Magnetic-field and temperature dependence of a NbTiN kinetic-inductance TWPA

Kinetic-inductance travelling wave parametric amplifiers (KTWPAs) have demonstrated near-quantum-limited amplification at up to 4 GHz bandwidth, and at about 30 dB higher saturation power than the more established Josephson TWPAs (JTWPAS) [1]. KTWPAs have an edge in the magnetic-field compatibility, which is due to the higher critical field of the used materials and due to the absence of the Fraunhofer magnetic field dependence inherent to JTWPAs [2]. Here we show that a kinetic inductance TWPA, consisting of a NbTiN microstrip and a Nb ground plane, can provide at least 10 dB of SNR improvement up to in-plane fields of 0.6 T and out-of-plane fields of 0.05 T, improving the limits shown for JTWPAs by an order of magnitude. The limit of the field compatibility is imposed by the ground plane, and can be further improved by using a different material or by fabricating vortex traps. This shows that KTWPAs potentially have many applications that require high magnetic field at the sample, such as experiments on topological qubits or on the search for axionic dark matter. We also find that the SNR improvement provided by the KTWPA does not worsen when increasing the temperature up to 2 K. This shows that KTWPAs are also technologically relevant for experiments performed at higher temperatures, for example in astrophysics detectors or spin qubit setups. It also suggests that KTWPAs could be mounted at higher stages of a cryostat compared to JTWPAs, thus partially mitigating the issue of increased pump power.