Magnetic field-resilient quantum-limited parametric amplifier

Superconducting quantum-limited parametric amplifiers (QPA), ideal for linear detection of weak signals, have become indispensable components for microwave quantum systems. The state-of-art QPA's exploit the strong nonlinearity of a Josephson junction. However, the junction based QPA is sensitive to magnetic fields, neccessating the use of a magnetic shield in operation. Therefore they are incompatible with quantum systems that operate with magnetic fields. In this work, we present a quantum-limited amplifier made from NbN thin films. The nonlinearity originates from the kinetic inductance of the NbN nanobridge. We show that when operated in either phase-sensitive or phase-preserving mode, the added noise of our amplifier approaches the quantum limit.