Magnetic Field-Resilient Quantum-Limited Parametric Amplifier

Abstract

Superconducting parametric amplifiers are crucial components in microwave quantum circuits for enabling quantum-limited signal readout. The best-performing such amplifiers are often based on Josephson junctions, which however are sensitive to magnetic fields. Therefore, they require magnetic shields and are not easily integratable with other quantum systems that operate within magnetic fields, such as spin-ensemble quantum memories. To tackle this challenge, we develop a kinetic inductance-based parametric amplifier featuring a NbN nanobridge instead of Josephson junctions, which provides the desired nonlinearity for a strong parametric gain up to 42 dB. The added noise of this nanobridge kinetic-inductance parametric amplifier (hereby referred to as NKPA) is calibrated and found to be 0.59±0.03 quanta for phase-preserving amplification, approaching the quantum limit of 0.5 quanta. Most importantly, we show that such excellent noise performance is preserved in an in-plane magnetic field up to 427 mT, the maximum field available in our experiment. This magnetic-field-resilient parametric amplifier presents an opportunity towards addressing single electron-spin resonance and more efficient search for axions as well as Majorana fermions.