Cosmic-Ray Threat to Quantum Computing Greater than Previously Thought
(PhysicsWorld) Quantum computers may need a redesign to protect them from background radiation, say physicists. After earlier experiments showed that cosmic rays can severely disrupt the operation of superconducting quantum bits (qubits), an international team led by Robert McDermott of the University of Wisconsin-Madison, US, has now concluded that a leading error-correction method is unlikely to fix the problem on its own. Instead, McDermott and colleagues suggest that a combination of shielding and changes in qubit chip design may be required to keep errors at a manageable level.
Cosmic rays have created headaches in classical computing for decades. When these energetic particles fly in from space and strike a silicon computer chip, one or more bits in the chip may change state, or flip, in ways that programmers never intended. If these errors go uncorrected, damaging glitches may result – including, in one case, injuries to passengers on a Qantas flight after a bit-flip error fed incorrect data to the aeroplane’s instruments.
Writing in Nature, the researchers suggest two possible solutions. One is to protect the quantum processor by shielding it with lead and shifting it to an underground site, as is already done for dark matter and neutrino detection experiments that are especially sensitive to radiation. Another is to reduce the sensitivity of the qubits by, for example, adding materials to the chip that can trap quasiparticles or funnel them away from the qubit substrate. “It’s a roadblock that we’re going to get over,” Wilen says, adding that the Wisconsin group plans to explore several of these mitigation strategies in the future.