Marilyn Monroe famously sang that diamonds are a girl's best friend, but they are also very popular with quantum scientists—with two new research breakthroughs poised to accelerate the development of synthetic diamond-based quantum technology, improve scalability, and dramatically reduce manufacturing costs.

While silicon is traditionally used for computer and mobile phone hardware, diamond has unique properties that make it particularly useful as a base for emerging quantum technologies such as quantum supercomputers, secure communications and sensors.

However there are two key problems; cost, and difficulty in fabricating the single crystal diamond layer, which is smaller than one millionth of a meter.

A research team from the ARC Center of Excellence for Transformative Meta-Optics at the University of Technology Sydney (UTS), led by Professor Igor Aharonovich, has just published two research papers, in Nanoscale and Advanced Quantum Technologies, that address these challenges.

"For diamond to be used in quantum applications, we need to precisely engineer 'optical defects' in the diamond devices—cavities and waveguides—to control, manipulate and readout information in the form of qubits—the quantum version of classical computer bits," said Professor Aharonovich.

"It's akin to cutting holes or carving gullies in a super thin sheet of diamond, to ensure light travels and bounces in the desired direction," he said.

To overcome the "etching" challenge, the researchers developed a new hard masking method, which uses a thin metallic tungsten layer to pattern the diamond nanostructure, enabling the creation of one-dimensional photonic crystal cavities.

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