Full Kerr Cancellation in an Inductively-Shunted Josephson Ring Modulator*

Quantum-limited amplification plays a vital role in efficient quantum measurement. For superconducting qubits, such amplification can be achieved through parametrically driven three-wave mixing in the Josephson Ring Modulator (JRM). However, we have shown that Kerr nonlinearities in and between the JRM’s modes limit the device’s saturation power and jeopardize frequency matching conditions for multiply parametric driven modes of operation. We present a JRM shunted with linear inductors [1] which, for a range of parameters, cancels all the Kerr terms at a certain flux bias point while retaining three-wave mixing terms. The stability of this special bias point depends crucially on the ratio of shunt inductance to Josephson junction inductance as well as stray inductance in the JRM ring itself. We present both self- and cross-Kerr measurements showing simultaneous cancellation as well as the absence of fourth-order behaviors in the amplifier’s response to large signal powers. This device, in addition to enhanced saturation power is expected to be an excellent candidate for multiply-driven parametric devices.
[1] N. Roch et al, PRL 108, 147701 (2012)