4K in a dilution refrigerator, which would be inevitable to control thousands or millions of qubits sitting at 10mK. There have been IC implementations of pulse modulators generating qubit-controlling microwave signals [1– 4]. The pulse modulation based on direct synthesis demonstrated feasibility of driving multiple qubits with frequency-division multiplexing (FDM) through one RF cable [1 – 3]. The first implementation of a full controller [1], which includes both read and write chains for spin qubits, demonstrated the highest level of integration. However, the previous work used external local oscillator (LO) sources for frequency synthesis. External feeding of LO requires precise matching; otherwise, a failure would cause leakage to the qubit driving output through PCB traces, resulting in AC-Stark shift of qubit state by unwanted tones at near-resonance. It becomes more problematic in FDM-based multi-qubit driving. Since the fidelity of qubit operations strongly relies on the quality of driving frequency, a low-noise LO generation by a phase-locked loop (PLL) is one of the most important factors [5]. The internal generation of LO gives additional benefits in superconducting qubit interface. It necessitates multiple LOs since the superconducting qubit uses microwave pulse driving for both read and write. To detect the state of a qubit through dispersive readout, the phase reflected from the readout resonator should be measured. Therefore, the driving pulses for the read and the write should be synchronized to a single reference timing. Using built-in PLLs sharing a single reference clock naturally solves this problem.

Digest of technical papers/Digest of technical papers - IEEE International Solid-State Circuits Conference•Feb 20, 2022•45 citations

All-optical control and multiplexed readout of multiple superconducting qubits

Xiaoxuan Pan, Chuanlong Ma, Jia-Qi Wang +12 more

Superconducting quantum circuits operate at millikelvin temperatures, typically requiring independent microwave cables for each qubit for connecting room-temperature control and readout electronics. However, scaling to large-scale processors hosting hundreds of qubits faces a severe input/output (I/O) bottleneck, as the dense cable arrays impose prohibitive constraints on physical footprint, thermal load, wiring complexity, and cost. Here we demonstrate a complete optical I/O architecture for superconducting quantum circuits, in which all control and readout signals are transmitted exclusively via optical photons. Employing a broadband traveling-wave Brillouin microwave-to-optical transducer, we achieve simultaneous frequency-multiplexed optical readout of two qubits. Combined with fiber-integrated photodiode arrays for control signal delivery, this closed-loop optical I/O introduces no measurable degradation to qubit coherence times, with an optically driven single-qubit gate fidelity showing only a 0.19% reduction relative to standard microwave operation. These results establish optical interconnects as a viable path toward large-scale superconducting quantum processors, and open the possibility of networking multiple superconducting quantum computers housed in separate dilution refrigerators through a centralized room-temperature control infrastructure.

quant-pharXiv:2512.21199•Dec 25, 2025•0 citations

Multiplexed control scheme for scalable quantum information processing with superconducting qubits

Shi, Pan, Jiahao Yuan, Fei Yan +1 more

The advancement of scalable quantum information processing relies on the accurate and parallel manipulation of a vast number of qubits, potentially reaching into the millions. Superconducting qubits, traditionally controlled through individual circuitry, currently face a formidable scalability challenge due to the excessive use of wires. This challenge is nearing a critical point where it might soon surpass the capacities of on-chip routing, I/O packaging, testing platforms, and economically feasible solutions. Here we introduce a multiplexed control scheme that efficiently utilizes shared control lines for operating multiple qubits and couplers. By integrating quantum hardware-software co-design, our approach utilizes advanced techniques like frequency multiplexing and individual tuning. This enables simultaneous and independent execution of single- and two-qubit gates with significantly simplified wiring. This scheme has the potential to diminish the number of control lines by one to two orders of magnitude in the near future, thereby substantially enhancing the scalability of superconducting quantum processors.

arXiv:2312.06911•Dec 12, 2023•3 citations
Universal fault-tolerant superconducting quantum computers are expected to require millions of physical qubits; yet extending the prevailing dedicated-control-line paradigm to this scale would exceed the wiring density and cooling-power budget of dilution refrigerators. Microwave frequency-division multiplexing (FDM) revolutionized classical communications by enabling many independent channels to share common transmission infrastructure. Translating this principle to superconducting quantum control, however, requires an all-microwave architecture and experimental validation of frequency-multiplexed gate control. Recent work in quantum error correction has demonstrated microwave-based readout, single-qubit gates and leakage suppression, whereas two-qubit gates remain predominantly driven by unipolar pulses and thus constitute the missing element of an all-microwave architecture. Here, we propose a periodically extensible hybrid multiplexing framework in which all gate operations are frequency-division multiplexed using polychromatic microwave pulses and band-pass filters, thereby reducing the required control-line count by one to two orders of magnitude. In a 1:4 demonstration, we achieve average errors of (6.4±0.2)×10−3(6.4\pm0.2)\times10^{-3}(6.4±0.2)×10−3 for parallel FDM CZ gates and (10.6±0.2)×10−4(10.6\pm0.2)\times10^{-4}(10.6±0.2)×10−4 for parallel FDM XY(π/2)XY(π/2)XY(π/2) gates, without statistically significant multiplexing-induced degradation. Together with on-chip DC sources, this FDM-based gate-control scheme completes the last missing module in a scalable multiplexed-control architecture toward universal fault-tolerant quantum computing.
The paper addresses control-line overhead in superconducting processors by combining frequency-division multiplexing (FDM) of microwave-driven single- and two-qubit gates with time-division multiplexing (TDM) and on-chip DC bias sources. Multitone waveforms are routed through band-pass filters; parametrically driven coupler CZ gates supply the frequency-addressable entangling operation.
A four-channel experiment demonstrates simultaneous XY(π/2)XY(\pi/2)XY(π/2) gates and, separately, four simultaneous CZ gates through shared waveform-generation channels. Average XEB-derived errors are (10.57±0.23)×10−4(10.57\pm0.23)\times10^{-4}(10.57±0.23)×10−4 for single-qubit gates and (6.43±0.16)×10−3(6.43\pm0.16)\times10^{-3}(6.43±0.16)×10−3 for CZ gates, versus dedicated-channel baselines of (10.38±0.35)×10−4(10.38\pm0.35)\times10^{-4}(10.38±0.35)×10−4 and (6.53±0.24)×10−3(6.53\pm0.24)\times10^{-3}(6.53±0.24)×10−3. Gates last 40 ns and 120 ns, respectively, with an additional 8 ns idle interval for CZ. Comparisons across dedicated, filtered, predistorted and multiplexed configurations find no statistically significant multiplexing-induced increase after filter-response compensation. Hamiltonian analysis and simulations identify harmonic swap, leakage and coupler-excitation resonances constraining frequency allocation.
Periodic frequency plans project 12-fold control-line reduction using experimental gate parameters and 48-fold reduction under idealized assumptions. At 381,000 qubits, the latter yields an estimated passive cable load of 8.33 μW8.33\,\mu\mathrm{W}8.33μW, versus 400.05 μW400.05\,\mu\mathrm{W}400.05μW without multiplexing.
Filters and splitting are implemented at room temperature, so cryogenic wiring reduction is not demonstrated. The 48-fold projection assumes longer gates, sufficiently long coherence, idealized filtering and nominal frequency assignments; its crosstalk analysis is not a complete multitone error budget. Thermal estimates exclude filters, switches, splitters, packaging and bias-source loads. Cryogenic integration and robustness to device variability remain unresolved.
The increasing number of qubits in quantum processors necessitates a corresponding increase in the number of control lines between the processor, which is typically operated at cryogenic temperatures, and external electronics. Scaling poses significant challenges in terms of the thermal loads, forming a major bottleneck in the realization of large-scale quantum computers. In this study, we analyze simultaneous gate operations on multiple qubits using microwaves transmitted via a single cable in a frequency-division multiplexing (FDM) scheme. By employing rectangular control microwave pulses, we reveal the contribution of drive frequency spacing to gate fidelity. Through theoretical and numerical analyses, we demonstrate that orthogonal and quasi-orthogonal microwave signals suppress interference in simultaneously driven qubits, thereby ensuring high gate fidelity. Additionally, we provide design guidelines for key parameters, including pulse length, number of multiplexed microwave signals, and rotation angle, to achieve precise qubit operations. Our findings enable a scalable FDM-based microwave control scheme suitable for quantum processors with a large number of qubits.
In state-of-the-art superconducting quantum processors, each qubit is controlled by at least one control line that delivers control pulses generated at room temperature to qubits operating at millikelvin temperatures. While this strategy has been successfully applied to control hundreds of qubits, it is unlikely to be scalable to control thousands of qubits, let alone millions or even billions of qubits needed in fault-tolerance quantum computing. The primary obstacle lies in the wiring challenge, wherein the number of accommodated control lines is limited by factors, such as the cooling power, physical space of the cryogenic system, the control footprint area at the qubit chip level, and so on. Here, we introduce a multiplexed control architecture for superconducting qubits with two types of shared control lines, row and column lines, providing an efficient approach for parallel controlling NNN qubits with O(N)O(\sqrt{N})O(N​) control lines. With the combination of the two-type shared lines, unique pairs of control pulses are delivered to qubits at each row-column intersection, enabling parallel qubit addressing. Of particular concern here is that, unlike traditional gate schemes, both single- and two-qubit gates are implemented with pairs of control pulses. Considering the inherent parallelism and the control limitations, the integration of the architecture into quantum computing systems should be tailored as much as possible to the specific properties of the quantum circuits to be executed. As such, the architecture could be scalable for executing structured quantum circuits, such as quantum error correction circuits.
Precise control of superconducting qubits is essential for advancing both quantum simulation and quantum error correction. Recently, transmon qubit systems employing the single-transmon coupler (STC) scheme have demonstrated high-fidelity single- and two-qubit gate operations by dynamically tuning the effective coupling between qubits. However, the integration of STCs increases the number of control lines, thereby posing a significant bottleneck for chip routing and scalability. To address this challenge, we propose a robust control line multiplexing scheme based on a double-transmon coupler (DTC) architecture, which enables shared coupler control lines to substantially reduce wiring complexity. Moreover, we experimentally verify that this multiplexed configuration efficiently suppresses undesirable static ZZZZZZ coupling while maintaining accurate control over two-qubit gate operations. We further demonstrate the feasibility of the architecture through two distinct gate implementations: a fast coupler ZZZ-control-based CZ gate and a parametric iSWAP gate. To validate the practical applicability of this multiplexing approach in quantum circuits, we prepare Bell and three-qubit GHZ states using the proposed scheme with fidelity exceeding 99% and 96%, respectively. This multiplexed DTC architecture offers significant potential to minimize wiring overhead in two-dimensional qubit arrays, thereby greatly enhancing the scalability of superconducting quantum processors.
Extensive research on quantum mechanics in past decades has successfully paved the way towards the disruptive technology of quantum computing. A further step to the realization of a fault-tolerant scalable quantum computer is presenting challenges in the field of engineering. It necessitates a microsystem operating at 4K in a dilution refrigerator, which would be inevitable to control thousands or millions of qubits sitting at 10mK. There have been IC implementations of pulse modulators generating qubit-controlling microwave signals [1– 4]. The pulse modulation based on direct synthesis demonstrated feasibility of driving multiple qubits with frequency-division multiplexing (FDM) through one RF cable [1 – 3]. The first implementation of a full controller [1], which includes both read and write chains for spin qubits, demonstrated the highest level of integration. However, the previous work used external local oscillator (LO) sources for frequency synthesis. External feeding of LO requires precise matching; otherwise, a failure would cause leakage to the qubit driving output through PCB traces, resulting in AC-Stark shift of qubit state by unwanted tones at near-resonance. It becomes more problematic in FDM-based multi-qubit driving. Since the fidelity of qubit operations strongly relies on the quality of driving frequency, a low-noise LO generation by a phase-locked loop (PLL) is one of the most important factors [5]. The internal generation of LO gives additional benefits in superconducting qubit interface. It necessitates multiple LOs since the superconducting qubit uses microwave pulse driving for both read and write. To detect the state of a qubit through dispersive readout, the phase reflected from the readout resonator should be measured. Therefore, the driving pulses for the read and the write should be synchronized to a single reference timing. Using built-in PLLs sharing a single reference clock naturally solves this problem.
Superconducting quantum circuits operate at millikelvin temperatures, typically requiring independent microwave cables for each qubit for connecting room-temperature control and readout electronics. However, scaling to large-scale processors hosting hundreds of qubits faces a severe input/output (I/O) bottleneck, as the dense cable arrays impose prohibitive constraints on physical footprint, thermal load, wiring complexity, and cost. Here we demonstrate a complete optical I/O architecture for superconducting quantum circuits, in which all control and readout signals are transmitted exclusively via optical photons. Employing a broadband traveling-wave Brillouin microwave-to-optical transducer, we achieve simultaneous frequency-multiplexed optical readout of two qubits. Combined with fiber-integrated photodiode arrays for control signal delivery, this closed-loop optical I/O introduces no measurable degradation to qubit coherence times, with an optically driven single-qubit gate fidelity showing only a 0.19% reduction relative to standard microwave operation. These results establish optical interconnects as a viable path toward large-scale superconducting quantum processors, and open the possibility of networking multiple superconducting quantum computers housed in separate dilution refrigerators through a centralized room-temperature control infrastructure.
The advancement of scalable quantum information processing relies on the accurate and parallel manipulation of a vast number of qubits, potentially reaching into the millions. Superconducting qubits, traditionally controlled through individual circuitry, currently face a formidable scalability challenge due to the excessive use of wires. This challenge is nearing a critical point where it might soon surpass the capacities of on-chip routing, I/O packaging, testing platforms, and economically feasible solutions. Here we introduce a multiplexed control scheme that efficiently utilizes shared control lines for operating multiple qubits and couplers. By integrating quantum hardware-software co-design, our approach utilizes advanced techniques like frequency multiplexing and individual tuning. This enables simultaneous and independent execution of single- and two-qubit gates with significantly simplified wiring. This scheme has the potential to diminish the number of control lines by one to two orders of magnitude in the near future, thereby substantially enhancing the scalability of superconducting quantum processors.