Superconducting SQUID Response Characterised to Neutron and Gamma Radiation Sources

Superconducting quantum devices represent a transformative technology with potential applications ranging from medical imaging to advanced computation, but their sensitivity to external radiation poses a significant challenge to reliable operation. Gioele Casagranda, Elizabeth Auden, and Carlo Cazzaniga, along with colleagues at various institutions, investigate how different types of radiation impact the performance of a superconducting quantum interference device, known as a SQUID. The team exposed the SQUID to beams of neutrons, both mono-energetic and those mimicking atmospheric conditions, and gamma rays, revealing a surprising vulnerability to neutron radiation while demonstrating resilience to gamma rays at the tested energy levels. This research not only characterises the SQUID’s response to these radiation sources, allowing for the classification of faults based on their characteristics, but also provides crucial insights into protecting these delicate devices from environmental interference and improving their long-term stability.

Conducting technology currently focuses scientific research and drives industrial applications, excelling in both performance and scalability. Despite these advances, superconducting quantum systems remain extremely prone to decoherence and exhibit high sensitivity to radiation events. This paper analyses the response of a Superconducting Quantum Interference Device, or SQUID, to various forms of radiation. The SQUID was exposed to beams of monoenergetic 1 MeV neutrons from the NILE facility at ISIS, atmospheric 1 MeV neutrons from the ChipIR facility at ISIS, and gamma rays with a 1 MeV average energy from the CALLIOPE facility at ENEA. These experiments demonstrate that the SQUID exhibits sensitivity to both neutron fields, while gamma rays at 1 MeV leave it largely unaffected

Radiation Effects on Superconducting Qubits

Research into superconducting qubits explores how external radiation impacts their performance, a crucial step towards building reliable quantum technologies. Investigations cover a broad range of radiation sources, including cosmic rays, natural radioactivity, gamma rays, and neutrons. The primary effects investigated include quasiparticle poisoning, where radiation creates excitations that disrupt qubit coherence, material damage, and changes in dielectric properties. Researchers are exploring mitigation strategies such as shielding, locating qubits underground, careful material selection, and designing qubits less susceptible to radiation.

Studies utilize various characterization techniques to measure radiation levels and their effects on qubits, alongside computational simulations to predict radiation effects and optimize mitigation strategies. Researchers are characterizing neutron generators and gamma irradiation facilities to better understand the radiation environment. This work builds on existing knowledge of qubit technology and provides a foundation for future advancements. The research highlights the importance of quasiparticle poisoning as a major concern, with the GEANT4 toolkit frequently used for simulating radiation interactions.

Locating qubits underground offers protection from cosmic rays, and careful material selection is essential for minimizing radiation damage. Active irradiation studies, using dedicated gamma and neutron sources, are becoming increasingly common. Modeling and simulation are crucial for understanding complex radiation interactions and optimizing mitigation strategies. Potential research directions include developing advanced shielding materials, designing radiation-hardened qubits, creating real-time radiation monitoring systems, and developing error correction strategies robust to radiation-induced errors. Improving simulation models and characterizing a wider range of materials used in qubit fabrication are also important areas of focus. Combining different mitigation strategies, such as shielding, material selection, and qubit design, may prove particularly effective.

SQUIDs Show Neutron Radiation Sensitivity

Superconducting quantum devices promise advancements in fields like medical imaging and computing, owing to their exceptional sensitivity and scalability. However, a significant challenge hindering their widespread adoption is their vulnerability to decoherence, particularly from external radiation. Recent research has focused on understanding how these devices, specifically Superconducting Quantum Interference Devices (SQUIDs), respond to different types of radiation, paving the way for improved reliability and performance. The investigation involved exposing SQUIDs to beams of neutrons and gamma rays, simulating conditions relevant to various operating environments.

Results demonstrate that SQUIDs are sensitive to neutron radiation, while remaining largely unaffected by the tested levels of gamma radiation. This distinction is crucial, as it suggests that neutron exposure represents a primary threat to device operation and longevity. Researchers were able to identify two distinct responses to neutron impacts: short-lived “peaks” and longer-lasting “bursts”, offering insights into the nature of radiation-induced faults. Detailed simulations, employing software like Geant4, corroborated these experimental findings, highlighting differences in how energy is deposited and propagates within the SQUID under neutron and gamma ray exposure.

These simulations confirmed the vulnerability of the device to both radiation types, but also provided a deeper understanding of the underlying physical mechanisms. The ability to characterize the SQUID’s response and classify faults based on their duration represents a significant step towards developing mitigation strategies. This research addresses a critical gap in the systematic study of superconducting quantum devices, offering fundamental insights into their behavior under radiation. While current solutions to radiation interference often rely on cumbersome shielding, a thorough understanding of the underlying mechanisms will enable the development of more targeted and scalable solutions, ultimately accelerating the progress of this transformative technology. The findings underscore the importance of addressing the reliability issue to unlock the full potential of superconducting quantum devices and facilitate their integration into real-world applications

SQUIDs Detect Neutrons, Altered by Gamma Rays

The research demonstrates that Superconducting Quantum Interference Devices (SQUIDs) are sensitive to neutron radiation, exhibiting distinct responses that can be categorized as either bursts or peaks, potentially linked to the type of incident particle. Experiments using neutron beams of varying energies confirmed this sensitivity and established the feasibility of testing quantum technologies within existing facilities. While the SQUID proved largely unaffected by the tested gamma ray energies, subsequent measurements revealed a significant increase in the device’s sensitivity to all external stimuli, suggesting potential, yet unidentified, consequences from gamma ray exposure. The authors acknowledge limitations stemming from the experimental setup, particularly concerning signal transmission and potential energy losses in one of the gamma ray experiments. They propose improvements such as a signal amplifier and a higher-performance cooling system to reduce thermal noise and enhance the detection of subtle changes. Future work will focus on implementing these enhancements and utilizing a cryostat designed for irradiation studies to further minimize noise and improve measurement precision, ultimately enabling more sensitive and reliable testing of superconducting quantum devices.