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+--- Thread: Quantum computers more affected by cosmic rays than we thought (/Thread-Quantum-computers-more-affected-by-cosmic-rays-than-we-thought)
Quantum computers more affected by cosmic rays than we thought - Maxmars - 02-20-2024
If there was ever a potential for a game-changing technology, it lies in quantum computing.
But of course, this technology is new, and being 'new' means we don't have all the kinks worked out just yet.
(I say "we" like I have anything to do with it, I'm really just an interested layman.)
Cosmic rays are space-traversing particles (emanations from stars,) they rain down on us pretty much continuously, although for the most part, imperceptibly ...
We've known about cosmic rays since the early 20th century, and it wasn't that no one considered them in regard to quantum device design, their effects were just underestimated.
Quantum computers are elaborate superconducting devices, at this stage, very delicate and sensitive. Relying on quantum mechanical phenomena means a single particle strike to the device can create spontaneous (and fuzzy) data flipping in the superconducting components.
From a publication in Physics World.
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.
Now, just like in our day-to-day computing, done on solid-state devices, we have adapted to use 'error-correction' algorithms which identify and mathematically calculate corrections 'on-the-fly' so to speak. A similar approach is used in reading hard drive data, media streaming, electronic messaging, cellphone services, and the like.
However...
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.
Quantum computing uses surface code error correction, an inventive two-dimensional trick which kind of allows qubits to 'imply' neighboring data structure....
Surface code error correction works by encoding information in a flat sheet of superconducting qubits, each of which is connected to its nearest neighbours. If the error rates of individual qubit operations are low enough, it should be possible to use some of these qubits to identify and correct errors in neighbouring qubits via multi-qubit operations. The other requirement is that errors cannot be correlated – in other words, an error that affects one qubit cannot affect its neighbours at the same time.
... enter the sad news...
Unfortunately, McDermott’s team discovered that errors caused by cosmic rays and gamma rays from background radiation do not meet this second condition.
...
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.
...
...the group also encountered a thornier problem: the energy released in these strikes ultimately gets transferred to the qubit substrate in the form of phonons, which are vibrations in a material and can lead to the creation of quasiparticles. As these phonons spread, they produce other kinds of correlated errors, and these errors affect the entire millimetre-scale chip. This phenomenon is known as quasiparticle poisoning, and Wilen says it “could be really damaging for error correction” unless it can be mitigated.
Their suggested solution seems to be that quantum computing research be conducted under shielding to offer enhanced protection from cosmic ray strikes...
or ... Bury it, and/or make it less sensitive, it would appear...
But I would think they'll never eliminate all cosmic rays, since some can be tremendously energetic. Feel free to check me, if I'm mistaken.
Anyway... thanks for indulging my little foray into this tiny corner of science news.
