A Traveling-Wave Parametric Amplifier With Integrated Diplexers

Abstract

Traveling-Wave Parametric Amplifiers (TWPAs) are ubiquitous in superconducting circuit readout, providing high gain with near-quantum-limited noise performance across a wide bandwidth. Their operation, however, relies on a strong microwave pump tone that is typically delivered using off-chip passive components, such as directional couplers or diplexers. These external elements add loss, increase system complexity, and limit scalability. Here, we present a traveling-wave parametric amplifier that incorporates on-chip input and output diplexers for pump routing. This co-fabricated architecture offers a compact and scalable solution for superconducting-circuit readout.

Figures (7)

• Figure 1: An overview of the D-TWPA integrated layout. (a) The TWPA is connected to the common port of a diplexer on each end. (b) The resulting chip has four microwave ports, along with the packaged device (c). The phase-matching resonator (d) and the lumped-element diplexers (f) are shown in false color micrographs, along with their corresponding equivalent schematics, (e) and (g) respectively.
• Figure 2: Gain and insertion loss measurements relative to a through reference. With the pump off (a) the crossover of the diplexer appears at $8.5$ GHz, and the resonant phase matching feature is just above $9$ GHz. (b) The gain profile with a pump optimized for noise performance ($9.06$ GHz and $-76.8$ dBm) is measured through both $S_{21}$ (blue curve) and $S_{43}$ (orange curve). Predicted scattering from simulations neglecting internal loss and early junction switching are show in light blue and orange, in good agreeement with the measurements.
• Figure 3: Measurement of the chain-added noise where the TWPA is the first amplifier. (a) The chain-added noise between $5.5$ GHz and $8.5$ GHz is shown for three different TWPA gains increasing from light purple to dark blue.. (b) Focusing on a frequency bin centered at $7.74$ GHz, the chain-added noise decreases as the TWPA gain increases, until it increases again at higher pump powers These measurements (squares) were excluded from the fit used to extract $N_\mathrm{TWPA}$.
• Figure 4: Full schematic of the experimental setup used to characterize the D-TWPA.
• Figure 5: The calibrated input attenuation as a function of frequency from the VNA to the TWPA input reference plane was determined using the SNTJ as a calibrated power source.