#cosmicraysquantumcomputing

Cosmic Rays Quantum Computing and Gamma Rays

New Quantum Computing Threat: Cosmic Rays Gamma Rays and Quantum Computing

A recent study found that strong particles from Earth and space directly interfere with superconducting processors' sensitive quantum bits (qubits), posing a new challenge to quantum computer development. These findings suggest that Cosmic Rays Quantum Computing and gamma rays over enormous arrays of qubits are associated faults that threaten  fault-tolerant quantum computing.

This phenomena was best demonstrated by a 63-qubit chip investigation by the Beijing Academy of Quantum Information Sciences and allied Chinese organisations. They observed that high-energy particles evoke quasiparticles, fractured pairs of superconducting electrons that destabilise sensitive quantum states. These disruptions include charge-parity shifts and bit-flips.

The team found two key offenders:

Muons: Earth's upper atmosphere atoms encounter cosmic rays from deep space to form these small, fast particles. They can sneak between people and buildings.

Terrestrial gamma rays: Supernovas and radioactive decay create these strong energy explosions, which most materials can handle.

Researchers inserted muon detectors in the quantum device's dilution refrigerator to distinguish these two radiation types. Gamma rays caused 81.6% of quasiparticle bursts and muons 18.4%. Muon-induced events were unaffected, whereas lead insulation on the refrigerator dramatically reduced gamma-ray-induced ones.

Cosmo-ray muons

Origin and Nature: Cosmos-ray muons are tiny, fast particles. Cosmic Rays Quantum Computing from space impact Earth's upper atmosphere atoms, creating them. Due to their prevalence, these particles can pass through people and structures undetected.

Cosmic-ray muons hitting a superconducting quantum processor can create quasiparticle bursts (QP bursts). QP bursts simultaneously disturb multiple qubit charge parity. Broken pairs of superconducting electrons, called quasiparticles, cause bit-flip events and charge-parity shifts in qubits' unstable quantum states.

Correlated Errors: Muon impacts create correlated errors, which can cause many qubits to fail at once. Existing error correction methods presume errors are local and uncorrelated, making fault-tolerant quantum computing difficult. These methods fail when many qubits are disrupted at once, threatening reliable, long quantum calculations.

Researchers installed muon detectors in the quantum chip-containing dilution refrigerator to detect and track these events. They confirmed that certain inconsistencies matched muon collisions with these detectors. Muon QP bursts occurred every 67 seconds, according to the study.

Muons made up 18.4% of quasiparticle bursts, while terrestrial gamma rays made up 81.6%.

Shielding Effectiveness: Applying lead to the refrigerator considerably reduced gamma-ray-induced events but had no effect on muon-induced ones. This shows that lead shielding cannot totally prevent cosmic ray errors.

The results also raise doubt on Majorana qubits, which depend on stable charge-parity states and could enable fault-tolerant quantum computing. Cosmic-ray-induced charge-parity jumps may disrupt these states, threatening topologically secure systems.

Earthly gamma rays

Origin and Nature: Terrestrial gamma rays are energy explosions. Instead of cosmic-ray muons from faraway collisions, radioactive decay yields terrestrial gamma rays on Earth. They can pierce most materials and are produced by supernovas and other strong cosmic phenomena.

Superconducting quantum processors experience quasiparticle bursts (QP bursts) from terrestrial gamma rays and cosmic-ray muons. In QP bursts, broken pairs of superconducting electrons tunnelling across quantum circuits damage qubits' fragile quantum states. This causes bit-flips and charge-parity shifts.

Correlated errors, in which a particle event fails numerous qubits at once, are a major difficulty caused by these effects. Existing error correction methods assume mistakes are uncorrelated and local, making fault-tolerant quantum computing difficult. Multiple qubit interruptions render these approaches worthless, threatening the reliability of extended quantum calculations.

The researchers used in-fridge muon detectors and a 63-qubit microprocessor to differentiate muon and gamma ray effects. They observed that terrestrial gamma rays produced more QP bursts than muons. Gamma rays caused 81.6% of quasiparticle bursts, according to the study.

Effective Shielding: The study found that adding a layer of lead to the dilution refrigerator significantly reduced gamma-ray impacts. Lead shielding, developed for terrestrial gamma rays, mitigates muon-induced errors better due to its modest impact. Since laboratory materials can cause gamma-ray-induced errors, shielding would not eliminate them and would increase costs and complexity.

Why It Matters for Quantum Computing

Correlated errors—when one particle hits numerous qubits at once—are the key issue. Most quantum error correction methods assume errors are uncorrelated, local, and affect one or a few qubits. Such solutions fail when several qubits are interrupted simultaneously.

The risk of a particle hitting the array increases as quantum processors contain hundreds or thousands of qubits, making this issue more urgent. An explosion might disrupt complex quantum calculations. The paper also concerns if increasing gate fidelities or qubit coherence lengths will be enough without fixing these errors.

The findings also cast doubt on majorana qubits, which are regarded to be promising for fault-tolerant quantum computing due to their stable charge-parity states. Cosmic-ray-induced charge-parity jumps may damage topologically protected systems.

For Better Detection and Protection

Despite challenges, experts offer hope. Their multiqubit simultaneous charge-parity leap tracking method, which is sensitive to quasiparticle bursts, may also work. Scientists may be able to forecast, adjust, and detect cosmic occurrences using this technology. If a cosmic-ray strike is detected during processing, quantum error correction circuits may be redirected around the affected qubits to preserve the calculation.

Other mitigation options

Additional mitigation methods include:

Running quantum computers underground or in insulated surroundings reduces cosmic ray radiation. However, this would increase costs and complexity and not erase gamma-ray-induced flaws from lab materials.

Designing materials: The qubits' material design led to faster decay of quasiparticles than in previous investigations. Aluminium films on the Beijing team's device increase particle collection and recombination as quasiparticle traps. Chip designers may be able to reduce particle damage by intentionally building these traps and minimising quasiparticle spaces. With suitable energy gaps, materials can absorb or neutralise particle impact phonon energy waves before they reach sensitive areas.