Broadband flux-pumped Josephson parametric amplifier with an on-chip coplanar waveguide impedance transformer

Abstract

The rapid progress towards scalable quantum processors demands amplifiers with large bandwidths and high saturation powers. For this purpose, we present a broadband flux-pumped Josephson parametric amplifier integrated with an on-chip coplanar waveguide impedance transformer. Our device can be fabricated with simple and straightforward photo-lithography. This device experimentally achieves an operational bandwidth over 600 MHz with a gain above 15 dB, and a high saturation power with quantum-limited noise performance. In addition, the center frequency of this device can be tuned over several hundred megahertz, which in turn broadens the effective operational bandwidth to around 1 GHz.

Vacuum-gap-based lumped element Josephson parametric amplifier

“…While R t meanly determines expansion of the spectral bandwidth, mismatch of iZ aux ω s /ω aux and standing wave emerged in the cable, produce ripple on the reflected spectrum. According to transmission line theory, [26,27] the total auxiliary CPW transformer (seen from the lumped part) has impedance of For the optimal pump power at certain pump frequency, the gain response spectral can be approximately given [25,27] as…”

“…On the fabrication aspect, TWPAs need reliable fabrication for series of thousands of Josephson junctions, and LJPAs are composed by superconducting quantum interference device (SQUID) and lumped capacitor, like interdigitated capacitor, [22] and parallel-plate capacitor. [23][24][25] It is worth noting that, to preserve working region, capacitors with small parasitic inductance, such as parallel-plate capacitor and vacuum-gap-based capacitor, are preferred. While parallelplate capacitor lowers parasitic inductance of the interdigitated capacitor, its multi-layer structure introduces fabrication complexity and amorphous heterogeneous interface, where surface defects are most likely to be found.…”

Synthesis of parametrically-coupled networks

“…The basic design has been recently reproduced in Refs. [55,56] albeit with small modifications. Despite its approachability, the design parameters were derived using a physics approach, and modifications to the gain, bandwidth and center frequency are less straightforward to produce [55].…”

Wideband Josephson Parametric Amplifier with Integrated Transmission Line Transformer

“…In this case the shape of the gain profile is in general not Lorentzian and the device gainbandwidth product ceases to be a constant, being limited only by the Bode-Fano theorem. Previously demonstrated impedance matched parametric amplifier used long tapers [18], [19], [21], [22] and complex reactive networks, resulting in a large device area. In this work we describe an on-chip wideband Josephson parametric amplifier that uses a transmission line impedance transformer [23], [24] to widen the amplifier instantaneous bandwidth of the JPA and increase saturation power without sacrificing chip area.…”