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## Building block error correction for quantum computer found

May

6

2016

It is a team of scientists from Delft University of Technology under the direction of Tim Taminiau failed to detect errors in quantum calculations and fix these errors without running the quantum information is lost thereby.

They managed to achieve this by repeatedly applying quantum error correction with electron and nuclear spins in diamond. In addition, the information was stored longer than it would have without the error correction.

The importance of the invention is high because the combination of detecting errors and correcting directly is a major challenge. When the quantum information is used to store information, the detected errors can be corrected in the conventional information afterwards. But when you actually want to do quantum computations with quantum information is the active correction is crucial. Without error correction, all data will be lost.

Julia Cramer, lead author of the study, Tweakers explains why it is so important to do error correction during a quantum computation and how it works. “The problem with quantum computer is that quantum calculations are never quite perfect. We can not completely control the interactions with the environment and when you look at a quantum state, you disturb the state or superposition,” says Cramer. The latter is now the researchers succeeded: to make a measurement that first learns about the error itself without spoiling the state.

“We quantum information first housed in multiple qubits, which we call encode That way we can compare the qubits -. They are still in the same direction or not – learn something about the error if one of them is different from the rest. , we can correct it. we managed to qubits which we have protected the state, nuclear spins in diamond, as long retain that we could immediately correct those mistakes. we did it with classical electronics. ”

QuTech TU Delft Tim Taminiau and Julia Cramer QuTech lab

“Our experiment is actually performed in a hybrid quantum computer. Our kwantumprocessortje is based on an electron spin that works with a defect in diamond, the so-called NV-center , where normally sit carbon atoms. This results in an electron, and this we have among all much longer the knee as a qubit that electron is coupled with nuclear spins in its vicinity and via which electron we can measure whether two of which nuclear spins are still the same That is the power of the experiment:.. the ability to read-out of the nuclear spins without them there suffer from. That way we only get information about the error and we have plenty of time to actively correct that mistake. ”

The arrangement to join the tests, is so constituted that the spins and electron to be checked individually. “Our diamond is in a large thermos bottle with liquid helium from just above absolute zero, four degrees, to be precise. At that temperature, we have the NV-center so well under control that we can well the electron in 95 percent of cases reading, “says Cramer. “Through microwaves we can control the spin of the electron in the diamond. By electron smart and flipping down we could control individual nuclear spins.”

“The latter is essential for the quantum computer because the mistakes other building,” says Cramer. “You always have errors in quantum calculations. To create scalable quantum computer, you must correct the errors in the system.”

Correcting errors in real time, which is where a large part of the field is now dealing with. Cramer: “It is our first managed to protect the quantum superposition against errors with real-time feedback and active correction.”

The article appears on Thursday in Nature Communications.

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