Floquet-Mode Traveling-Wave Parametric Amplifiers

Abstract

Simultaneous ideal quantum measurements of multiple single-photon-level signals would advance applications in quantum information processing, metrology, and astronomy but require the first amplifier to be simultaneously broadband, quantum limited, and directional. However, conventional traveling-wave parametric amplifiers support broadband amplification at the cost of increased added noise and are not genuinely directional due to non-negligible nonlinear backward-wave generation. In this work, we introduce a new class of amplifiers that encode the information in the Floquet modes of the system. Such Floquetmode amplifiers prevent information leakage and overcome the trade-off between quantum efficiency (QE) and bandwidth. Crucially, Floquet-mode amplifiers strongly suppress the nonlinear forward-backward wave coupling and are therefore genuinely directional and readily integrable with qubits, clearing another major obstacle toward broadband ideal quantum measurements. Furthermore, Floquet-mode amplifiers are insensitive to out-of-band impedance mismatch, which otherwise may lead to gain ripples, parametric oscillations, and instability in conventional traveling-wave parametric amplifiers. Finally, we show that a Floquet-mode Josephson traveling-wave parametric amplifier implementation can simultaneously achieve > 20 dB gain and a QE of η/η ideal > 99.9% of the quantum limit over more than an octave of bandwidth. The proposed Floquet scheme is also widely applicable to other platforms, such as kinetic inductance traveling-wave amplifiers and optical parametric amplifiers.

Broadband Continuous-Variable Entanglement Generation Using a Kerr-Free Josephson Metamaterial

“…In practice, the quantum efficiency and output field squeezing are also limited by the Kerr-type nonlinearity [41]. Besides that, the generation of higher-order harmonics products, increasing the losses in the TWPA [42], could lead to substantial degradation of the entanglement and squeezing performance.…”

X-parameter based design and simulation of Josephson traveling-wave parametric amplifiers for quantum computing applications

“…To this end, the past decade has seen a rapid development of parametric amplifier technology used to pre-amplify the fewphoton level (e.g.−150 dBm) readout signals used to probe readout resonators operating at 10 mK to determine the qubit states [11]. Josephson parametric amplifiers (JPAs) [2], [12]- [14] and traveling-wave parametric amplifiers utilizing either nonlinear kinetic inductance [15]- [17] or Josephson nonlinearity [3], [18]- [22] have achieved near-quantum limited noise performance and are now routinely used in superconducting circuit experiments and quantum sensing. JPAs have near-ideal intrinsic quantum efficiency and often consist of one or a few nonlinear resonators.…”

“…Josephson traveling wave parametric amplifiers (JTWPAs) are attractive components given their broad bandwidth (e.g. 3 GHz), high gain (20 dB), high saturation power (−100 dBm), and noise performance approaching the fundamental limit allowed by quantum mechanics [3], [18], [20], [22]. However, despite the suitable characteristics for qubit readout applications, JTWPAs typically consist of thousands of Josephson junctions and thus exhibit more complicated dynamics than JPAs.…”

“…The design and simulation of JTWPAs with desired performance still constitute a practical bottleneck for many quantum engineers. While simple, analytical two-mode wave-equation models [18], [30]- [32] are commonly used for device design and modeling, they fall short in predicting realistic multi-mode gain dynamics [33] and quantum efficiency [3], [22] and in capturing non-ideal behaviors observed in experiments, such as the cutoff frequency and photonic bandgaps that originate from the lumped-element nature of the JTWPA design [20], as well as parameter variability associated with fabrication uncertainties [34]- [37]. A harmonic balance method analysis of the signal gain in kinetic inductance traveling-wave parametric amplifiers was performed in [38]; however, for quantum efficiency calculations, the full Xparameter sensitivity matrix must be calculated including for inputs at all of the idler frequencies generated in the parametric processes.…”

Readout of a quantum processor with high dynamic range Josephson parametric amplifiers

“…High dynamic range JPAs using SQUID arrays have been demonstrated 12,13 , but while improving the input saturation power up to −95 dBm, they still suffer from relatively nara) Electronic mail: tcwhite@google.com b) Electronic mail: ofernaaman@google.com row bandwidths, less than 200 MHz. Traveling wave parametric amplifiers (TWPA) can provide bandwidths in excess of 2 GHz and high saturation power [14][15][16][17][18] , but are difficult to fabricate and typically have lower quantum efficiency than JPAs due to higher dissipative and intermodulation losses 19 . Practical systems considerations, such as qubit frequency placement plan 20 , Purcell filter bandwidth 21 , and mixer IF bandwidth 7 , can additionally prevent the full utilization of the TWPAs multi-GHz bandwidth.…”