Quantum computers are real, but thanks to the fragility of quantum information, they can't yet do anything you couldn't do faster on a normal computer. Now, a team of researchers at the University of Sydney and Dartmouth College have found a way to make quantum information more reliable.

"In these superconducting systems, the quantum information only persists for about 100 microseconds – a tiny fraction of a second," says Dr. Michael J. Biercuk, director of the Quantum Control Laboratory in the University of Sydney’s School of Physics and ARC Centre for Engineered Quantum Systems.

This information decay, called decoherence, is a problem even when information is idle. But Biercuk and his colleagues have found a way to make quantum information persist for several hours. Their research will be published on Wednesday in Nature Communications.

Quantum computing takes advantage of the unique properties of quantum particles, creating something called "qubits" in order to do calculations. Researchers believe that this new breed of computer could one day solve certain types of problems in a fraction of the time today's classical computers can, and major progress has been made towards that goal.

For example, Google and NASA recently bought a machine created by the Canadian company D-Wave, which the inventors claim is a working quantum computer. But many scientists remain unconvinced that the D-Wave machine can outperform traditional computers – if it's even a quantum computer at all. Others, such as IBM, have built proof-of-concept quantum computers, but they are all held back by decoherence.

"Building a large-scale quantum computer requires the ability to store and manipulate quantum information with very low error probabilities," says Biercuk. In other words, you've got to have a reliable form of quantum memory.

Biercuk and company are solving the problem with what's called a quantum repeater, which can "boost" a signal representing a piece of quantum information. Others have built quantum repeaters in the past, but Biercuk says this new approach will be more reliable.

The Sydney-Dartmouth repeater is based on Ytterbium ions and a process called dynamical decoupling, which uses interference to cancel out errors. The concept has been experimentally demonstrated before, but Biercuk explains these proofs-of-concept weren't practical because they limited how often the quantum information was actually retrievable. The new method makes it possible to reliably access information stored in memory at any time without damaging it.

This is the latest in a series of discoveries in quantum memory. For example, last March a group at Yale found a way to make quantum memory writable when desired, but read-only at all other times.

Biercuk says this new method will eventually be compatible with other quantum computing techniques, including that of the Yale team. "This will require some improvements in the superconducting technology first to address a rather nefarious limiting mechanism called energy relaxation," he says. "But if that can be overcome, there is great promise that quantum repeaters could in principle leverage both superconducting qubits and our techniques."