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Still waiting patiently for quantum computing to bring about the next revolution in digital processing power? We might now be a little closer, with a discovery that could help us build quantum computers at mass scale.
Scientists have refined a technique using diamond defects to store information, adding silicon to make the readouts more accurate and suitable for use in the quantum computers of the future.
To understand how the new process works, you need to go back to the basics of the quantum computing vision: small particles kept in a state of superposition, where they can represent both 1, 0, and a combination of the two at the same time.
These quantum bits, or qubits, can process calculations on a much grander scale than the bits in today’s computer chips, which are stuck representing either 1 or 0 at any one time.
Getting particles in a state of superposition long enough for us to actually make use of them has proved to be a real challenge for scientists, but one potential solution is through the use of diamond as a base material.
The idea is to use tiny atomic defects inside diamonds to store qubits, and then pass around data at high speeds using light – optical circuits rather than electrical circuits.
Diamond-defect qubits rely on a missing carbon atom inside the diamond lattice which is then replaced by an atom of some other element, like nitrogen. The free electrons created by this defect have a magnetic orientation that can be used as a qubit.
So far so good, but our best efforts so far haven’t been accurate enough to be useful, because of the broad spectrum of frequencies in the light emitted – and that’s where the new research comes in.
Scientists added silicon to the qubit creation process, which emits a much narrower band of light, and supplies the precision that quantum computing requires.
At the moment, these silicon qubits don’t keep their superposition as well, but the researchers are hopeful this can be overcome by reducing their temperature to a fraction of a degree above absolute zero.
“The dream scenario in quantum information processing is to make an optical circuit to shuttle photonic qubits and then position a quantum memory wherever you need it,” says one of the team, Dirk Englund from MIT. “We’re almost there with this. These emitters are almost perfect.”
In fact, the researchers produced defects within 50 nanometres of their ideal locations on average, which is about one thousandth the size of a human hair.
Being able to etch defects with this kind of precision means the process of building optical circuits for quantum computers then becomes more straightforward and feasible.
If the team can improve on the promising results so far, diamonds could be the answer to our quantum computing needs: they also naturally emit light in a way that means qubits can be read without having to alter their states.
You still won’t be powering up a quantum laptop anytime soon, but we’re seeing real progress in the study of the materials and techniques that might one day bring this next-generation processing power to the masses.
The research has been published in Nature Communications.