1911-1913, Victor Hess working on his Cosmic Ray theory.
Cosmic rays are a highly energetic atomic nucleus or other particle traveling through space at a speed approaching that of light. They originate from the Sun, from outside of the Solar System in our own galaxy, and from distant galaxies. Upon impact with Earth's atmosphere, cosmic rays produce showers of secondary particles, some of which reach the surface; although the bulk is intercepted by the magnetosphere or the heliosphere.
Cosmic rays were discovered by Victor Hess in 1912 in balloon experiments, for which he won the 1936 Nobel Prize in Physics.
Today's quantum computers are error-prone. Some scientists point their finger at the cosmic rays as a potential source of error-causing particles that are passing through earth and going through our qubits, knocking them off their superposition, often lasting only milliseconds at room or refrigeration temperature. So, if we find a mitigating device or method, we may be able to solve the error-causing problem, which propels us to quantum advantage sooner than we thought.
Physicists and other researchers at Lawrence Livermore National Laboratory (LLNL) are shedding new light on one of the major challenges to realizing the promise and potential of quantum computing — error correction. The research team linked tiny error-causing perturbations in the qubits’ charge state to the absorption of cosmic rays, a finding that already is impacting how quantum computers are designed.
"Charged impulses, even minute ones like those from cosmic rays absorbed by the system, can create a blast of (relatively) high-energy electrons that can heat up the quantum device’s substrate just long enough to disrupt the qubits and disturb their quantum states, the researchers found. When a particle impact occurs, it produces a wake of electrons in the device. These charged particles zoom through the materials in the device, scattering off atoms and producing high-energy vibrations and heat. This alters the electric field as well as the thermal and vibrational environment around the qubits, resulting in errors, DuBois explained."
“We’ve always known this was possible and a potential effect — one of many that can influence the behavior of a qubit,” DuBois added. “We even joked when we saw bad performance that maybe it’s because of cosmic rays. The significance of this research is that, given that sort of architecture, it puts some quantitative bounds on what you can expect in terms of performance for current device designs in the presence of environmental radiation.”
To view the disruptions and correctly point the finger toward the cosmic ray phenomena hypothesis, researchers sent radio frequency signals into a four qubit system and, by measuring their excitation spectrum and performing spectroscopy on them, were able to see the qubits “flip” from one quantum state to another, observing that they all shift in energy at the same time, in response to changes in the charge environment coming from Cosmic Rays.
“If our model about particle impacts is correct, then we would expect that most of the energy is converted into vibrations in the chip that propagate over long distances,” said UW-Madison graduate student Chris Wilen, the paper’s lead author. “As the energy spreads, the disturbance would lead to qubit flips that are correlated across the entire chip.”
The research work also covers the "qubit lifetime", the length of time that qubits can remain in their superposition mode (1 and 0) therefore correlated changes in the charge state with a reduction in lifetime of all the qubits in the system.
The research work concluded that quantum error correction and mitigation will entail development of mitigation strategies to protect quantum systems from correlated errors due to cosmic rays and other particle and noise impacts.
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