Travelling wave parametric amplifier isolator simplifies quantum readout chains

GRENOBLE, France - Nov. 14, 2025 - PRLog -- A collaborative team from Institut Néel (University Grenoble Alpes CNRS Grenoble INP), Silent Waves, with partners from Karlsruhe Institute of Technology and the University of Strasbourg has demonstrated a new superconducting travelling wave parametric amplifier with built in isolation. The result is published today in Nature Electronics under the title "A travelling wave parametric amplifier isolator" (DOI: 10.1038/s41928-025-01489-w).

Travelling wave parametric amplifiers are essential for high fidelity microwave readout in superconducting quantum systems. They provide high gain and near quantum limited noise over gigahertz bandwidths but normally require separate cryogenic isolators to prevent backward travelling radiation from reaching the device under test. These isolators take up valuable space in dilution refrigerators and reduce overall efficiency.

The newly reported travelling wave parametric amplifier isolator (TWPAI) provides amplification and isolation in a single Josephson junction based transmission line. Using engineered second and third order nonlinearities in a SNAIL based metamaterial, the device delivers up to 20 dB of forward gain, 30 dB of reverse isolation, and maintains near quantum limited added noise across a static 3 dB bandwidth greater than 500 MHz.

By embedding isolation directly into the amplifier, the TWPAI offers a clear route toward quantum readout linesthat do not rely on bulky cryogenic isolators. This supports the development of more compact and efficient architectures for scaling quantum processors and sensitive measurement platforms.

The work was led by Arpit Ranadive with co authors at Institut Néel, KIT/University of Strasbourg and supervised by Dr Nicolas Roch, who is also one of the founders of Silent Waves.

Nicolas Roch said:

"By integrating isolation directly into the amplifier we remove one of the main obstacles to compact high fidelity quantum readout chains and move closer to practical large-scale quantum processors."

The paper is available at:

https://www.nature.com/articles/s41928-025-01489-w

About Institut Néel

Institut Néel is one of the largest CNRS research laboratories working in condensed matter physics, quantum electronics, nanoscience and superconducting device fabrication. Based in Grenoble, it brings together leading teams and advanced cleanroom facilities and plays a central role in the European quantum technology ecosystem.

About Karlsruhe Institute of Technology

Karlsruhe Institute of Technology is a major German institution for science and engineering. KIT combines university research with large scale facilities and carries out internationally recognised work in quantum systems, superconducting circuits and condensed matter theory.

About Silent Waves

Silent Waves is a deeptech company based in Grenoble and founded by Luca Planat Nicolas Roch and Baptiste Planat. It is a spin off from Institut Néel and focuses on advancing readout performance for quantum computing, radio astronomy and electron spin resonance through ultra low noise amplification and expert technical support.