Qubits are the foundation of quantum computing, but remain highly vulnerable to cosmic rays, which can induce decoherence and correlated errors. To study and mitigate these effects, U.S. Department of Energy national laboratories perform controlled experiments that replicate cosmic-ray conditions and analyze their impact on quantum devices. This research provides crucial insights for designing robust qubit architectures and effective error-mitigation strategies.
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What Are Simulated Cosmic Rays and Why Do Qubits Care?
Qubits are the fundamental units of quantum information that encode and process data using quantum mechanical states such as superposition and entanglement.
They are extremely sensitive to their environment, as electromagnetic noise and ionizing radiation can perturb the delicate energy states that maintain quantum information. They are particularly vulnerable to cosmic rays, whose high-energy particles can deposit significant energy in device substrates and disrupt coherence.
Cosmic rays are high-energy particles emitted by distant astrophysical sources, spanning a wide energy spectrum that enables them to penetrate shielding and act as a persistent background that can disturb superconducting materials.
These rays can trigger sudden decoherence or induce errors that propagate across multiple qubits, reducing computational fidelity and system reliability. It is therefore necessary to study these effects systematically to understand their impact and develop strategies to protect quantum devices.
To achieve this, scientists use simulated cosmic rays, artificially generated high-energy particles that replicate the properties of natural cosmic radiation under controlled laboratory conditions.
Simulated cosmic rays allow researchers to reproduce particle interactions with precise control over type, energy, and flux, enabling experiments that are both repeatable and statistically meaningful. This controlled testing provides insights into how radiation induces errors in different qubit architectures and supports the development of effective mitigation strategies to enhance coherence, stability, and overall quantum system reliability.
How Do Cosmic Rays Affect Qubits?
Cosmic rays affect quantum computing platforms through architecture-specific physical processes.
In superconducting qubits, energy deposited in the substrate generates phonons and excitations that break Cooper pairs, producing quasiparticles that disrupt superconductivity and induce correlated errors across qubit arrays.
Trapped-ion systems can experience heating from radiation-induced substrate excitations, while semiconductor spin qubits can experience charge-state fluctuations from ionizing particles.
These mechanisms demonstrate that cosmic radiation poses a cross-platform challenge, particularly because it introduces correlated error modes that existing quantum error correction schemes struggle to address.1
Role of U.S. National Laboratories in Studying Cosmic Ray Effects on Qubits
U.S. national laboratories play a key role in advancing the understanding of cosmic radiation effects on quantum systems. They provide specialized facilities and expertise for simulating high-energy particle interactions, collecting precise experimental data, and developing methodologies for evaluating qubit performance under radiation.
Los Alamos Neutron Science Center (LANSCE)
LANSCE operates a high-power linear accelerator that delivers proton beams up to 800 MeV, which are directed onto converter targets to produce high fluxes of secondary neutrons with spectra similar to those from atmospheric cosmic-ray interactions. This allows accelerated testing of radiation sensitivity in advanced electronic and quantum devices under energy and intensity conditions that can be systematically varied.
The principal techniques include proton beam acceleration, neutron field generation, and controlled irradiation of test assemblies, supported by instrumentation that records correlated error modes and threshold responses across device architectures.2
Johns Hopkins Applied Physics Laboratory (APL)
The Johns Hopkins Applied Physics Laboratory, in collaboration with the US DOE, is using its linear accelerator to generate controlled radiation that mimics the effects of cosmic-ray muons on superconducting qubits.
By driving electrons to energies that reproduce these high-energy interactions, researchers can trigger qubit-disrupting events on demand at cryogenic temperatures, eliminating the need to wait for naturally occurring cosmic rays. The platform also recreates terrestrial gamma-ray backgrounds, allowing comprehensive radiation-response testing with precise control over particle energy and flux.
This capability accelerates experiments from days to minutes while enabling systematic evaluation of qubit vulnerability and mitigation strategies.3
National Institute of Standards and Technology (NIST)
NIST employs precision laboratory setups rather than solely relying on high-energy accelerators. Its approach integrates controlled cryogenic environments with naturally occurring cosmic-ray and gamma-ray backgrounds to study how ionizing radiation deposits energy in the materials used in superconducting quantum processors.
The measurement platform includes cryogenic detectors, substrate calorimetry, and low-temperature radiation-sensing techniques to quantify energy deposition at millikelvin conditions. These methods replicate operational environments of quantum processors and provide calibration data that clarify how material properties and substrate geometries affect radiation-induced decoherence.4
Radiation Testing Techniques for Quantum Devices
Qubits are evaluated for radiation-induced effects using standard and fast T1 relaxation measurements, where standard T1 tracks average relaxation over long periods but cannot resolve rapid, millisecond-scale events caused by high-energy particle impacts.
To capture these fast dynamics, a sub-millisecond decay-detection protocol repeatedly prepares the qubit in its excited state, allows brief evolution, measures its state, and cools it before the next cycle. This protocol enables precise detection of sudden relaxation events caused by radiation, which would otherwise be obscured in standard measurements. By analyzing the resulting sequences of excited and ground states, researchers can distinguish true radiation-induced errors from spontaneous decay or noise, providing quantitative insights into qubit susceptibility and guiding the development of mitigation strategies.
Statistical analysis of these measurements, often combined with Monte Carlo simulations and controlled radioactive sources, allows researchers to quantify event rates and characterize the impact of different radiation types on qubit performance, supporting the design of more resilient qubits and the optimization of error-correction protocols to handle radiation-induced faults.5
Superconducting qubit chips are specifically engineered with SQUIDs for frequency tunability and distributed capacitor pads across multiple chips. Quasiparticle bursts are generated by driving selected qubits with resonant microwave pulses, producing excitations that propagate through the substrate, break Cooper pairs, and induce correlated charge-parity jumps and bit-flip errors. These events are monitored across multiple qubits simultaneously, with data smoothing and statistical thresholds applied to distinguish genuine radiation-induced events from background noise.
In one study, a 63-qubit chip with 105 couplers was tested using this protocol, enabling controlled quasiparticle injections and reliable detection of bursts lasting tens of microseconds, with thresholds set at 6–6.6σ over acquisition times from approximately 600 seconds to over 22,000 seconds, providing quantitative characterization of qubit relaxation and susceptibility to quasiparticle-induced errors.6
Overall, these methods enable fast, high-resolution, and reproducible detection of transient qubit relaxation events and controlled quasiparticle-induced errors, providing quantitative insights into decoherence mechanisms that would otherwise require extensive time to observe with conventional measurements.
What Have We Learned About Qubits Under Radiation?
Radiation can significantly degrade superconducting qubit performance by breaking Cooper pairs and generating quasiparticles that induce decoherence. This was demonstrated by researchers at PNNL and MIT, who conducted controlled experiments in which qubits were exposed to different radiation levels and shielding conditions.
The results revealed a clear inverse relationship between radiation exposure and qubit coherence, emphasizing the need for careful material selection, effective shielding, or operation in low-radiation environments to maintain reliable quantum performance. These effects also extend to other superconducting devices, such as dark matter detectors, highlighting radiation as a critical factor in device reliability once fabrication and material limitations are addressed.7
Additional research has shown that radiation can induce spatiotemporally correlated errors across multiple qubits, complicating error correction efforts. For example, a recent experiment monitored a ten-qubit array on a silicon chip while simultaneously measuring cosmic-ray flux with scintillating detectors, revealing that cosmic-ray impacts and secondary particle interactions accounted for roughly 17.1% ± 1.3% of all correlated relaxation events.
This highlights the significant role of cosmic radiation in generating multi-qubit error patterns and underscores the need for strategies to mitigate correlated failures in scalable quantum systems.8
Implications for Fault-Tolerant Quantum Computing
Understanding radiation effects in superconducting qubits informs both quantum error correction and hardware design.
Studies showing that cosmic rays can induce spatiotemporally correlated errors highlight limitations in conventional error-correction codes that assume independent faults. This knowledge enables optimized code selection, adjusted hardware layouts, and tailored error thresholds, allowing protocols to manage correlated radiation-induced events and improve overall fault tolerance in quantum systems.
At the hardware level, insights into quasiparticle generation and decoherence guide radiation-hardened qubit design through superconducting gap optimization, phonon and quasiparticle trapping, engineered material layering, and layouts that minimize correlated errors. When integrated with adaptive error-correction protocols, these strategies enhance coherence, stability, and fault tolerance.
Such approaches are critical for commercial quantum computing roadmaps, enabling scalable processors such as Google’s Willow and IBM’s 200-logical-qubit systems to maintain error thresholds and reliable operation in radiation-prone environments.9
What’s Next in Qubit Radiation Research
Next-generation experiments will evaluate emerging mitigation strategies, including low-radioactivity substrates, alternative superconducting alloys, and engineered dielectric layers, using accelerator facilities to enable rapid, controlled testing.
However, challenges remain in fully characterizing correlated, multi-qubit radiation events and scaling mitigation techniques to large arrays.
These issues can be addressed by integrating high-fidelity simulations with adaptive testing protocols, combining hardware-level protections with advanced error-correction schemes, and fostering collaborative efforts across research institutions and industry to accelerate development of robust, fault-tolerant quantum processors capable of operating reliably in radiation-prone environments.
Discover the history of cosmic ray research here
References and Further Reading
- Wilen, C. D., Abdullah, S., Kurinsky, N. A., Stanford, C., Cardani, L., Tomei, C., Faoro, L., Ioffe, L. B., Liu, C. H., Opremcak, A., Christensen, B. G., DuBois, J. L., & McDermott, R. (2021). Correlated charge noise and relaxation errors in superconducting qubits. Nature, 594(7863), 369-373. https://doi.org/10.1038/s41586-021-03557-5
- LANSCE. (2025). LINAC. https://lansce.lanl.gov/facilities/linac.php
- Raj, A. (2025). Accelerating Qubit Testing With Cosmic Rays on Demand. https://www.jhuapl.edu/news/news-releases/250424-linac-qubit-testing
- Fowler, J. W., Szypryt, P., Bunker, R., Edwards, E. R., Florang, I. F., Gao, J., Giachero, A., Hoogerheide, S. F., Loer, B., Mumm, H. P., Nakamura, N., O’Neil, G. C., Orrell, J. L., Scott, E. M., Stevens, J., Swetz, D. S., VanDevender, B. A., Vissers, M., & Ullom, J. N. (2024). Spectroscopic Measurements and Models of Energy Deposition in the Substrate of Quantum Circuits by Natural Ionizing Radiation. PRX Quantum, 5(4). https://doi.org/10.1103/prxquantum.5.040323
- Roy, T., De Dominicis, F., Mariani, A., Bal, M., Casali, N., Colantoni, I., ... & Cardani, L. (2024). Evaluating Radiation Impact on Transmon Qubits in Above and Underground Facilities (No. FERMILAB-SLIDES-24-0118-SQMS). Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States). https://arxiv.org/html/2405.18355v2
- Li, X., Wang, J., Jiang, Y., Xue, G., Cai, X., Zhou, J., Gong, M., Liu, Z., Zheng, S., Ma, D., Chen, M., Sun, W., Yang, S., Yan, F., Jin, Y., Zhao, S. P., Ding, X., & Yu, H. (2025). Cosmic-ray-induced correlated errors in superconducting qubit array. Nature Communications, 16(1), 4677. https://doi.org/10.1038/s41467-025-59778-z
- Vepsäläinen, A. P., Karamlou, A. H., Orrell, J. L., Dogra, A. S., Loer, B., Vasconcelos, F., Kim, D. K., Melville, A. J., Niedzielski, B. M., Yoder, J. L., Gustavsson, S., Formaggio, J. A., VanDevender, B. A., & Oliver, W. D. (2020). Impact of ionizing radiation on superconducting qubit coherence. Nature, 584(7822), 551-556. https://doi.org/10.1038/s41586-020-2619-8
- Harrington, P. M., Li, M., Hays, M., Mayer, D., Pinckney, H. D., Contipelli, F., Gingras, M., Niedzielski, B. M., Stickler, H., Yoder, J. L., Schwartz, M. E., Grover, J. A., Serniak, K., Oliver, W. D., & Formaggio, J. A. (2025). Synchronous detection of cosmic rays and correlated errors in superconducting qubit arrays. Nature Communications, 16(1), 6428. https://doi.org/10.1038/s41467-025-61385-x
- Choi, C. Q. (2022, December 7). Cosmic Rays Are Quantum Computers’ Kryptonite. IEEE Spectrum. https://spectrum.ieee.org/quantum-computing-cosmic-rays
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