Josephson squelch filter for quantum nanocircuits

TL;DR

This paper introduces a Josephson squelch filter that effectively suppresses small signals while allowing larger signals, enhancing low-temperature quantum nanocircuit measurements with high ON/OFF ratios up to 50 MHz.

Contribution

The paper presents a novel Josephson-based squelch circuit integrated with a copper powder filter, demonstrating high attenuation for small signals and normal filtering for large signals.

Findings

Attenuation exceeds 50dB up to 50 MHz

Effective suppression of small signals in quantum circuits

Compatible with low-temperature quantum measurements

Abstract

We fabricated and tested a squelch circuit consisting of a copper powder filter with an embedded Josephson junction connected to ground. For small signals (squelch-ON), the small junction inductance attenuates strongly from DC to at least 1 GHz, while for higher frequencies dissipation in the copper powder increases the attenuation exponentially with frequency. For large signals (squelch-OFF) the circuit behaves as a regular metal powder filter. The measured ON/OFF ratio is larger than 50dB up to 50 MHz. This squelch can be applied in low temperature measurement and control circuitry for quantum nanostructures such as superconducting qubits and quantum dots.