Quantum Engineers Utilize Single Atom for Multiple Controls

UNSW researchers have showcased multiple methods to inscribe quantum information in silicon for a more adaptable design of quantum chips.

Engineers working on quantum computing at UNSW Sydney have proven that they can encode quantum information – the distinct data in a quantum computer – in four distinct ways within a single atom, located inside a silicon chip.

This accomplishment could ease some of the difficulties in operating tens of millions of quantum computing units within just a few square millimetres in a silicon quantum computer chip.

In a recent publication in Nature Communications, the engineers detailed how they utilized the sixteen quantum ‘states’ of an antimony atom to encode quantum information. Antimony, a heavy atom that can be implanted in a silicon chip, was chosen because its nucleus possesses eight unique quantum states, along with an electron having two quantum states, resulting in a total of 8 x 2 = 16 quantum states, all within a single atom. To achieve the same number of states using simple quantum bits – or qubits, the fundamental unit of quantum information – would necessitate manufacturing and coupling four of them.

Lead author Irene Fernandez de Fuentes mentioned, “The latest experiment demonstrates that all four of these techniques can be utilized in the same silicon chip using the same architecture.”

Having four different techniques offers computer engineers and physicists more versatility when creating future quantum computing chips.

“With this large antimony atom, we have complete flexibility in how we integrate it with a control structure over a silicon chip,” Prof. Morello says.

Significance of this

The quantum computers of the future will require millions, if not billions of qubits working concurrently to process and simulate models in a matter of minutes, a task that would take today’s supercomputers hundreds or even thousands of years to complete.

But the approach that Prof. Morello and other colleagues have adopted at UNSW is to design quantum computing using technology already in use to manufacture conventional computers.

“We are investing in a technology that is more challenging, slower, but for very valid reasons, one of them being the extreme density of information that it’ll be able to handle,” says Prof. Morello.

Return to the laboratory

Next, the group will use the large computational space of the antimony atom to perform quantum operations that are much more advanced than those provided by plain qubits. They plan to encode a ‘logical’ qubit within the atom – a qubit built upon more than two quantum levels, to obtain enough redundancy to detect and correct errors as they occur.

“Being able to build an error-corrected logical qubit within a single atom will be a tremendous opportunity for scaling up silicon quantum hardware to the point where it becomes commercially useful,” says Prof. Morello.

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