Quantum error detection gets diamond breakthrough from Dutch scientists

A working quantum computer took a step closer this week with the announcement of improvements in detecting and subsequently correcting errors that occur during the storage process of quantum states.

Scientists of the Stichting Foundation for Fundamental Research on Matter (FOM) and the Delft University of Technology in the Netherlands have succeeded in detecting and subsequently correcting errors that occur during the storage process of quantum states onto diamonds.

It's an extremely important step in the process of protecting vulnerable quantum information, which in time, could lead to the creation of an actual working quantum computer, according to the university.

The importance of error detection

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A classic bit of information has the value 0 or 1. A quantum particle, however, can be in a superposition of two states simultaneously, effectively meaning that it can be 0, 1, or even 0 and 1 at the same time.

These quantum bits allow for a powerful new way of information processing, however, they're very susceptible to errors, such as the value of the bit suddenly changing.

Even the smallest of errors can pile up, causing the quantum information to be lost forever, which has made this method of storage promising, but very unreliable to date. Consequently, it is extremely important that any errors are detected and corrected in a timely manner.

The main problem with quantum error detection is that errors cannot be detected and corrected by making extra copies of the bits to check against, as is done with standard calculations.

A quantum state cannot be faithfully copied and – adding to the complexity – its state will be changed at the second it is measured. And if you can't measure the state, it is virtually impossible to detect an error.

The theoretical solution to this problem was found way back in the 1990s, and is based on entanglement. This is the counter-intuitive phenomenon that quantum systems can become so strongly connected that they can no longer be described separately.

By encoding the quantum state in an entangled state of multiple quantum bits it is possible to compare the states of the quantum bits to detect errors, without measuring or changing the encoded quantum state itself.

Diamonds are key

Together with his colleagues, Dr Tim Ta Taminiau — under the supervision of FOM workgroup leader Professor Ronald Hanson — has succeeded in applying this quantum error correction at room temperature.

Previous demonstrations had succeeded in applying the correction, but only at extremely low temperatures and in a near vacuum.

For their method at room temperature, the team used electrons and nuclei found in a diamond. These particles have an intrinsic property much like a tiny magnet, called a spin. The two possible directions of this spin, upwards or downwards, form the values 0 and 1 of the quantum bit.

The researchers entangled three quantum bits, allowing them to demonstrate that quantum errors can be detected and corrected.

The researchers are currently planning on expanding the quantum error correction, to allow them to protect quantum states against all types of errors simultaneously. A successful outcome of this project has a world-changing potential.

Succeeding in preserving quantum information free of errors for a long period of time, will pave the way for fundamentally safe communication (for example, very hard to hijack) and lightning fast calculations, which will change the world of technology as we know it.

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