A quantum computer made by researchers in China has solved a calculation in 4.2 hours that would take a classical computer thousands of years. This demonstration of what the researchers call “quantum computational advantage” was made using six more qubits – quantum bits – than the computer used by the Google team that first demonstrated the feat in 2019.
Quantum computers have the potential to vastly exceed the abilities of classical computers for certain types of calculations, although classical computers will likely remain far better suited to day-to-day tasks. But building a stable quantum computer large enough to perform useful calculations is a complex engineering challenge.
Quantum computational advantage, also known as quantum supremacy, is the name given to the point at which a quantum computer demonstrates the ability to complete a calculation that a classical computer cannot finish in a reasonable amount of time. Google first announced that it had achieved this when its Sycamore processor simulated a quantum circuit and sampled random numbers from its output – a task that has become a benchmark for the current generation of quantum computers.
Advertisement
The Google team used 54 superconducting quantum bits to perform a calculation in minutes that would have taken a classical computer tens of thousands of years. Within months, a team from the University of Science and Technology of China (USTC) solved a larger benchmark problem that was three orders of magnitude more difficult in just 70 minutes. That team used a processor called Zuchongzhi that had 66 qubits, but only used 56 in experiments – three more than Google.
Now that same team’s upgraded Zuchongzhi 2.1 processor has used 60 qubits to solve a problem that the researchers claim is another three orders of magnitude harder than their previous experiment.
The researchers say in their paper that the upgraded processor has less “noise” and is more reliable, but that future work will look to develop error correction, which is a large hurdle for quantum computing that Google and other research teams are already working on. Researchers from USTC declined to speak to żěè¶ĚĘÓƵ.
at Imperial College London says the latest quantum computing experiment shows that good progress is being made, but points out that while Google’s research appears to have been leapfrogged it may simply not be publishing incremental improvements to its own technology. Google didn’t respond to a request for comment.
Knight says that the USTC team “seems to have improved the fidelity of their qubits, so they’re less noisy and they’re operating better”.
“With the chip they’ve got they’ve made really impressive strides, but it’s probably about to saturate. They’ve probably used up all the capability of the device they’ve got at the moment,” says Knight. He is confident that research on the next generation of machines will be going on behind closed doors.
Reference:
