Quantum mechanics

Engineering

Bandwidth (computing)

Operational amplifier

Optical amplifier

Broadband

Telecommunications

Amplifier

Computer science

Floquet theory

Parametric oscillator

Laser

Physics

Nonlinear system

Optics

Current sense amplifier

PRX Quantum

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 Floquet-mode 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 >20dB gain and a QE of η/ηideal>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.5 MoreReceived 11 June 2021Revised 28 January 2022Accepted 3 March 2022DOI:https://doi.org/10.1103/PRXQuantum.3.020306Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasMetamaterialsQuantum information with solid state qubitsQuantum metrologySuperconducting quantum opticsPhysical SystemsSuperconducting devicesSuperconducting qubitsQuantum InformationAtomic, Molecular & Optical

Floquet-Mode Traveling-Wave Parametric Amplifiers