Performance remained stable out to 50 rounds of error checks.įor the second error-correction configuration, errors also occurred, but most were caught, and the precise nature of the errors was generally possible to infer. Errors still occurred, though, so the error correction isn't flawless. As the chain gained more and more qubits, it became progressively more robust, with the error rate falling by a factor of 100 between the chain of five and the chain of 21. In what's probably the clearest demonstration, the researchers started the linear error correction system with a chain of five qubits, progressively adding more until the chain reached 21 qubits. The scheme's advantage, however, is that it can detect both types of error simultaneously, so it provides more robust protection. Calculations must be discarded rather than corrected when problems are found. Determining which of the data qubits is at fault when an error is detected is more difficult. The second scheme, on the right, requires a more specific geometry, so the setup is harder to spread across larger portions of the processor. (Most processors with a higher qubit count tend to have one or more inactivated connections, either due to a manufacturing problem or a high error rate.) There are many ways to arrange these connections, with limits imposed by the qubits that have to sit at the edge of the network and thus have fewer connections. In all quantum processors, the qubits are arranged with connections to their neighbors. The results show that error correction clearly works, but we'll need a lot more qubits and a lower inherent error rate before correction is useful. Now, the team is running two different error-correction schemes on the processor. Most of the error-correction schemes involve distributing a qubit's logical information across several qubits and using additional qubits to track that information in order to identify and correct errors.īack when we visited the folks at Google's quantum computing group, they mentioned that the layout of their processor was chosen because it simplifies implementing error correction. Long-term, however, most experts expect that some form of error correction will be essential.
These errors can be caused by problems setting or reading the qubits or by the qubit losing its state during calculations. "Intermediate-scale" refers to a qubit count that is typically in the dozens, while "noisy" references the fact that current qubits frequently produce errors.
The current generation of quantum hardware has been termed "NISQ": noisy, intermediate-scale quantum processors.
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