Wireless Josephson Amplifier Boosts Quantum Readout at Millimeter-Wave Frequencies

The quest for more powerful and scalable quantum computing systems drives innovation in high-frequency signal amplification, and researchers are now pushing the boundaries of what’s possible. Z. Hao, J. Cochran, and Y. Chuang, all from the Chandra Department of Electrical and Computer Engineering at the University of Texas at Austin, along with their colleagues, have designed and demonstrated a novel wireless Josephson parametric amplifier capable of operating above 20 GHz. This achievement addresses a critical need for near-quantum-limited noise amplification at higher frequencies, which is essential for preserving the delicate quantum states used in these advanced systems. By eliminating the losses and impedance mismatches that plague traditional amplifiers at these frequencies, the team’s wireless design delivers over 20 dB of gain across a tunable range, exhibiting remarkably low added noise of approximately two photons and paving the way for more complex and powerful quantum technologies.

Wireless Josephson Amplifier Exceeds 20 GHz

This research details the development of a high-frequency (above 20 GHz) wireless Josephson parametric amplifier (JPA). This advancement is crucial for scaling up quantum computing systems, as higher operating frequencies allow for denser qubit control and readout. The researchers successfully designed and fabricated a JPA operating at frequencies significantly higher than those typically achieved with this technology, offering over 20 decibels of gain across a tunable range of 21 to 23. 5 GHz with a bandwidth of 3 MHz. Key features include a wireless design, optimized coupling structure, and low noise performance, exhibiting near-quantum-limited noise.

Higher operating frequencies enable denser integration of qubits on a chip, a critical step towards building larger and more powerful quantum computers, while also allowing for faster manipulation and measurement of qubit states. Wireless designs help to reduce the complexity and congestion of wiring in quantum circuits, simplifying fabrication and improving reliability. The amplifier utilizes Josephson junctions and a carefully designed resonator to enhance amplification.

High-Frequency, Low-Noise Wireless Josephson Amplification

This research demonstrates a new wireless Josephson parametric amplifier (WJPA) that operates above 20 GHz, representing the first such device to achieve this frequency. These results are significant because they address a key challenge in scaling superconducting qubit systems, namely the need for high-frequency amplification with minimal added noise to preserve qubit coherence and enable fast, high-fidelity readout. The authors note that future work could explore implementation with niobium-based Josephson elements, broadening the applicability of the amplifier to a wider range of superconducting qubit technologies. The data supporting this research are openly available, facilitating further investigation and development in the field of quantum information processing.