Physicists correct quantum errors

Feb 03, 2014 by Ans Hekkenberg
Cartoon of quantum error correction with three quantum bits. First, the state is encoded in an entangled state of three quantum bits. Then the possible occurrence of errors is detected by comparing the three quantum bits. Finally the error is corrected. Credit: Fundamental Research on Matter (FOM)

Scientists from the FOM Foundation and the Technical University Delft, working together at the Kavli Institute of Nanoscience, have succeeded in detecting and correcting errors during the storage of quantum states in a diamond. This is an important step towards protecting fragile quantum information long enough to realize a functioning quantum computer. The results were published online on February 2, 2014 in Nature Nanotechnology.

Whereas a classical bit of information either takes on the value '0' or '1', quantum particles can be placed in superposition, meaning they can be either '0', '1' or '0' and '1' simultaneously. These enable powerful new ways to process information. They are, however, also extremely vulnerable to errors, such as accidental flips from '0' to '1' or changes in the phase of a superposition. Even the tiniest of such errors continuously accumulate to inevitably erase the quantum information. It is therefore crucial to timely detect and correct errors.

Quantum error correction

During classical computations errors can be detected and corrected by making redundant copies and comparing these copies at intermediate steps. At first glance such error correction seems impossible for quantum states. Quantum states cannot be faithfully copied and are irrevocably disturbed when measured. How can we know if an error occurred without ever knowing what the state actually is?

The theoretical solution, found in the nineties, is based on entanglement. This is the counterintuitive 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 disturbing the encoded itself.

Electron microscope image of the diamond quantum processor. The electron spin (purple) and nuclear spins (yellow and green) that the team used to realize quantum error correction are located in the center of the diamond half-sphere. Credit: Fundamental Research on Matter (FOM)

Spins in diamond

Dr. Tim Taminiau and his colleagues, led by FOM workgroup leader prof.dr.ir. Ronald Hanson, have now experimentally realized an error correction protocol at room temperature. Previous demonstrations required extremely low temperatures and high vacuum. The team used electrons and nuclei in a diamond. These particles carry an intrinsic property called spin, which behaves like a tiny magnet. The two possible orientations of the spin, up or down, form the values '0' and '1' of the quantum bit. The researchers entangled three of these quantum bits and could successfully detect and correct one type of quantum error at the time.

Towards applications of quantum information

The team now plans to demonstrate that quantum can be used to simultaneously protect quantum states against all types of errors for an extended period. Such long-lived can enable fundamentally secure communication and extremely fast computations.

This research was done in collaboration with researchers from the Ames Laboratory and Iowa state University in the United States.

Explore further: Scientists realize quantum bit with a bent nanotube

More information: Universal control and error correction in multi-qubit spin registers in diamond, T. H. Taminiau, J. Cramer, T. van der Sar, V. V. Dobrovitski, and R. Hanson, Nature Nanotechnology. DOI: 10.1038/nnano.2014.2 . On Arxiv: http://arxiv.org/abs/1309.5452

Related Stories

Scientists realize quantum bit with a bent nanotube

Jul 29, 2013

One of the biggest challenges in quantum science is to build a functioning quantum bit, the basic element for the quantum computer. An important theoretical candidate for such a quantum bit is using a bent ...

Playing quantum tricks with measurements

Feb 15, 2013

A team of physicists at the University of Innsbruck, Austria, performed an experiment that seems to contradict the foundations of quantum theory—at first glance. The team led by Rainer Blatt reversed a ...

At Yale, quantum computing is a (qu)bit closer to reality

Feb 15, 2012

(PhysOrg.com) -- Physicists at Yale University have taken another significant step in the development of quantum computing, a new frontier in computing that promises exponentially faster information processing ...

Recommended for you

Physicists discuss quantum pigeonhole principle

Jul 26, 2014

The pigeonhole principle: "If you put three pigeons in two pigeonholes at least two of the pigeons end up in the same hole." So where's the argument? Physicists say there is an important argument. While the ...

Unleashing the power of quantum dot triplets

Jul 24, 2014

Quantum computers have yet to materialise. Yet, scientists are making progress in devising suitable means of making such computers faster. One such approach relies on quantum dots—a kind of artificial atom, ...

Exotic state of matter propels quantum computing theory

Jul 23, 2014

So far it exists mainly in theory, but if invented, the large-scale quantum computer would change computing forever. Rather than the classical data-encoding method using binary digits, a quantum computer would process information ...

Quantum leap in lasers brightens future for quantum computing

Jul 22, 2014

Dartmouth scientists and their colleagues have devised a breakthrough laser that uses a single artificial atom to generate and emit particles of light. The laser may play a crucial role in the development of quantum computers, ...

Boosting the force of empty space

Jul 22, 2014

Vacuum fluctuations may be among the most counter-intuitive phenomena of quantum physics. Theorists from the Weizmann Institute (Rehovot, Israel) and the Vienna University of Technology propose a way to amplify ...

User comments : 0