Impact of ionizing radiation on superconducting qubit coherence

Technical Report · Wed Apr 01 00:00:00 EDT 2020

DOI:https://doi.org/10.2172/1602215· OSTI ID:1602215

Vepsalainen, Annti P. ^[1]; Karamlou, Amir H. ^[1]; Orrell, John L. ^[2]; Dogra, Akshunna S. ^[3]; Loer, Ben ^[2]; Vasconcelos, Francisca ^[1]; Kim, David K. ^[4]; Melville, Alexander J. ^[4]; Niedzielski, Bethany M. ^[4]; Yoder, Jonilyn L. ^[4]; Gustavsson, Simon ^[1]; Formaggio, Joseph A. ^[1]; VanDevender, Brent A. ^[2]; Oliver, William D. ^[5]

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1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
3. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Harvard Univ., Cambridge, MA (United States)
4. Massachusetts Inst. of Technology (MIT), Lexington, MA (United States)
5. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Massachusetts Inst. of Technology (MIT), Lexington, MA (United States)

The practical viability of any qubit technology stands on long coherence times and high-fidelity operations, with the superconducting qubit modality being a leading example. However, superconducting qubit coherence is impacted by broken Cooper pairs, referred to as quasiparticles, with a density that is empirically observed to be orders of magnitude greater than the value predicted for thermal equilibrium by the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity. Previous work has shown that infrared photons significantly increase the quasiparticle density, yet even in the best isolated systems, it still remains higher than expected, suggesting that another generation mechanism exists. In this Letter, we provide evidence that ionizing radiation from environmental radioactive materials and cosmic rays contributes to this observed difference, leading to an elevated quasiparticle density that would ultimately limit superconducting qubits of the type measured here to coherence times in the millisecond regime. We further demonstrate that introducing radiation shielding reduces the flux of ionizing radiation and positively correlates with increased coherence time. Albeit a small effect for today’s qubits, reducing or otherwise mitigating the impact of ionizing radiation will be critical for realizing fault-tolerant superconducting quantum computers.

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP); US Army Research Office (ARO); National Science Foundation (NSF); Assistant Secretary of Defense for Research and Engineering
• DOE Contract Number: SC0019295; W911NF-14-1-0682; W911NF-18-1-0218; PHY-1720311; FA-8721-05-C-0002; AC05-76RL01830
• OSTI ID: 1602215
• Report Number(s): DOE-QIS-001; TRN: US2103855
• Resource Relation: Related Information: https://arxiv.org/abs/2001.09190
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
nuclear physics
quantum computing