Stable Qubits Bring Us A Step Closer To Quantum Computers


Although quantum computing promises to revolutionize information technology, the field still has a long way to go. Quantum states allow for faster and more complex calculations, but they are very fragile.

Now, researchers from the Niels Bohr Institute have demonstrated that it is possible to have a “sturdy” quantum state which leaves the quantum information intact. The state, called a Majorana zero mode, is spread across a nanowire, and the quantum information is stored across separate locations, so measuring it in one location doesn’t affect the whole state.

Quantum computers are based on quantum bits or qubits, where information is not just stored in either single 0s or 1s, but also in a superposition of states, a combination of 0s and 1s. This property allows for increased computational power.

Unfortunately, this property is not stable. When a measurement is taken, the superpositioned quantum state collapses into either a 0 or a 1, and the qubit reverts to being a standard bit. In the Majorana zero mode, information is stored in such a way that disturbances in either location at either end of the nanowire leave the overall state “protected” against changes.

“We are investigating a new kind of particle, called a Majorana zero mode, which can provide a basis for quantum information that is protected against measurement by a special and who knows, perhaps unique property of these particles,” said professor Charles Marcus, coauthor of the research, in a statement.

“Majorana particles don’t exist as particles on their own, but they can be created using a combination of materials involving superconductors and semiconductors.”

The state was created in a 10-micro-long and 0.1-micron-thick semiconductor nanowire, which was then coated with superconducting aluminum. The nanowire was then cooled to near absolute zero and exposed to the strong magnetic field. The Majorana zero mode formed in these conditions.

“The protection is related to the exotic property of the Majorana mode that it simultaneously exists on both ends of the nanowire, but not in the middle,” says Sven Albrecht, lead author of the paper published this week in Nature. “To destroy its quantum state, you have to act on both ends at the same time, which is unlikely.”

The study demonstrates for the first time the properties of this particle, which has only been observed in 2012. The team is confident that employing this new material and technique will allow the field to develop more quickly than before.

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