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

Nature Communications

Dispersive detection of a charge qubit with a broadband high-impedance quantum-Hall plasmon resonator

Chaojing Lin, Kosei Teshima, Takafumi Akiho, Koji Muraki, T. Fujisawa

Published Feb 10, 2026• 0 citations
Publisher

Abstract

Cavity quantum electrodynamics (cQED) provides strong light-matter interactions that can be used for manipulating and detecting quantum states. The interaction can be enhanced by increasing the resonator’s impedance, while approaching the quantum impedance (h/e2) remains challenging. Edge plasmons emergent as chiral bosonic modes in the quantum Hall channels provide high quantized impedance of h/νe2 that can exceed 10 kΩ for the Landau-level filling factor ν $$\le$$ 2, well beyond the impedance of free space. Here, we apply such a high-impedance plasmon mode in a quantum-Hall plasmon resonator to demonstrate dispersive detection of a nearby charge qubit formed in a double quantum dot. The phase shift in microwave transmission through the plasmon resonator follows the dispersive shift associated with the qubit state, in agreement with the cQED theory. The high impedance allows us to perform dispersive detection of qubit spectroscopy with a plasmon resonator having a broad bandwidth. Leveraging these topological edge modes, our results establish two-dimensional topological insulators as a new platform of cQED. Recent work reported plasmon-assisted tunneling in a double quantum dot coupled to a plasmon mode in a quantum Hall plasmon resonator. Here, the authors leverage this system to achieve broadband dispersive readout of a semiconductor charge qubit formed by a double quantum dot.

DOI
10.1038/s41467-026-69342-y

Related papers

Dispersive detection of a charge qubit with a broadband high-impedance quantum-Hall plasmon resonator

Chaojing Lin, Kosei Teshima, Takafumi Akiho +2 more

Cavity quantum electrodynamics (cQED) provides strong light-matter interactions that can be used for manipulating and detecting quantum states. The interaction can be enhanced by increasing the resonator's impedance, while approaching the quantum impedance ($h/e^2$) remains challenging. Edge plasmons emergent as chiral bosonic modes in the quantum Hall channels provide high quantized impedance of $h/ νe^2$ that can exceed 10 k$Ω$ for the Landau-level filling factor $ν\leq 2$, well beyond the impedance of free space. Here, we apply such a high-impedance plasmon mode in a quantum-Hall plasmon resonator to demonstrate dispersive detection of a nearby charge qubit formed in a double quantum dot. The phase shift in microwave transmission through the plasmon resonator follows the dispersive shift associated with the qubit state in agreement with the cQED theory. The high impedance allows us to perform dispersive detection of qubit spectroscopy with a plasmon resonator having a broad bandwidth. Leveraging these topological edge modes, our results establish two-dimensional topological insulators as a new platform of cQED.

arXiv:2602.10472•Feb 11, 2026•0 citations

Electric Dipole Coupling of a Bilayer Graphene Quantum Dot to a High-Impedance Microwave Resonator

Max Josef Ruckriegel, Lisa Maria Gächter, David Kealhofer +12 more

High Resolution Image Download MS PowerPoint Slide We implement circuit quantum electrodynamics (cQED) with quantum dots in bilayer graphene, a maturing material platform that can host long-lived spin and valley states. Our device combines a high-impedance ( Z r ≈ 1 kΩ) superconducting microwave resonator with a double quantum dot electrostatically defined in a graphene-based van der Waals heterostructure. Electric dipole coupling between the subsystems allows the resonator to sense the electric susceptibility of the double quantum dot from which we reconstruct its charge stability diagram. We achieve sensitive and fast detection of the interdot transition with a signal-to-noise ratio of 3.5 within 1 μs integration time. The charge–photon interaction is quantified in the dispersive and resonant regimes by comparing the resonator response to input–output theory, yielding a coupling strength of g /2π = 49.7 MHz. Our results introduce cQED as a probe for quantum dots in van der Waals materials and indicate a path toward coherent charge–photon coupling with bilayer graphene quantum dots.

arXiv:2312.14629•Nano Letters•Jun 4, 2024•8 citations

All-Microwave Control and Dispersive Readout of Gate-Defined Quantum Dot Qubits in Circuit Quantum Electrodynamics

Pasquale Scarlino, David J. van Woerkom, Anna Stockklauser +8 more

Developing fast and accurate control and readout techniques is an important challenge in quantum information processing with semiconductor qubits. Here, we study the dynamics and the coherence properties of a GaAs/AlGaAs double quantum dot charge qubit strongly coupled to a frequency-tunable high-impedance resonator. We drive qubit transitions with synthesized microwave pulses and perform qubit readout through the state-dependent frequency shift imparted by the qubit on the dispersively coupled resonator. We perform Rabi oscillation, Ramsey fringe, energy relaxation, and Hahn-echo measurements and find significantly reduced decoherence rates down to γ_{2}/2π∼3 MHz corresponding to coherence times of up to T_{2}∼50 ns for charge states in gate-defined quantum dot qubits. We realize Rabi π pulses of width down to σ∼0.25 ns.

arXiv:1711.01906•Physical Review Letters•May 22, 2019•67 citations

Strong Charge-Photon Coupling and High-Efficiency Microwave Photodetection in Hybrid Quantum Dot-Resonator Systems

Oppliger, Fabian

This thesis investigates hybrid circuit quantum electrodynamics (cQED) as a versatile platform that unites superconducting resonators with semiconductor quantum dots. The central motivation is to harness strong light-matter coupling at the single-photon level, which enables coherent photon-qubit interactions and paves the way for quantum technologies in computation, communication, and sensing. The first part of this work combines hybrid cQED with holes in planar Ge/SiGe, a material system that has only recently become accessible for quantum devices. Planar Ge offers unique advantages for this purpose and has attracted considerable attention in the context of quantum computing. In contrast, its potential for hybrid cQED has remained largely unexplored, making the present work one of the first demonstrations of strong light-matter interaction in this platform. Within this framework, we demonstrate strong charge-photon coupling in planar Ge by observing vacuum Rabi splitting between a hole charge qubit based on a double quantum dot (DQD) and a microwave resonator. We employ a frequency-tunable high-impedance resonator to perform qubit spectroscopy, enabling systematic exploration of coupling regimes and confirming device controllability. In addition, we use this setup to carry out excited-state spectroscopy of strongly correlated states in the DQD, revealing the formation of Wigner molecules and illustrating how the hybrid architecture can be harnessed to access many-body physics. While these experiments in Ge demonstrate how strong coupling can be harnessed to explore qubit physics and correlated states, they also exemplify the wider potential of hybrid cQED. A particularly pressing application is in quantum optics, where efficient single-photon detectors are still lacking in the microwave regime. Such detectors are essential for enabling experiments in quantum communication and microwave quantum optics. In the second part of this thesis, we address this challenge by realizing a photodetector based on a GaAs DQD coupled to a superconducting resonator. The detector operates via photon-to-charge conversion and achieves efficiencies approaching unity. Strong coupling plays a central role by ensuring that incoming photons are absorbed before being lost to the environment, which is key to the high performance of the detector. We further exploit the frequency tunability of the resonator to investigate device performance and identify the parameters that optimize detection efficiency. The broader impact of this work lies in advancing quantum technologies that rely on coherent microwave photons. Applications include spin qubit readout, long-distance photon-mediated coupling, quantum communication, and microwave quantum optics. Looking forward, planar Ge is identified as a highly competitive platform for hybrid cQED. Future directions include the development of single-photon sources, quantum- limited detectors, and analog quantum simulators based on engineered resonator-qubit arrays.

•Jan 1, 2025•0 citations

Tunable high-efficiency microwave photon detector based on a double quantum dot coupled to a superconducting high-impedance cavity

Fabian Oppliger, Wonjin Jang, Aldo Tarascio +6 more

High-efficiency single-photon detection in the microwave domain is a key enabling technology for various quantum applications. However, the extremely low energy of microwave photons presents a fundamental challenge, preventing direct photon-to-charge conversion as achieved in optical systems using semiconductors. Here, we demonstrate continuous microwave photon detection with an efficiency approaching 70% in the single-photon regime. We use a hybrid system comprising a gate-defined double quantum dot (DQD) charge qubit in a gallium arsenide/aluminum gallium arsenide heterostructure, coupled to a high-impedance Josephson junction array cavity. We systematically optimize the hybrid architecture to maximize the detection efficiency by leveraging strong charge-photon coupling, tunable DQD tunnel rates, and the frequency tunability of both subsystems. The system efficiency is characterized over a frequency range of 3 to 5.2 gigahertz. Our results establish semiconductor-based cavity-quantum electrodynamics architectures as a scalable and versatile platform for efficient microwave photon detection, opening promising avenues for quantum microwave optics and quantum information technologies.

arXiv:2506.19828•Science Advances•Apr 3, 2026•4 citations

Tunable high-efficiency microwave photon detector based on a double quantum dot coupled to a superconducting high-impedance cavity

Fabian Oppliger, Wonjin Jang, Aldo Tarascio +6 more

High-efficiency single-photon detection in the microwave domain is a key enabling technology for various quantum applications. However, the extremely low energy of microwave photons presents a fundamental challenge, preventing direct photon-to-charge conversion as achieved in optical systems using semiconductors. Here, we demonstrate continuous microwave photon detection with an efficiency approaching 70% in the single-photon regime. We use a hybrid system comprising a gate-defined double quantum dot (DQD) charge qubit in a gallium arsenide/aluminum gallium arsenide heterostructure, coupled to a high-impedance Josephson junction array cavity. We systematically optimize the hybrid architecture to maximize the detection efficiency by leveraging strong charge-photon coupling, tunable DQD tunnel rates, and the frequency tunability of both subsystems. The system efficiency is characterized over a frequency range of 3 to 5.2 gigahertz. Our results establish semiconductor-based cavity-quantum electrodynamics architectures as a scalable and versatile platform for efficient microwave photon detection, opening promising avenues for quantum microwave optics and quantum information technologies.

•Apr 1, 2026•0 citations
Cavity quantum electrodynamics (cQED) provides strong light-matter interactions that can be used for manipulating and detecting quantum states. The interaction can be enhanced by increasing the resonator’s impedance, while approaching the quantum impedance (h/e2) remains challenging. Edge plasmons emergent as chiral bosonic modes in the quantum Hall channels provide high quantized impedance of h/νe2 that can exceed 10 kΩ for the Landau-level filling factor ν ≤\le≤ 2, well beyond the impedance of free space. Here, we apply such a high-impedance plasmon mode in a quantum-Hall plasmon resonator to demonstrate dispersive detection of a nearby charge qubit formed in a double quantum dot. The phase shift in microwave transmission through the plasmon resonator follows the dispersive shift associated with the qubit state, in agreement with the cQED theory. The high impedance allows us to perform dispersive detection of qubit spectroscopy with a plasmon resonator having a broad bandwidth. Leveraging these topological edge modes, our results establish two-dimensional topological insulators as a new platform of cQED. Recent work reported plasmon-assisted tunneling in a double quantum dot coupled to a plasmon mode in a quantum Hall plasmon resonator. Here, the authors leverage this system to achieve broadband dispersive readout of a semiconductor charge qubit formed by a double quantum dot.
Cavity quantum electrodynamics (cQED) provides strong light-matter interactions that can be used for manipulating and detecting quantum states. The interaction can be enhanced by increasing the resonator's impedance, while approaching the quantum impedance (h/e2h/e^2h/e2) remains challenging. Edge plasmons emergent as chiral bosonic modes in the quantum Hall channels provide high quantized impedance of h/νe2h/ νe^2h/νe2 that can exceed 10 kΩΩΩ for the Landau-level filling factor ν≤2ν\leq 2ν≤2, well beyond the impedance of free space. Here, we apply such a high-impedance plasmon mode in a quantum-Hall plasmon resonator to demonstrate dispersive detection of a nearby charge qubit formed in a double quantum dot. The phase shift in microwave transmission through the plasmon resonator follows the dispersive shift associated with the qubit state in agreement with the cQED theory. The high impedance allows us to perform dispersive detection of qubit spectroscopy with a plasmon resonator having a broad bandwidth. Leveraging these topological edge modes, our results establish two-dimensional topological insulators as a new platform of cQED.
High Resolution Image Download MS PowerPoint Slide We implement circuit quantum electrodynamics (cQED) with quantum dots in bilayer graphene, a maturing material platform that can host long-lived spin and valley states. Our device combines a high-impedance ( Z r ≈ 1 kΩ) superconducting microwave resonator with a double quantum dot electrostatically defined in a graphene-based van der Waals heterostructure. Electric dipole coupling between the subsystems allows the resonator to sense the electric susceptibility of the double quantum dot from which we reconstruct its charge stability diagram. We achieve sensitive and fast detection of the interdot transition with a signal-to-noise ratio of 3.5 within 1 μs integration time. The charge–photon interaction is quantified in the dispersive and resonant regimes by comparing the resonator response to input–output theory, yielding a coupling strength of g /2π = 49.7 MHz. Our results introduce cQED as a probe for quantum dots in van der Waals materials and indicate a path toward coherent charge–photon coupling with bilayer graphene quantum dots.
Developing fast and accurate control and readout techniques is an important challenge in quantum information processing with semiconductor qubits. Here, we study the dynamics and the coherence properties of a GaAs/AlGaAs double quantum dot charge qubit strongly coupled to a frequency-tunable high-impedance resonator. We drive qubit transitions with synthesized microwave pulses and perform qubit readout through the state-dependent frequency shift imparted by the qubit on the dispersively coupled resonator. We perform Rabi oscillation, Ramsey fringe, energy relaxation, and Hahn-echo measurements and find significantly reduced decoherence rates down to γ_{2}/2π∼3 MHz corresponding to coherence times of up to T_{2}∼50 ns for charge states in gate-defined quantum dot qubits. We realize Rabi π pulses of width down to σ∼0.25 ns.
This thesis investigates hybrid circuit quantum electrodynamics (cQED) as a versatile platform that unites superconducting resonators with semiconductor quantum dots. The central motivation is to harness strong light-matter coupling at the single-photon level, which enables coherent photon-qubit interactions and paves the way for quantum technologies in computation, communication, and sensing. The first part of this work combines hybrid cQED with holes in planar Ge/SiGe, a material system that has only recently become accessible for quantum devices. Planar Ge offers unique advantages for this purpose and has attracted considerable attention in the context of quantum computing. In contrast, its potential for hybrid cQED has remained largely unexplored, making the present work one of the first demonstrations of strong light-matter interaction in this platform. Within this framework, we demonstrate strong charge-photon coupling in planar Ge by observing vacuum Rabi splitting between a hole charge qubit based on a double quantum dot (DQD) and a microwave resonator. We employ a frequency-tunable high-impedance resonator to perform qubit spectroscopy, enabling systematic exploration of coupling regimes and confirming device controllability. In addition, we use this setup to carry out excited-state spectroscopy of strongly correlated states in the DQD, revealing the formation of Wigner molecules and illustrating how the hybrid architecture can be harnessed to access many-body physics. While these experiments in Ge demonstrate how strong coupling can be harnessed to explore qubit physics and correlated states, they also exemplify the wider potential of hybrid cQED. A particularly pressing application is in quantum optics, where efficient single-photon detectors are still lacking in the microwave regime. Such detectors are essential for enabling experiments in quantum communication and microwave quantum optics. In the second part of this thesis, we address this challenge by realizing a photodetector based on a GaAs DQD coupled to a superconducting resonator. The detector operates via photon-to-charge conversion and achieves efficiencies approaching unity. Strong coupling plays a central role by ensuring that incoming photons are absorbed before being lost to the environment, which is key to the high performance of the detector. We further exploit the frequency tunability of the resonator to investigate device performance and identify the parameters that optimize detection efficiency. The broader impact of this work lies in advancing quantum technologies that rely on coherent microwave photons. Applications include spin qubit readout, long-distance photon-mediated coupling, quantum communication, and microwave quantum optics. Looking forward, planar Ge is identified as a highly competitive platform for hybrid cQED. Future directions include the development of single-photon sources, quantum- limited detectors, and analog quantum simulators based on engineered resonator-qubit arrays.
High-efficiency single-photon detection in the microwave domain is a key enabling technology for various quantum applications. However, the extremely low energy of microwave photons presents a fundamental challenge, preventing direct photon-to-charge conversion as achieved in optical systems using semiconductors. Here, we demonstrate continuous microwave photon detection with an efficiency approaching 70% in the single-photon regime. We use a hybrid system comprising a gate-defined double quantum dot (DQD) charge qubit in a gallium arsenide/aluminum gallium arsenide heterostructure, coupled to a high-impedance Josephson junction array cavity. We systematically optimize the hybrid architecture to maximize the detection efficiency by leveraging strong charge-photon coupling, tunable DQD tunnel rates, and the frequency tunability of both subsystems. The system efficiency is characterized over a frequency range of 3 to 5.2 gigahertz. Our results establish semiconductor-based cavity-quantum electrodynamics architectures as a scalable and versatile platform for efficient microwave photon detection, opening promising avenues for quantum microwave optics and quantum information technologies.
High-efficiency single-photon detection in the microwave domain is a key enabling technology for various quantum applications. However, the extremely low energy of microwave photons presents a fundamental challenge, preventing direct photon-to-charge conversion as achieved in optical systems using semiconductors. Here, we demonstrate continuous microwave photon detection with an efficiency approaching 70% in the single-photon regime. We use a hybrid system comprising a gate-defined double quantum dot (DQD) charge qubit in a gallium arsenide/aluminum gallium arsenide heterostructure, coupled to a high-impedance Josephson junction array cavity. We systematically optimize the hybrid architecture to maximize the detection efficiency by leveraging strong charge-photon coupling, tunable DQD tunnel rates, and the frequency tunability of both subsystems. The system efficiency is characterized over a frequency range of 3 to 5.2 gigahertz. Our results establish semiconductor-based cavity-quantum electrodynamics architectures as a scalable and versatile platform for efficient microwave photon detection, opening promising avenues for quantum microwave optics and quantum information technologies.