Summary:
UCLA researchers led by Professor Pri Narang have developed a fully superconducting, on-chip readout architecture that improves signal fidelity and limits backpropagation in quantum processors
Background:
Superconducting quantum processors can perform complex calculations orders of magnitude quicker than classical computers. Current superconducting quantum processors rely on dispersive readouts to measure a superconducting qubit’s state. To ensure high-fidelity measurement, traditional systems utilize ferrite-based components that limit the scalability of superconducting quantum computers. While ferrite components are necessary to block noise, they come with significant drawbacks in scalability and signal quality. These components are bulky, occupying space in the chandelier and severely limiting the density of signal lines. In addition, ferrites introduce insertion loss, significantly degrading the signal-to-noise ratio and reducing signal fidelity. Ferrite-based components require strong magnetic fields that may be harmful to hardware, necessitating complex shielding to protect superconducting qubits. To overcome these limitations and improve quantum signal fidelity, there is a need for a readout solution that is compact, lossless, and fully integrated on-chip.
Innovation:
Researchers at UCLA have developed a passive, on-chip superconducting diode readout chain. The readout chain contains a superconducting qubit, a dispersive readout resonator, and a superconducting diode placed before the cryogenic amplifier. The architecture enforces unidirectional signal flow by maximizing forward transmission while blocking reverse path noise to prevent signal backpropagation. The device exhibits a forward-to-reverse transmission of over 20dB at the readout frequency, matching isolation levels of commercial ferrite circulators at a fraction of the insertion loss. This ensures high-fidelity readout by maintaining a high signal-to-noise ratio. Additionally, this invention offers flexible implementation, utilizing either Josephson diodes or bulk superconductor configurations, enabling a scalable fabrication process compatible with existing superconducting foundry capabilities. In conclusion, this novel architecture resolves critical bottlenecks in existing quantum computing solutions, paving the way for the next generation of high-fidelity superconducting quantum processors.
Potential Applications:
● Superconducting Quantum Processors
● Qubit Measurement
● Cryogenic Sensor Arrays
● Integrated Quantum Circuitry
Advantages:
● Scalable
○ Compatible with standard foundries
● Compact
● No Magnetic Interference
● Enhanced Readout Fidelity
○ Improved signal-to-noise ratio
● Passive
Development-To-Date:
First description of the complete invention.
Related Papers:
Dirnegger, Nicolas, et al. "Nonreciprocal Quantum Information Processing with Superconducting Diodes in Circuit Quantum Electrodynamics." arXiv, 25 Nov. 2025, https://doi.org/10.48550/arXiv.2511.20758
Reference:
UCLA Case No. 2026-079
Lead Inventor:
Professor Prineha Narang