A fourteen-decibel improvement in averaged gain was achieved along with improved quantum-limited noise performance within a new superconducting circuit architecture. A Josephson voltage standard integrated to create a stable phase reference for Josephson Photonics devices. This approach coherently transfers that reference to an inelastic Cooper-pair tunneling amplifier via the superconducting order parameter and also represents the first observation of phase-sensitive gain and squeezing in a dc-biased amplifier.

An improved design for devices central to superconducting quantum technology created by addressing limitations in signal control. The integration of a Josephson voltage standard, a precise electrical reference, stabilises signals within an inelastic Cooper-pair tunneling amplifier; these amplifiers boost weak quantum signals without adding excessive noise. Superconducting quantum device design has advanced sharply by tackling challenges related to signal control because parametric interactions are essential building blocks like amplifiers and qubit entanglement but can suffer from unwanted noise.

Limitations inherent in conventional microwave-driven systems, which introduce disruptive effects akin to static on a radio receiver, addressed through the integration of a Josephson voltage standard, an exceptionally precise electrical reference. This new approach establishes a stable phase reference for devices utilising dc-biased junctions, notably an inelastic Cooper-pair tunneling amplifier functioning as a microscopic valve controlling electron pair flow to amplify weak signals with minimal disturbance. Achieving fourteen decibels improvement in gain alongside better noise performance represents a step forward; however, questions remain regarding scaling this technology towards more complex quantum circuits.

Stabilised amplification through direct current biasing enhances Josephson photonic performance

A fourteen decibel improvement in averaged gain alongside better quantum-limited noise performance represents an advancement in Josephson photonics devices. Previously, high phase noise limited amplification capabilities and prevented observation of key effects. This new approach circumvents limitations inherent in conventional microwave pumping methods which introduce unwanted nonlinearities impacting device stability, establishing a strong platform enabling higher purity parametric processes essential for advanced superconducting circuits.

Stabilising Quantum Signals Through Coherent Phase Transfer in Superconducting Amplifiers

These systems are akin to building an electronic circuit with incredibly sensitive switches responding to tiny electrical changes but require careful shielding from noise. The technique involved coherently transferring that established phase information directly into an inelastic Cooper-pair tunneling amplifier via the superconducting order parameter; this ICTA functions as a microscopic valve controlling electron flow and amplifying weak quantum signals.

A custom fabricated filter provided isolation between these components, reaching approximately 50 decibels on average and peaking at 65 decibels near 12 gigahertz where it stabilises the ICTA bias. Delivering a clean, consistent timing signal enabled both phase-sensitive gain and squeezing, effectively fine-tuning reception while minimising static within the dc-biased amplifier itself. Designed around a six-gigahertz resonant mode featuring adjustable gain controlled via a Superconducting Quantum Interference Device or SQUID, the ICTA had a bandwidth of roughly 1.2 gigahertz; this configuration allows for precise control over amplification characteristics.

Superconducting circuit stability enhanced, but scalability to large quantum processors requires further work

The integration of a Josephson voltage standard offers a pathway towards more stable superconducting circuits however limited insight into how readily this approach scales with increasing system complexity is provided. While initial demonstrations show impressive gains and reduced noise, practical implementation within larger quantum processors presents significant engineering hurdles not fully addressed in this study. Specifically, maintaining coherence as component counts rise, alongside associated signal integrity, remains an open question that could limit widespread adoption despite these promising results.

By coherently transferring a phase reference from the precise electrical source to an inelastic Cooper-pair tunneling amplifier via the superconducting order parameter, this integrated system delivers a stable foundation for manipulating quantum signals; effectively synchronising operations within the circuit. The resulting architecture overcomes limitations imposed by previous phase instability which restricted amplification and prevented observation of effects like squeezing where uncertainty is reduced in one property at the expense of another. Demonstrating both phase-sensitive gain and squeezing establishes new possibilities for high-purity parametric processes essential to advanced superconducting circuits.

The researchers demonstrated a 14-dB enhancement in averaged gain and improved noise performance using a Josephson voltage standard to stabilise an inelastic Cooper-pair tunnelling amplifier operating around 12 gigahertz. This integration provides a more stable platform for manipulating quantum signals, overcoming prior issues with phase instability that limited device functionality.

The system enabled first observations of phase-sensitive gain and squeezing within a dc-biased amplifier, establishing potential for higher purity parametric processes. Further work is needed to understand how this approach scales as systems become more complex; the study highlights challenges related to maintaining coherence with increasing component counts.

👉 More information
🗞 Phase-stable voltage bias for Josephson photonics devices
✍️ Amir Hosein Esmaeili, Naveen Nehra, Alexandre Paquette, Mona Arabmohammadi, Baptiste Monge, Alexandre Rogalle, Francois Cyrenne-Bergeron, Yannick Lapointe, Nicolas Lavoie, Nicolas Bourlet and Max Hofheinz
🧠 ArXiv: https://arxiv.org/abs/2609.17165

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