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arXiv:2311.11496 · Physical Review Applied

Selective single- and double-mode quantum-limited amplifier

Abdul Mohamed, Elham Zohari, Jarryd J. Pla, Paul E. Barclay, Shabir Barzanjeh

Published Jun 24, 2024• 6 citations
arXivHTMLPDF

Abstract

A quantum-limited amplifier enables the amplification of weak signals while introducing minimal noise dictated by the principles of quantum mechanics. Such amplifiers serve a broad spectrum of applications in quantum computing, including fast and accurate readout of superconducting qubits and spins, as well as various uses in quantum sensing and metrology. Parametric amplification, primarily developed with use of Josephson junctions, has evolved into the leading technology for highly effective microwave measurements within quantum circuits. Despite their significant contributions, these amplifiers face fundamental limitations, such as their inability to handle high powers, their sensitivity to parasitic magnetic fields, and particularly their limitation to operate only at millikelvin temperatures. To tackle these challenges, here we experimentally develop a novel quantum-limited amplifier based on superconducting kinetic inductance and present an extensive theoretical model to describe this nonlinear coupled-mode system. Our device surpasses the conventional constraints associated with Josephson-junction amplifiers by operating at much higher temperatures up to 4.5 K. With two distinct spectral modes and tunability through bias current, this amplifier can operate selectively in both the single-mode-amplification regime and the double-mode-amplification regime near the quantum noise limit. Using a nonlinear thin film exhibiting kinetic inductance, our device attains gain exceeding 50 dB in a single-mode configuration and 32 dB in a double-mode configuration, while adding 0.82 input-referred noise quanta. Importantly, this amplifier eliminates the need for Josephson junctions, resulting in the capability to handle significantly higher powers than Josephson junction--based amplifiers. It also demonstrates resilience in the presence of magnetic fields, offers a straightforward design, and increases reliability. This positions the amplifier as a versatile solution for quantum applications and facilitates its integration into future superconducting quantum computers.

DOI
10.1103/physrevapplied.21.064052

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A quantum-limited amplifier enables the amplification of weak signals while introducing minimal noise dictated by the principles of quantum mechanics. Such amplifiers serve a broad spectrum of applications in quantum computing, including fast and accurate readout of superconducting qubits and spins, as well as various uses in quantum sensing and metrology. Parametric amplification, primarily developed with use of Josephson junctions, has evolved into the leading technology for highly effective microwave measurements within quantum circuits. Despite their significant contributions, these amplifiers face fundamental limitations, such as their inability to handle high powers, their sensitivity to parasitic magnetic fields, and particularly their limitation to operate only at millikelvin temperatures. To tackle these challenges, here we experimentally develop a novel quantum-limited amplifier based on superconducting kinetic inductance and present an extensive theoretical model to describe this nonlinear coupled-mode system. Our device surpasses the conventional constraints associated with Josephson-junction amplifiers by operating at much higher temperatures up to 4.5 K. With two distinct spectral modes and tunability through bias current, this amplifier can operate selectively in both the single-mode-amplification regime and the double-mode-amplification regime near the quantum noise limit. Using a nonlinear thin film exhibiting kinetic inductance, our device attains gain exceeding 50 dB in a single-mode configuration and 32 dB in a double-mode configuration, while adding 0.82 input-referred noise quanta. Importantly, this amplifier eliminates the need for Josephson junctions, resulting in the capability to handle significantly higher powers than Josephson junction--based amplifiers. It also demonstrates resilience in the presence of magnetic fields, offers a straightforward design, and increases reliability. This positions the amplifier as a versatile solution for quantum applications and facilitates its integration into future superconducting quantum computers.
Parametric amplification is essential for quantum measurement, enabling the amplification of weak microwave signals with minimal added noise. While Josephson-junction-based amplifiers have become standard in superconducting quantum circuits, their magnetic sensitivity, limited saturation power, and sub-kelvin operating requirements motivate the development of alternative nonlinear platforms. Here we demonstrate a two-mode kinetic-inductance parametric amplifier based on a pair of capacitively coupled Kerr-nonlinear resonators fabricated from NbTiN and NbN thin films. The distributed Kerr nonlinearity of these materials enables nondegenerate four-wave-mixing amplification with gains approaching 40 dB, gain-bandwidth products up to 6.9 MHz, and 1-dB compression powers two to three orders of magnitude higher than those of state-of-the-art Josephson amplifiers. A coupled-mode theoretical model accurately captures the pump-induced modification of the hybridized modes and quantitatively reproduces the observed signal and idler responses. The NbN device exhibits a significantly larger Kerr coefficient and superior gain-bandwidth performance, highlighting the advantages of high-kinetic-inductance materials. Our results establish coupled kinetic-inductance resonators as a robust platform for broadband, high-power, and magnetically resilient quantum-limited amplification, offering a scalable route for advanced readout in superconducting qubits, spin ensembles, quantum dots, and other microwave-quantum technologies.
Superconducting parametric amplifiers are crucial components in microwave quantum circuits for enabling quantum-limited signal readout.The best-performing such amplifiers are often based on Josephson junctions, which however are sensitive to magnetic fields.Therefore, they require magnetic shields and are not easily integratable with other quantum systems that operate within magnetic fields, such as spinensemble quantum memories.To tackle this challenge, we develop a kinetic inductance-based parametric amplifier featuring a NbN nanobridge instead of Josephson junctions, which provides the desired nonlinearity for a strong parametric gain up to 42 dB.The added noise of this nanobridge kinetic-inductance parametric amplifier (hereby referred to as NKPA) is calibrated and found to be 0.59 ± 0.03 quanta for phase-preserving amplification, approaching the quantum limit of 0.5 quanta.Most importantly, we show that such excellent noise performance is preserved in an in-plane magnetic field up to 427 mT, the maximum field available in our experiment.This magnetic-field-resilient parametric amplifier presents an opportunity towards addressing single electron-spin resonance and more efficient search for axions as well as Majorana fermions.
Advancing superconducting quantum devices to higher operating frequencies broadens their functionality and enables operation at elevated temperatures, but it also requires near-quantum-limited amplifiers beyond the few-gigahertz regime. Here we present a junction-free, kinetic-inductance parametric amplifier based on thin-film niobium nitride (NbN) operating at 23 GHz in the microwave K-band, achieving a gain up to 40 dB, a 100 MHz gain-bandwidth product, a 1 dB saturation input power of -85 dBm with 23 dB gain, and added noise no greater than 1.4 quanta for phase-preserving amplification. Leveraging the large superconducting gap of NbN, this architecture can be extended to even higher frequencies, supporting applications such as high-fidelity readout of millimeter-wave superconducting qubits and axion searches over an expanded mass window.
Superconducting microwave amplifiers are essential for sensitive signal readout in superconducting quantum processors. Typically based on Josephson junctions, these amplifiers require operation at milli-Kelvin temperatures to achieve quantum-limited performance. Here, we demonstrate a quantum microwave amplifier that employs radiative cooling to operate at elevated temperatures and maintain near quantum-limited added noise. This kinetic-inductance-based parametric amplifier, patterned from a single layer of relatively high-Tc NbN thin film, maintains a high gain and meanwhile enables low added noise of 1.3 quanta when operated at 1.5 K. Remarkably, this represents only a 0.2 quanta increase compared to the performance at a base temperature of 0.1 K. Based on our findings, we also discuss the practicality of such an operating scheme for various quantum applications. By uplifting the parametric amplifiers from the mixing chamber without compromising readout efficiency, this work represents an important step toward more scalable microwave quantum technologies.
Advancing superconducting quantum devices to higher operating frequencies broadens their functionality and enables operation at elevated temperatures, but it also requires near-quantum-limited amplifiers beyond the few-gigahertz regime. Here, we present a junction-free, kinetic-inductance parametric amplifier based on thin-film niobium nitride (NbN) operating at 23 GHz in the microwave K-band, achieving a gain up to 40 dB, a 100 MHz gain–bandwidth product, a 1 dB saturation input power of −85 dBm with 23 dB gain, and added noise not greater than 1.4 quanta for phase-preserving amplification. Leveraging the large superconducting gap of NbN, this architecture can be extended to even higher frequencies, supporting applications such as high-fidelity readout of millimeter-wave superconducting qubits and axion searches over an expanded mass window.
Microwave parametric amplifiers operating at the quantum noise limit have become indispensable tools for a range of cryogenic quantum technologies. These amplifiers are typically constructed from nonlinear Josephson junctions, which limit the ability to amplify high-power signals. This study reports a device based instead on the weakly nonlinear kinetic inductance intrinsic to a superconducting film of niobium titanium nitride. The amplifier offers large phase-sensitive gain and high power handling, plus a simple design and fabrication process. As it contains no junctions, it is robust to electrostatic discharge and potentially operable under high temperatures and large magnetic fields.