Mikhail Lukin (right) and colleagues with their neutral-atom quantum computer.Credit: Rose Lincoln/Harvard Staff Photographer
A conveyor belt of atoms arranged in orderly rows could resolve a major stumbling block towards developing a large-scale quantum computer.
Quantum-computing technology that makes qubits from atoms wins mega investment
In a study published in Nature on 15 September1, physicists show that the system can continuously replace and replenish the individual atoms suspended in an array by laser beams called ‘optical tweezers’. Physicists have used such arrays to create some of the largest quantum computers to date — a technique called neutral-atom quantum computing — but the approach is hampered by the fact that some of the atoms inevitably get lost while they perform quantum computations.
“It is a very impressive engineering achievement in overcoming atom loss,” which will help to scale up atom-based computing, says Chao-Yang Lu, a quantum physicist at the University of Science and Technology of China in Shanghai.
Making cubits from atoms
So far, state-of-the-art results in quantum computing have typically been obtained by encoding information either in trapped ions or in superconducting circuits, the approach taken by companies such as Google and IBM. The neutral-atom technique is a relatively recent entrant to the race towards building useful quantum computers, but has begun to attract massive investment.
In the Nature paper, a team of physicists led by Mikhail Lukin at Harvard University in Cambridge, Massachusetts, created a two-dimensional array of more than 3,000 rubidium atoms, each at 9 micrometres from its neighbours, inside a high-vacuum vessel. Just below that array, they suspended a gas of rubidium atoms that could serve as a reservoir.
Using the same type of optical tweezers that keep the first array in place, the team scooped up more atoms one by one from the reservoir to create a second array in what they call the ‘preparation zone’. They then moved the new array up so that each of its atoms would be side-by-side with an atom from the first array — where they can be made to interact. Finally, they removed and discarded the first array.
A micrograph showing the operation of a ‘conveyor belt’ of atom arrays. At each step, a fresh array is created at the bottom, then brought up to interact with an existing array, which might have lost some atoms while performing quantum computation. The old array is then moved up and discarded.Credit: Neng-Chun Chiu et al/Nature
