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Josephson traveling-wave parametric amplifier with magnetic flux drive

Alexander B Zorin

Published Apr 24, 2018• 0 citations
OpenAlex

Abstract

We have developed a concept of the traveling-wave parametric amplifier driven by external magnetic flux. The circuit consists of a serial array of symmetric dc SQUIDs coupled inductively to a separate superconducting LC-transmission line carrying the pump flux-wave. The adjusted phase velocity of the pump wave ensures efficient three wave mixing with the signal and the idler waves. Due to operation in the linear regime of the SQUIDs the matching condition for corresponding wave vectors can be fulfilled in this circuit with sufficiently high accuracy. This property enables large gain and wide bandwidth, whereas inherently minimal depletion of the pump ensures a large dynamic range. The experimental parameters and characteristics of this amplifier have been evaluated and shown great promise for the application in quantum information circuits.

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With potentially quantum limited performance and wide frequency bandwidth, traveling-wave Josephson parametric amplifiers (TWJPAs) based on superconducting circuits are in urgent demand for quantum information processing. This study designs a TWJPA in which the interacting pump and signal/idler microwaves propagate with similar phase velocities through two different transmission lines, thereby enabling parametric gain. Such operation is possible due to a chain of SQUIDs that form the signal transmission line, which is magnetically coupled to a separate pump $L\phantom{\rule{0}{0ex}}C$ line. The proposed circuit may greatly simplify the measurement setup and solve the problem of pump depletion.

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We develop a concept of traveling-wave Josephson parametric amplifier based on a ladder-type superconducting transmission line containing serial array of one-junctions SQUIDs. The circuit operates in a three-wave mixing mode and exploits both quadratic and cubic (Kerr) nonlinearities in the current-phase relation of the SQUIDs controlled by external magnetic flux. These two types of nonlinearities allow efficient three-wave mixing and perfect phase matching, respectively. The transmission line exhibits a power gain with exponential dependence on its length (number of cells $N$) in the widest frequency range, $0 \lesssim f_s, f_i \lesssim f_p$, where $f_s$, $f_i$ and $f_p$ are the signal, idler and pump frequencies, respectively, obeying relation $f_s + f_i = f_p$. Estimation of the amplifier characteristics with typical experimental parameters, number of cells $N$ = 700, length of 28 mm and pump frequency of 12.5 GHz yields a flat (-3 dB) gain of about 20 dB in the bandwidth from 3.35 GHz to 9.15 GHz and a saturation power of -90 dBm.

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We develop a novel concept of a Josephson traveling-wave parametric amplifier with three-wave mixing. The proposed amplifier consists of a microwave transmission line formed by a serial array of nonhysteretic one-junction SQUIDs. These SQUIDs are flux-biased such that the phase drops across the Josephson junctions are equal to 90°. This one-dimensional metamaterial possesses large quadratic nonlinearity and minimal cubic (Kerr-like) nonlinearity. This property allows phase matching and exponential power gain in a wide frequency range. The proof-of-principle measurements performed at temperature T = 4.2 K on Nb trilayer samples have demonstrated the validity of our concept of a practical Josephson parametric amplifier with great promise for quantum-limited performance.

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We have proposed a new design of the Josephson traveling-wave parametric amplifier (JTWPA) capable of providing much higher spurious-free dynamic range (SFDR). For this purpose, we substitute dc SQUIDs for bi-SQUIDs in the used artificial signal transmission line driven by external travelling-wave magnetic flux. The increase of SFDR follows from the increased linearity domain of the phase-current relation in bi-SQUID as compared to dc SQUID. Optimal parameters for bi-SQUIDs have been determined. The first version of JTWPA was modeled to be fabricated using niobium process.

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Instruments and Experimental Techniques•Oct 1, 2024•1 citation
We have developed a concept of the traveling-wave parametric amplifier driven by external magnetic flux. The circuit consists of a serial array of symmetric dc SQUIDs coupled inductively to a separate superconducting LC-transmission line carrying the pump flux-wave. The adjusted phase velocity of the pump wave ensures efficient three wave mixing with the signal and the idler waves. Due to operation in the linear regime of the SQUIDs the matching condition for corresponding wave vectors can be fulfilled in this circuit with sufficiently high accuracy. This property enables large gain and wide bandwidth, whereas inherently minimal depletion of the pump ensures a large dynamic range. The experimental parameters and characteristics of this amplifier have been evaluated and shown great promise for the application in quantum information circuits.
With potentially quantum limited performance and wide frequency bandwidth, traveling-wave Josephson parametric amplifiers (TWJPAs) based on superconducting circuits are in urgent demand for quantum information processing. This study designs a TWJPA in which the interacting pump and signal/idler microwaves propagate with similar phase velocities through two different transmission lines, thereby enabling parametric gain. Such operation is possible due to a chain of SQUIDs that form the signal transmission line, which is magnetically coupled to a separate pump $L\phantom{\rule{0}{0ex}}C$ line. The proposed circuit may greatly simplify the measurement setup and solve the problem of pump depletion.
We develop a concept of traveling-wave Josephson parametric amplifier based on a ladder-type superconducting transmission line containing serial array of one-junctions SQUIDs. The circuit operates in a three-wave mixing mode and exploits both quadratic and cubic (Kerr) nonlinearities in the current-phase relation of the SQUIDs controlled by external magnetic flux. These two types of nonlinearities allow efficient three-wave mixing and perfect phase matching, respectively. The transmission line exhibits a power gain with exponential dependence on its length (number of cells NNN) in the widest frequency range, 0≲fs,fi≲fp0 \lesssim f_s, f_i \lesssim f_p0≲fs​,fi​≲fp​, where fsf_sfs​, fif_ifi​ and fpf_pfp​ are the signal, idler and pump frequencies, respectively, obeying relation fs+fi=fpf_s + f_i = f_pfs​+fi​=fp​. Estimation of the amplifier characteristics with typical experimental parameters, number of cells NNN = 700, length of 28 mm and pump frequency of 12.5 GHz yields a flat (-3 dB) gain of about 20 dB in the bandwidth from 3.35 GHz to 9.15 GHz and a saturation power of -90 dBm.
We develop a novel concept of a Josephson traveling-wave parametric amplifier with three-wave mixing. The proposed amplifier consists of a microwave transmission line formed by a serial array of nonhysteretic one-junction SQUIDs. These SQUIDs are flux-biased such that the phase drops across the Josephson junctions are equal to 90°. This one-dimensional metamaterial possesses large quadratic nonlinearity and minimal cubic (Kerr-like) nonlinearity. This property allows phase matching and exponential power gain in a wide frequency range. The proof-of-principle measurements performed at temperature T = 4.2 K on Nb trilayer samples have demonstrated the validity of our concept of a practical Josephson parametric amplifier with great promise for quantum-limited performance.
We have proposed a new design of the Josephson traveling-wave parametric amplifier (JTWPA) capable of providing much higher spurious-free dynamic range (SFDR). For this purpose, we substitute dc SQUIDs for bi-SQUIDs in the used artificial signal transmission line driven by external travelling-wave magnetic flux. The increase of SFDR follows from the increased linearity domain of the phase-current relation in bi-SQUID as compared to dc SQUID. Optimal parameters for bi-SQUIDs have been determined. The first version of JTWPA was modeled to be fabricated using niobium process.
Abstract A Josephson traveling-wave parametric amplifier (JTWPA) is indispensable for the high-fidelity readout of superconducting qubits, owing to its broadband gain and near-quantum-limited noise performance. Conventional JTWPAs implemented with 0-Josephson junctions (0-JTWPAs) avoid magnetic-flux bias but rely on Kerr nonlinearity, which leads to pump-power-dependent phase mismatch, gain ripple, and a limited dynamic range. More recently, three-wave-mixing (3WM) JTWPAs employing flux-biased rf-SQUIDs have been proposed to suppress Kerr effects. However, these designs require a significant external flux bias per unit cell, which complicates cryogenic hardware, introduces sensitivity to flux noise, and limits scalability in large arrays. In this study, we propose and analyze a π -junction-based JTWPA ( π -JTWPA) in which the intrinsic π phase shift of the junction effectively displaces the operating point of the current–phase relation. This approach aims to realize 3WM-type nonlinearity with reduced flux bias while preserving broadband amplification, thereby simplifying flux-bias distribution, enhancing robustness against flux noise, and providing a pathway toward scalable, multiplexed quantum readout architectures. In addition, we examine the potential applicability of the π -JTWPA in four-wave-mixing (4WM) operation.
Abstract Josephson traveling wave parametric amplifiers can have high gain and wide frequency range, high sensitivity, and low noise, which makes them promising for quantum computing, array receiver readout systems, spectroscopy, single-photon detectors, etc. In this paper, the authors investigate samples of traveling wave parametric amplifiers based on a three-layer Nb/AlO x /Nb superconductor–insulator–superconductor (SIS) structure with a SNAIL (Superconducting Nonlinear Asymmetric Inductive Elements) series array. Each SNAIL cell consists of the kinetic inductance of four SIS junctions and the nonlinear inductance of a smaller SIS junction. The cells are alternately connected in antiphase with respect to the magnetic flux, which ensures a change in the sign of the Kerr nonlinearity and a reduction in the phase mismatch for the pump frequency, signal frequency, and idler frequency. The transmission spectra of the samples were measured at temperatures of 4.2 and 2.8 K in the frequency range of 0.1–6 GHz.