A DC-powered Josephson isolator

Isolation is key to high-fidelity readouts of quantum signals at millikelvin temperatures, as it protects sensitive devices under study from noise and backaction of downstream amplification stages. The non ideal ferrite circulators commonly used at the dilution stage would ideally be replaced with more efficient and scalable on-chip counterparts behaving non-reciprocaly.

We propose a novel architecture of circuit comparable to Traveling Wave Parametric devices (Amplifiers, Converters) based on a voltage-biased pair of Josephson junctions. The isolation of input signal is realized with parametric frequency conversion that is made directional with tunable flux/delay interference. As the device is DC powered, this removes the need for routing and filtering out a cumbersome strong microwave pump tone near the chip, though it comes at the cost of complex engineering of the linear part of the circuit.

In this talk we will present the semiclassical approach used to model and simulate the circuit, along with experimental results of recently measured devices.