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Making memories brings us closer to quantum computers


20 June 2013

Dr Michael Biercuk: "Our new approach addresses key issues in engineering a useful quantum memory."
Dr Michael Biercuk: "Our new approach addresses key issues in engineering a useful quantum memory."

A breakthrough which brings us closer to solving problems more complex than any current supercomputer can address, in codebreaking, physics, and clean energy, has been achieved by researchers from the University of Sydney and Dartmouth College in the US.

"This work brings us closer to creating a quantum computer powerful enough that it could one day be used in developing new materials for clean-energy distribution or in rapidly searching through massive amounts of unsorted data to identify security threats online: problems on which even today's most powerful supercomputers fail," said Dr Michael Biercuk, Director of the Quantum Control Laboratory in the University of Sydney's School of Physics and ARC Centre for Engineered Quantum Systems.

The details of how the researchers developed an entirely new way of designing a practically useful quantum memory, a key need for future quantum computers, will be published in Nature Communications on Thursday 19 June.

Ever since Nobel Prize winner Richard Feynman highlighted the potential of quantum computing in the 1980s, scientists have been attempting to build and design the hardware for large-scale quantum computers.

Quantum computing is an alternate way of performing computations which uses quantum physics to represent and process information which is stored in quantum states - for instance the "spin" of an electron in a trapped atom.

Unfortunately the very same physics that makes quantum computers potentially powerful also makes them likely to experience errors, even when quantum states are just being stored idly in memory.

The research team has demonstrated a path to what is considered a holy grail in the science community: storing those quantum states with high fidelity for exceptionally long times - even hours according to their calculations. Today, most quantum states survive for tiny fractions of a second.

"The simple-sounding task of effectively preserving quantum information in a quantum memory is a major challenge," Dr Biercuk said.

"Our new approach addresses key issues in engineering a useful quantum memory. It allows us to simultaneously achieve very low error rates and very long storage times. But our work also addresses a vital practical issue - on-demand retrieval with only a short time lag to extract the stored information," said Dr Biercuk.

The researchers have developed quantum 'firmware' appropriate to controlling a practically useful quantum memory.

"Vitally, we've shown that with our approach a user may guarantee that error never grows beyond a certain level even after very long times, so long as certain constraints are met," said Dr Biercuk.

The new results continue the team's success in bringing quantum computers closer to practical reality. Last year Dr Biercuk and colleagues demonstrated a special-purpose quantum simulator with computational potential so extraordinary it would take a standard supercomputer larger than the known universe to match it.

The team led by Dr Biercuk includes University of Sydney Honours student Jarrah Sastrawan, research fellow Dr David Hayes, and PhD student Todd Green, with the work carried out in collaboration with colleagues from Dartmouth College, Dr Kaveh Khodjasteh and Professor Lorenza Viola.


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