September 30, 2022

Cosmic rays may cause decoherence in qubits

Researchers at MIT, MIT Lincoln Laboratory, and Pacific Northwest National Laboratory (PNNL) have found that a qubit’s performance may soon hit a wall because of the low-level, otherwise harmless background radiation that is emitted by trace elements in concrete walls and incoming cosmic rays.

Superconducting qubits are electrical circuits made from superconducting materials. They comprise multitudes of paired electrons, known as Cooper pairs, that flow through the circuit without resistance and work together to maintain the qubit’s tenuous superposition state. If the circuit is heated or otherwise disrupted, electron pairs can split up into “quasiparticles,” causing decoherence in the qubit that limits its operation.

There are many sources of decoherence that could destabilize a qubit, such as fluctuating magnetic and electric fields, thermal energy, and even interference between qubits.

Scientists have long suspected that very low levels of radiation may have a similar destabilizing effect in qubits.

The paper has been published in Nature.

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