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

Josephson-kanavatransistori-pohjaisten parametrivahvistimien suunnittelu ja simulaatio

Juulia Kirjavainen

Published Dec 11, 2025• 0 citations
OpenAlex

Abstract

Cryogenic, ultralow-noise microwave amplification is critical in superconducting qubit readout, microwave detection, and space technology. Josephson parametric amplifiers (JPAs) are widely used in microwave amplification. Parametric amplification occurs because a nonlinear element and a strong pump enable frequency mixing. The core component of a JPA is a Josephson junction, which acts as a nonlinear inductor and is formed by a thin layer of insulator or normal metal sandwiched between two superconductors. However, gate-controlled Josephson field-effect transistors (JoFETs) have been less studied in this context. In particular, graphene-based JoFETs have shown promising results in terms of scalability and electrostatic control, which could provide an alternative to magnetic field control. The aim of this thesis is to study graphene-based JoFETs as a nonlinear element in superconducting parametric amplifiers. The study was carried out as a literature review and circuit-level simulations using Keysight Advanced Design System (ADS) software. At first, an LC resonator-based JPA was implemented, in which the nonlinear element was a Verilog-A model of a nonlinear Josephson inductance. Harmonic balance (HB) simulation was performed to study the bandwidth, and gain as a function of signal frequency and the dependence on pump power. It showed that parametric gain occurs only when the pump is on. 30 dB gain and 290 MHz bandwidth were achieved. As the gain increased, the bandwidth became narrower. Finally, a gate-pumped JPA using a JoFET was simulated. The JoFET was implemented using a Verilog-A model, which was based on measurements by VTT of their graphene JoFETs. HB simulations showed the electrostatic control of the gate-pumped JPA and gain-bandwidth trade-off typical of JPAs. 15–35 dB gain and 150 MHz bandwidth were obtained, and the resonance frequency could be adjusted with the DC gate voltage. Overall, the observed behavior corresponds well with the reported results for JPAs and fabricated JoFET JPAs. These findings suggest that graphene JoFETs enable parametric gain that can be controlled electrostatically. Although their noise levels may not meet the requirements of quantum computers, they could be useful in other demanding applications, such as space technology.

Related papers

Graphene-based superconducting quantum circuits : the Josephson parametric amplifier

Guilliam Butseraen

With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to dramatic advances in microwave quantum optics. Of these elements, quantum-limited parametric amplifiers have proven to be essential for low noise readout of quantum systems whose energy range is intrinsically low (tens of µeV). They are also used to generate non classical states of light that can be a resource for quantum enhanced detection. Superconducting parametric amplifiers, like quantum bits, typically utilize a Josephson junction as a source of magnetically tunable and dissipation-free nonlinearity. The magnetic control is not an industry standard for devices and starts already to be an issue in large scale circuits. In recent years, efforts have been made to introduce semiconductor weak links as electrically tunable nonlinear elements, with demonstrations of microwave resonators and quantum bits using semiconductor nanowires, a two dimensional electron gas, carbon nanotubes and graphene. However, given the challenge of balancing nonlinearity, dissipation, participation, and energy scale, parametric amplifiers have not yet been implemented with a semiconductor weak link. The work presented in this PhD thesis demonstrates the design, fabrication and performances of a parametric amplifier leveraging a graphene Josephson junction.The graphene is encapsulated in between hBN flakes in order to improve its quality. Using such high quality junctions, we demonstrate amplification with 20 dB gain which is the milestone for overcoming noise of the classical amplifiers in the rest of the amplification chain. The Josephson parametric amplifier being based on a resonant structure (around 6 GHz) suffers from the gain bandwidth product limiting the amplification to a few MegaHertz frequency range. The use of a side gate to electrically tune the graphene gives control of the Josephson junction inductance and thus the resonant frequency of the amplifier. We demonstrate a near 1 GHz tunability of the amplification frequency with the use of a side gate which is as good as the tunability offered by using a magnetic flux on a SQUID for similar amplifier designs. Moreover, graphene has shown to exhibit nonlinear loss under a strong microwave irradiation arising because of dynamics in the Andreev states. Dissipation is known to add intrinsic noise on quantum amplifiers and could be a problem for quantum limited parametric amplification. We demonstrate that despite the presence of nonlinear loss, graphene based Josephson parametric amplifiers can reach near quantum limited amplification. A two photon loss model was used to describe the behaviour of the device but we show that a more complex model is required in order to take into account the nonlinear dissipation and the non-sinusoidal current phase relation. We also studied the dynamic range and showed that the graphene based Josephson parametric amplifier can reach a 1 dB compression point of -123 dBm which is as good as single tunnel junctions based parametric amplifiers. Our results expand the toolset for electrically tunable superconducting quantum circuits and offer new opportunities for the development of quantum technologies such as quantum computing, quantum sensing and fundamental science.

•Nov 8, 2022•0 citations

Quantum noise limited microwave amplification using a graphene Josephson junction

Joydip Sarkar, Kishor V. Salunkhe, Supriya Mandal +7 more

Josephson junctions (JJ) and their tunable properties, including their nonlinearities, form the core of superconducting circuit quantum electrodynamics (cQED). In quantum circuits, low-noise amplification of feeble microwave signals is essential and the Josephson parametric amplifiers (JPA) are the widely used devices. The existing JPAs are based on Al-AlOx-Al tunnel junctions realized in a superconducting quantum interference device geometry, where magnetic flux is the knob for tuning the frequency. Recent experimental realizations of 2D van der Waals JJs provide an opportunity to implement various cQED devices with the added advantage of tuning the junction properties and the operating point using a gate potential. While other components of a possible 2D van der Waals cQED architecture have been demonstrated -- quantum noise limited amplifier, an essential component, has not been realized. Here we implement a quantum noise limited JPA, using a graphene JJ, that has linear resonance gate tunability of 3.5 GHz. We report 24 dB amplification with 10 MHz bandwidth and -130 dBm saturation power; performance on par with the best single-junction JPAs. Importantly, our gate tunable JPA works in the quantum-limited noise regime which makes it an attractive option for highly sensitive signal processing. Our work has implications for novel bolometers -- the low heat capacity of graphene together with JJ nonlinearity can result in an extremely sensitive microwave bolometer embedded inside a quantum noise-limited amplifier. In general, our work will open up exploration of scalable device architecture of 2D van der Waals materials by integrating a sensor with the quantum amplifier.

arXiv:2204.02103•Apr 5, 2022•3 citations

Josephsonin parametrivahvistimen kehittäminen keskitetyillä elementeillä alle 1 GHz:n taajuuksia varten

Räisänen, Ilmo

It is important to measure temperature fast and accurately in many experiments in low-temperature physics and nanophysics. The accuracy of the measurement is compromised by noise. A Josephson parametric amplifier (JPA) can provide us with low-noise amplification in the microwave frequency range (300 MHz - 30 GHz) for, e.g., radio frequency thermometry and radiation detection. This Master's thesis presents a lumped element JPA made in collaboration by Aalto University and VTT and reports its refection coefficient, gain, bandwidth, 1 dB compression point, noise temperature and quality factors. Experimental results are compared with nonlinear circuit simulations done with APLAC, which gives us information about component properties for fabrication of a new device. Reflection coefficient measurement gives us the resonance frequency (642.0 MHz) and the bifurcation frequency (640.2 MHz) of the JPA. Gain measurement reveals the maximal gain (26.2 dB), the optimal operating frequency (641.3 MHz) and the optimal pump power (-96 dBm). The gain-bandwidth product is simulated as a function of coupling capacitance and pump power and it is observed to be lower than what theory suggests. The noise temperature of the JPA is measured to be between 1 K and 4 K in thefrequency range 639.25 MHz ... 640.45 MHz according to both the Y-factor method and the signal-to-noise ratio (SNR) method, but according to the SNR method the noise temperature is roughly 50 % lower than according to the Y-factor method. When the pump generator is off, the noise temperature of the system is between 25 K and 80 K in the frequency range 639.15 MHz ... 640.30 MHz according to the SNR method.

•May 12, 2015•0 citations

Development and characterization of a flux-pumped lumped element Josephson parametric amplifier

Martina Esposito, Joseph Rahamim, Andrew Patterson +11 more

Josephson parametric amplification is a tool of paramount importance in circuit-QED especially for the quantum-noise-limited single-shot read-out of superconducting qubits. We developed a Josephson parametric amplifier (JPA) based on a lumped-element LC resonator, in which the inductance L is composed by a geometric inductance and an array of 4 superconducting quantum interference devices (SQUIDs). We characterized the main figures of merit of the device, obtaining a −3 dB bandwidth BW = 15 MHz for a gain G = 21 dB and a 1 dB compression point P1dB = −115 dBm. The obtained results are promising for the future use of such JPA as the first stage of amplification for single-shot readout of superconducting qubits.

EPJ Web of Conferences•Jan 1, 2019•4 citations

Quantum Dot-Based Parametric Amplifiers

Laurence Cochrane, Theodor Lundberg, David J. Ibberson +8 more

Josephson parametric amplifiers (JPAs) approaching quantum-limited noise performance have been instrumental in enabling high fidelity readout of superconducting qubits and, recently, semiconductor quantum dots (QDs). We propose that the quantum capacitance arising in electronic two-level systems (the dual of Josephson inductance) can provide an alternative dissipation-less non-linear element for parametric amplification. We experimentally demonstrate phase-sensitive parametric amplification using a QD-reservoir electron transition in a CMOS nanowire split-gate transistor embedded in a 1.8~GHz superconducting lumped-element microwave cavity, achieving parametric gains of -3 to +3 dB, limited by Sisyphus dissipation. Using a semi-classical model, we find an optimised design within current technological capabilities could achieve gains and bandwidths comparable to JPAs, while providing complementary specifications with respect to integration in semiconductor platforms or operation at higher magnetic fields.

arXiv:2111.11825•Nov 23, 2021•1 citation

Fabrication of the Impedance-Matched Josephson Parametric Amplifier and the Study of the Gain Profile

Rui Liang Yang, Huiqiu Deng

We designed and fabricated an impedance-matched Josephson parametric amplifier (JPA) working in the flux-pump mode for the broadband amplification of microwave signals. A simple fabrication method suitable for a small cleanroom was developed. We also studied the phase response, as well as the gain, as a function of signal frequency and pump power at various pump frequencies. The phase response can be explained with the behavior of the nonlinear Duffing oscillator. The observed decrease of the resonance frequency as the pump power increases, as well as the emergence of an unstable bifurcation zone, are the characteristic nonlinear behavior of the Duffing oscillator. The features of the gain profile in the stable zone can be explained with a model adapted from the theoretical model for the two-dimensional gain profile of an impedance-matched, current-pumped JPA. Over 17 dB gain with a bandwidth more than 300 MHz (centered around 6.45 GHz) was observed. Our impedance-matched JPA is used for improving the fast readout fidelity of transmon qubits.

arXiv:1909.00707•IEEE Transactions on Applied Superconductivity•Apr 6, 2020•14 citations
Cryogenic, ultralow-noise microwave amplification is critical in superconducting qubit readout, microwave detection, and space technology. Josephson parametric amplifiers (JPAs) are widely used in microwave amplification. Parametric amplification occurs because a nonlinear element and a strong pump enable frequency mixing. The core component of a JPA is a Josephson junction, which acts as a nonlinear inductor and is formed by a thin layer of insulator or normal metal sandwiched between two superconductors. However, gate-controlled Josephson field-effect transistors (JoFETs) have been less studied in this context. In particular, graphene-based JoFETs have shown promising results in terms of scalability and electrostatic control, which could provide an alternative to magnetic field control. The aim of this thesis is to study graphene-based JoFETs as a nonlinear element in superconducting parametric amplifiers. The study was carried out as a literature review and circuit-level simulations using Keysight Advanced Design System (ADS) software. At first, an LC resonator-based JPA was implemented, in which the nonlinear element was a Verilog-A model of a nonlinear Josephson inductance. Harmonic balance (HB) simulation was performed to study the bandwidth, and gain as a function of signal frequency and the dependence on pump power. It showed that parametric gain occurs only when the pump is on. 30 dB gain and 290 MHz bandwidth were achieved. As the gain increased, the bandwidth became narrower. Finally, a gate-pumped JPA using a JoFET was simulated. The JoFET was implemented using a Verilog-A model, which was based on measurements by VTT of their graphene JoFETs. HB simulations showed the electrostatic control of the gate-pumped JPA and gain-bandwidth trade-off typical of JPAs. 15–35 dB gain and 150 MHz bandwidth were obtained, and the resonance frequency could be adjusted with the DC gate voltage. Overall, the observed behavior corresponds well with the reported results for JPAs and fabricated JoFET JPAs. These findings suggest that graphene JoFETs enable parametric gain that can be controlled electrostatically. Although their noise levels may not meet the requirements of quantum computers, they could be useful in other demanding applications, such as space technology.
With a large portfolio of elemental quantum components, superconducting quantum circuits have contributed to dramatic advances in microwave quantum optics. Of these elements, quantum-limited parametric amplifiers have proven to be essential for low noise readout of quantum systems whose energy range is intrinsically low (tens of µeV). They are also used to generate non classical states of light that can be a resource for quantum enhanced detection. Superconducting parametric amplifiers, like quantum bits, typically utilize a Josephson junction as a source of magnetically tunable and dissipation-free nonlinearity. The magnetic control is not an industry standard for devices and starts already to be an issue in large scale circuits. In recent years, efforts have been made to introduce semiconductor weak links as electrically tunable nonlinear elements, with demonstrations of microwave resonators and quantum bits using semiconductor nanowires, a two dimensional electron gas, carbon nanotubes and graphene. However, given the challenge of balancing nonlinearity, dissipation, participation, and energy scale, parametric amplifiers have not yet been implemented with a semiconductor weak link. The work presented in this PhD thesis demonstrates the design, fabrication and performances of a parametric amplifier leveraging a graphene Josephson junction.The graphene is encapsulated in between hBN flakes in order to improve its quality. Using such high quality junctions, we demonstrate amplification with 20 dB gain which is the milestone for overcoming noise of the classical amplifiers in the rest of the amplification chain. The Josephson parametric amplifier being based on a resonant structure (around 6 GHz) suffers from the gain bandwidth product limiting the amplification to a few MegaHertz frequency range. The use of a side gate to electrically tune the graphene gives control of the Josephson junction inductance and thus the resonant frequency of the amplifier. We demonstrate a near 1 GHz tunability of the amplification frequency with the use of a side gate which is as good as the tunability offered by using a magnetic flux on a SQUID for similar amplifier designs. Moreover, graphene has shown to exhibit nonlinear loss under a strong microwave irradiation arising because of dynamics in the Andreev states. Dissipation is known to add intrinsic noise on quantum amplifiers and could be a problem for quantum limited parametric amplification. We demonstrate that despite the presence of nonlinear loss, graphene based Josephson parametric amplifiers can reach near quantum limited amplification. A two photon loss model was used to describe the behaviour of the device but we show that a more complex model is required in order to take into account the nonlinear dissipation and the non-sinusoidal current phase relation. We also studied the dynamic range and showed that the graphene based Josephson parametric amplifier can reach a 1 dB compression point of -123 dBm which is as good as single tunnel junctions based parametric amplifiers. Our results expand the toolset for electrically tunable superconducting quantum circuits and offer new opportunities for the development of quantum technologies such as quantum computing, quantum sensing and fundamental science.
Josephson junctions (JJ) and their tunable properties, including their nonlinearities, form the core of superconducting circuit quantum electrodynamics (cQED). In quantum circuits, low-noise amplification of feeble microwave signals is essential and the Josephson parametric amplifiers (JPA) are the widely used devices. The existing JPAs are based on Al-AlOx-Al tunnel junctions realized in a superconducting quantum interference device geometry, where magnetic flux is the knob for tuning the frequency. Recent experimental realizations of 2D van der Waals JJs provide an opportunity to implement various cQED devices with the added advantage of tuning the junction properties and the operating point using a gate potential. While other components of a possible 2D van der Waals cQED architecture have been demonstrated -- quantum noise limited amplifier, an essential component, has not been realized. Here we implement a quantum noise limited JPA, using a graphene JJ, that has linear resonance gate tunability of 3.5 GHz. We report 24 dB amplification with 10 MHz bandwidth and -130 dBm saturation power; performance on par with the best single-junction JPAs. Importantly, our gate tunable JPA works in the quantum-limited noise regime which makes it an attractive option for highly sensitive signal processing. Our work has implications for novel bolometers -- the low heat capacity of graphene together with JJ nonlinearity can result in an extremely sensitive microwave bolometer embedded inside a quantum noise-limited amplifier. In general, our work will open up exploration of scalable device architecture of 2D van der Waals materials by integrating a sensor with the quantum amplifier.
It is important to measure temperature fast and accurately in many experiments in low-temperature physics and nanophysics. The accuracy of the measurement is compromised by noise. A Josephson parametric amplifier (JPA) can provide us with low-noise amplification in the microwave frequency range (300 MHz - 30 GHz) for, e.g., radio frequency thermometry and radiation detection. This Master's thesis presents a lumped element JPA made in collaboration by Aalto University and VTT and reports its refection coefficient, gain, bandwidth, 1 dB compression point, noise temperature and quality factors. Experimental results are compared with nonlinear circuit simulations done with APLAC, which gives us information about component properties for fabrication of a new device. Reflection coefficient measurement gives us the resonance frequency (642.0 MHz) and the bifurcation frequency (640.2 MHz) of the JPA. Gain measurement reveals the maximal gain (26.2 dB), the optimal operating frequency (641.3 MHz) and the optimal pump power (-96 dBm). The gain-bandwidth product is simulated as a function of coupling capacitance and pump power and it is observed to be lower than what theory suggests. The noise temperature of the JPA is measured to be between 1 K and 4 K in thefrequency range 639.25 MHz ... 640.45 MHz according to both the Y-factor method and the signal-to-noise ratio (SNR) method, but according to the SNR method the noise temperature is roughly 50 % lower than according to the Y-factor method. When the pump generator is off, the noise temperature of the system is between 25 K and 80 K in the frequency range 639.15 MHz ... 640.30 MHz according to the SNR method.
Josephson parametric amplification is a tool of paramount importance in circuit-QED especially for the quantum-noise-limited single-shot read-out of superconducting qubits. We developed a Josephson parametric amplifier (JPA) based on a lumped-element LC resonator, in which the inductance L is composed by a geometric inductance and an array of 4 superconducting quantum interference devices (SQUIDs). We characterized the main figures of merit of the device, obtaining a −3 dB bandwidth BW = 15 MHz for a gain G = 21 dB and a 1 dB compression point P1dB = −115 dBm. The obtained results are promising for the future use of such JPA as the first stage of amplification for single-shot readout of superconducting qubits.
Josephson parametric amplifiers (JPAs) approaching quantum-limited noise performance have been instrumental in enabling high fidelity readout of superconducting qubits and, recently, semiconductor quantum dots (QDs). We propose that the quantum capacitance arising in electronic two-level systems (the dual of Josephson inductance) can provide an alternative dissipation-less non-linear element for parametric amplification. We experimentally demonstrate phase-sensitive parametric amplification using a QD-reservoir electron transition in a CMOS nanowire split-gate transistor embedded in a 1.8~GHz superconducting lumped-element microwave cavity, achieving parametric gains of -3 to +3 dB, limited by Sisyphus dissipation. Using a semi-classical model, we find an optimised design within current technological capabilities could achieve gains and bandwidths comparable to JPAs, while providing complementary specifications with respect to integration in semiconductor platforms or operation at higher magnetic fields.
We designed and fabricated an impedance-matched Josephson parametric amplifier (JPA) working in the flux-pump mode for the broadband amplification of microwave signals. A simple fabrication method suitable for a small cleanroom was developed. We also studied the phase response, as well as the gain, as a function of signal frequency and pump power at various pump frequencies. The phase response can be explained with the behavior of the nonlinear Duffing oscillator. The observed decrease of the resonance frequency as the pump power increases, as well as the emergence of an unstable bifurcation zone, are the characteristic nonlinear behavior of the Duffing oscillator. The features of the gain profile in the stable zone can be explained with a model adapted from the theoretical model for the two-dimensional gain profile of an impedance-matched, current-pumped JPA. Over 17 dB gain with a bandwidth more than 300 MHz (centered around 6.45 GHz) was observed. Our impedance-matched JPA is used for improving the fast readout fidelity of transmon qubits.