Pilipenko, Roman M. | Search NASA

DOE OSTI2026

Optimized cryogenic setup for microwave loss characterization of superconducting coaxial cables

As superconducting quantum systems scale up to enable applications like large-scale quantum computing, challenges such as fabrication yield, wiring complexity, and microwave crosstalk drive the need for high-fidelity, low-loss, modular interconnects. In recent experiments, the performance of these interconnects is often limited by cable loss, a factor that becomes even more critical as we aim for higher fidelity operations and connect increasingly coherent modules. In this talk, we present our cryogenic microwave loss characterization setup, carefully designed to minimize losses external to the coaxial cables under test. We also share results for several commercially-available superconducting cables measured with this setup and briefly discuss our ongoing efforts to develop custom coaxial cables capable of achieving state-of-the-art performance.

Vallières, André [Northwestern U.]↗

DOE OSTI2026

Optimized cryogenic setup for microwave loss characterization of superconducting coaxial cables

As superconducting quantum systems scale up to enable applications like large-scale quantum computing, challenges such as fabrication yield, wiring complexity, and microwave crosstalk drive the need for high-fidelity, low-loss, modular interconnects. In recent experiments, the performance of these interconnects is often limited by cable loss, a factor that becomes even more critical as we aim for higher fidelity operations and connect increasingly coherent modules. In this talk, we present our cryogenic microwave loss characterization setup, carefully designed to minimize losses external to the coaxial cables under test. We also share results for several commercially-available superconducting cables measured with this setup and briefly discuss our ongoing efforts to develop custom coaxial cables capable of achieving state-of-the-art performance.

Vallières, André [Northwestern U.]↗

DOE OSTI2024

Progress on 3D SRF-based architecture for quantum computing

Superconducting radio frequency (SRF) cavities are excellent choices for storing and manipulating quantum information as quantum d-level systems (qudits) due to their exceptionally long lifetimes and large accessible Hilbert spaces. A common strategy to manipulate the states is to use a nonlinear element like a transmon. We present preliminary experimental results obtained with cavity displacements and selective number dependent arbitrary phase gates for universal qudit control, and its application towards High-energy physics (HEP) simulations and beyond. We discuss the advantages and challenges associated with building a 3D SRF architecture while maintaining long cavity lifetimes in the presence of lossy components. We show how the system coherence properties can be preserved by carefully engineering to minimize the participation of the long coherence modes in different loss channels, while ensuring sufficient quantum controllability. We further discuss the path towards building multi-qudit systems.

Romanenko, Alexander↗

DOE OSTI2024

Quantum communications work at SQMS

The Superconducting Quantum Materials and Systems (SQMS) Center is focused on advancing low-loss interconnectivity between quantum processing units (QPUs) to enable scalable quantum computing. In the short term, our goals include the development and optimization of 2D and 3D platforms with remotely entangled modules, refinement in microwave design and control schemes, and the achievement of high-fidelity quantum state transfer between superconducting quantum modules. Looking ahead, we aim to realize modular quantum computing with low-loss interconnects, maximize remote entanglement fidelity and implement robust quantum operations with error correction. We will leverage advanced microwave engineering and material science to optimize the performance of quantum interconnects and the coupling interfaces between the interconnects and the QPUs.

Vallières, André↗

DOE OSTI2024

Evaluating Radiation Impact on Transmon Qubits in Above and Underground Facilities

Superconducting qubits can be sensitive to abrupt energy deposits caused by cosmic rays and ambient radioactivity. Previous studies have focused on understanding possible correlated effects over time and distance due to cosmic rays. In this study, for the first time, we directly compare the response of a transmon qubit measured initially at the Fermilab SQMS above-ground facilities and then at the deep underground Gran Sasso Laboratory (INFN-LNGS, Italy). We observe same average qubit lifetime T$_1$ of roughly 80 microseconds at above and underground facilities. We then apply a fast decay detection protocol and investigate the time structure, sensitivity and relative rates of triggered events due to radiation versus intrinsic noise, comparing above and underground performance of several high-coherence qubits. Using gamma sources of variable activity we calibrate the response of the qubit to different levels of radiation in an environment with minimal background radiation. Results indicate that qubits respond to a strong gamma source and it is possible to detect particle impacts. However, when comparing above and underground results, we do not observe a difference in radiation induced-like events for these sapphire and niobium-based transmon qubits. We conclude that the majority of these events are not radiation related and to be attributed to other noise sources which by far dominate single qubit errors in modern transmon qubits.

Roy, Tanay↗