Synchronous detection of cosmic rays and correlated errors in superconducting qubit arrays

Area of Science:

• Quantum Computing
• Quantum Error Correction
• Superconducting Qubits

Background:

• Scalable quantum information processing relies on stable, long-lived qubits, often necessitating quantum error correction codes.
• Recent superconducting qubit experiments show problematic spatiotemporally correlated errors, likely caused by ionizing radiation.
• Conventional quantum error correction codes struggle with these intermittent, correlated errors.

Purpose of the Study:

• To directly measure the contribution of cosmic rays to spatiotemporally correlated errors in superconducting qubits.
• To investigate the relationship between cosmic ray flux and qubit error events.
• To explore methods for mitigating cosmic ray-induced errors in quantum systems.

Main Methods:

• Synchronous monitoring of cosmic ray detectors and the energy relaxation dynamics of 10 transmon qubits.
• Distribution of qubits across a 5 × 5 × 0.35 mm³ silicon chip for comprehensive measurement.
• Analysis of qubit responses to incident cosmic rays and their secondary particles.

Main Results:

• Cosmic rays induce correlated qubit errors at a rate of 1/(592 ± 41) s, accounting for 17.1 ± 1.3% of all such events.
• Qubits demonstrated high sensitivity, responding to nearly all incident cosmic rays and secondary particles.
• The superconducting gap's landscape near Josephson junctions significantly influences qubit susceptibility to cosmic rays.

Conclusions:

• Cosmic rays are a significant source of correlated errors in superconducting qubits.
• Radiation hardening, particularly through superconducting gap engineering, is vital for achieving robust quantum error correction.
• The findings highlight the need to consider environmental radiation in the design of fault-tolerant quantum computers.