Quantum bits are noisy, and techniques to deal with this noise from quantum computers must be useful.

One possibility is not to work with single qubits, but to perform identical operations on groups of connected physical qubits, combining their noisy outputs to create a logical qubit that will be less noisy.

“Such fault tolerance allows reliable calculations with noisy components and is the key to the realization of quantum computers,” said QuTech, a Dutch-based quantum components research company separated from TU Delft University and the national research laboratory TNO.

Detail of Fujitsu diamond qubits

The qubits in question are formed by 13C nuclear rotations (orange – diagrams left and top) in diamond at 10K, with information distributed over five intricate (purple) spin qubits.

Electronic spin in the nitrogen free center (also purple) is used as an additional auxiliary qubit to detect errors, and since an error can also occur on the auxiliary qubit, a second auxiliary qubit (green, made using a 14N nuclear qubit) identifies such errors.

A custom coding system has been created for the processor, which QuTech claims can deliver the right result despite every mistake anywhere in the system – according to the company, the University of Southern California has determined that such a seven-qubit system is the smallest configuration allows error tolerance, error tolerance.

The qubits are assembled in QuTech’s 29-qubit quantum processor, in which the qubits exist in an ultra-pure diamond grown by Element Six that can maintain coherent quantum states “in minutes,” QuTech said.

“Due to the long coherence times of our qubits,” said project manager Tim Taminiau, “we could process the results of measurements on the go while the processor is running. Very few systems in the world currently have this capability. “

However, “there is still a long way to go for large-scale fault tolerance calculations,” said colleague Barbara Terhal. “True suppression of errors will require further improvements in the number of qubits and the quality of operations.

In addition to the demonstration, the researchers seek to take a modular approach, connecting multiple processor-like processors into a larger one through optical quantum connections, all controlled by conventional control electronics.

“Making many copies of small processors and connecting them together in one large quantum computer is a flexible way to meet the challenge of increasing the number of qubits,” said Taminiau, adding that QuTech already has the technology to interconnect and work on others. necessary parts.

The work was published on “Error-resistant operation of a logical qubit in a diamond quantum processor‘in kind (full access payment required).

Images provided with the kind assistance of QuTech


Diamond qubits are fault-tolerant

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