Scientists protect quantum information in a noiseless subsystem

Theorists at Los Alamos National Laboratory have realised a general and efficient method for protecting quantum information against noise.

Theorists at the US Department of Energy’s Los Alamos National Laboratory, in collaboration with an experimental team at the Massachusetts Institute of Technology (MIT), have realised a general and efficient method for protecting quantum information against noise.

The demonstration is said to pave the way for the development of novel means for storing delicate quantum information and should further the evolution of quantum computers.

Quantum computers reportedly promise greatly increased computational speeds, which will be useful for performing critical mathematical tasks such as database searches, number factoring, and for simulating complex quantum systems.

In a paper published in Science magazine, Los Alamos researcher Lorenza Viola, Evan M. Fortunato of MIT and their colleagues described the encoding of quantum information in a physical degree of freedom protected against noise – something scientists call a ‘noiseless subsystem’ – using nuclear magnetic resonance on molecules of the amino acid alanine.

Achieving noise control is indispensable for quantum information processing, as noiseless subsystems are immune to certain types of information-corrupting ‘noise,’ which could otherwise disrupt computations that exploit fragile quantum states.

‘Previous Los Alamos and MIT research has shown that noiseless subsystems exist whenever a symmetry occurs in the noise,’ said Viola. ‘Noiseless subsystems conceptually unify the ways we think of noise control. In addition, we know that it is possible in principle to perform quantum computations without leaving the noise-protected system.

‘Our results are the first experimental step confirming that general theory, and will hopefully motivate other quantum researchers to explore practical implications of noiseless subsystems for quantum information storage and manipulation.’

According to a statement, Los Alamos National Laboratory has been a leader in theoretical and experimental quantum computation since quantum computers were first proposed in the early 1990s.

Quantum researchers use qubits, or quantum bits, as a basic unit of information and the counterpart to the binary bit in classical computing.

A three-qubit quantum device was demonstrated at Los Alamos in 1998 and in early 2000 researchers built the first seven-qubit device.

This demonstration comes on the heels of last year’s work by Knill, Laflamme, and Viola where the notion of a ‘noiseless subsystem’ was first discovered.