Traveling wave parametric amplifier with Josephson junctions using minimal resonator phase matching

Abstract

Josephson parametric amplifiers have become a critical tool in superconducting device physics due to their high gain and quantum-limited noise. Traveling wave parametric amplifiers (TWPAs) promise similar noise performance while allowing for significant increases in both bandwidth and dynamic range. We present a TWPA device based on an LC-ladder transmission line of Josephson junctions and parallel plate capacitors using low-loss amorphous silicon dielectric. Crucially, we have inserted λ/4 resonators at regular intervals along the transmission line in order to maintain the phase matching condition between pump, signal, and idler and increase gain. We achieve an average gain of 12 dB across a 4 GHz span, along with an average saturation power of -92 dBm with noise approaching the quantum limit.The Josephson parametric amplifier [1][2][3][4][5][6][7] (JPA) is a critical tool for high fidelity state measurement in superconducting qubits [8][9][10] as it allows parametric amplification with near quantum-limited noise [11]. Despite its success, the JPA has typically been used only for single frequency measurements due to lower bandwidth and saturation power. A promising approach to scaling superconducting qubit experiments is frequency multiplexing [12][13][14], which requires additional bandwidth and dynamic range for each measurement tone. Simultaneous amplification of up to five multiplexed tones has been achieved with a JPA [15-17] but was only possible with the Impedance-transformed parametric amplifier [18] (IMPA). This highly engineered JPA provides much larger bandwidth and saturation power but pushes the resonant design to its low Q limit.To extend this frequency multiplexed approach for future experiments, we have adopted the distributed design of the traveling wave parametric amplifier (TWPA) [19]. Fiber-optic TWPAs have already demonstrated high gain, dynamic range, and bandwidth while reaching the quantum-limit of added noise [20,21]. In this letter we present a microwave frequency TWPA with 4 GHz of bandwidth and an order of magnitude more saturation power than the best JPA. This device is compatible with scaling to much larger qubit systems through multiplexed measurement, and may find applications outside quantum information such as astrophysics detectors [12,22] At microwave frequencies the TWPA can be thought of as a transmission line where the propagation velocity is controlled by varying the individual circuit parameters of inductance or capacitance per unit length [24,25]. This is typically achieved by constructing a signal line with a current dependent (nonlinear) inductance. Like the JPA, a large enough pump tone will modulate this inductance, coupling the pump (ω p ) to a signal (ω s ) and idler (ω i ) tone via frequency mixing such that ω s + ω i = 2ω p . Unlike the JPA however, the TWPA has no resonant structure so gain, bandwidth, and dynamic range are determined by the coupled mode equations of a nonlinear transmission line [23]. In addition to allowing more bandwidth and saturation power...

Broadband parametric amplification with impedance engineering: Beyond the gain-bandwidth product

“…While the observed large bandwidth was qualitatively explained by a model consisting of a negative resistance 18 coupled to a frequency dependent impedance, no clear prescription on the design principle was provided. A different approach using Josephson non-linear transmission lines 19,20 was recently demonstrated 21,22 with nearly 4 GHz of bandwidth. However, this design requires fabrication of about 2000 nearly identical blocks of oscillator stages, demanding fairly sophisticated fabrication facilities.…”

Hysteretic Flux Response and Nondegenerate Gain of Flux-Driven Josephson Parametric Amplifiers

“…However, the operation of SQCs often requires quantumlimited amplification of weak signals over a broad frequency range. For this purpose, one can either use broadband traveling wave parametric amplifiers [1,2] or band tunable narrow-band JPAs [3][4][5][6]. The latter are nowadays routinely used to provide amplification with a noise performance close to the standard quantum limit [7][8][9][10][11][12].…”

Broadband parametric amplifiers based on nonlinear kinetic inductance artificial transmission lines

“…In this manner, the phase mismatch accumulated along each section of nonlinear transmission line is countered by the phase shift introduced by the resonator. For a sufficient number of resonators, the structure approximates a transmission line with continuous dispersion, and phase-matched gain may be achieved [24].…”

“…2(a) shows an alternative phase-matching scheme based on resonator phase shifters embedded along the transmission line. This technique was demonstrated earlier for traveling-wave Josephson parametric amplifiers in [24]. To correct for the nonlinearity-induced phase mismatch, we periodically place resonators, with resonant frequency slightly above the desired pump f r f p , along the transmission line.…”