A critical obstacle in the way of silicon quantum computers has been cleared: for the first time, three teams have built quantum circuits in silicon that exceeds the threshold of at least 99 percent reliability. As a result, silicon-based quantum computers are rising to the level of traditional quantum systems and may even surpass them in terms of scalability and stability in the future, as scientists report in the expert journal “Nature.”
QuantonComputer No longer dreams of the future: the first quantum systems have already proved they can function solve fast Compared to traditional calculators. And companies like Google and IBM are already offering commercial uses for their quantum computers. These systems use quantum bits from superconducting quasiparticles, or ions, trapped in magnetic traps as computing units.
But it has disadvantages: qubits are relatively large and susceptible to interference – their position is usually only stable for about 100 microseconds. This increases the error rate and makes it more difficult to extend quantum computers to more qubits and higher powers – so far the lies. Record Be 127 cubits.
Silicon instead of superconductors or ions
Quantum computers based on silicon can help. Because the semiconductor from which classic computer chips are made specifically enables small, stable and well-defined qubits. These quantum dots contain individual atoms or electrons whose spin direction can serve as a digital zero or one. In recent years it has become possible to use such silicon quantum bits. practical temperature personally go And keep it consistent for 35 seconds.
“In a quantum world, 35 seconds is half an eternity,” explains Andrea Morello of the University of New South Wales. The problem, however, is that previous silicon-based quantum systems are closed error prone, Individual silicon qubits achieve a reliability of 99.9 percent. However, if two of them are combined to form a logic gate, the error tolerance drops below the 99 percent threshold that is required for correct calculations.
Electron Spin and Alien Atoms
But now that has changed: Three research groups have independently developed silicon-based quantum circuits that achieve more than 99 percent reliability.
Two of these systems use the spins of individual electrons in the silicon-germanium matrix as quantum dots. The qubits of the third system arise by spin from phosphorus impurities in silicon. All three teams used magnetic fields to control the behavior of the spins and thus the qubits.
The researchers combined their two qubits into logical NOT and CNOT gates and then used standardized algorithms to test the system’s performance and susceptibility to errors. The result: Two-Quit Gates achieved a reliability of between 99.35 and 99.65 percent, as reported by the three teams. “When errors become so rare, we can detect and fix them as soon as they happen,” explains Morello, leader of one of the three research teams.
from orbit to logic gate
For their quantum circuit, Morello and his team built on previous experiments with phosphorus atoms implanted as qubits in silicon. “The two-qubit operations with this are not trivial, as these two atoms cannot be directly associated with each other,” explained the researchers. To construct a still logical gate, he used an extra electron as an intermediary. Both phosphorus qubits can entangle with this electron and thus enable an interconnection.
The two teams, led by Akito Nori from the RIKEN Research Center in Japan and Xiao Yu from the Technical University of Delft, used a different technique. Their orbitals consist of single electrons in a heterogeneous matrix of germanium-rich silicon and pure silicon. For logic gates, they brought quantum dots so close together that their spins intertwined and entanglement became possible.
To test their systems and their susceptibility to errors, the three research groups implemented a number of standardized algorithms into their silicon quantum computers – with success. In all three cases, the qubit gates proved to be reliable and operable.
Silicon quantum computers are going up
According to the scientists, these advances prove that even silicon-based quantum computers can achieve the required error tolerance. “The presented results make spin qubits competitive for the first time with superconducting circuits and ion traps,” says Sego Tarucha of the RIKEN Research Center. “This shows that silicon quantum computers are also promising candidates for large-scale quantum computers.”
Ada Warren and Sophia Iaconomo of the Virginia Polytechnic Institute see it that way. In an accompanying commentary in Nature, they write: “The results of all three groups bring silicon-based quantum information processing closer to being a practical quantum computing platform – a position that some other systems, including superconducting qubits and ion traps, have achieved.” till today.” (Nature, 2022; doi:10.1038/s41586-021-04182-Y, DOI: 10.1038/s41586-021-04273-W, doi:10.1038/s41586-021-04292-7,
Quayle: Riken, University of New South Wales
