Two new research breakthroughs will accelerate the development of synthetic diamond-based quantum technology, which is set to improve scalability and drastically reduce manufacturing costs.
Computer and mobile phone hardware often relies on silicon, but diamond has specific properties that make it useful as a base for quantum technologies like quantum supercomputers, secure communications and sensors.
There are two major barriers to this approach. First, it is difficult to fabricate the single crystal diamond layer, which is less than one millionth of a metre, and second, the costs are high.
New Research Papers
Two new research papers coming from the ARC Centre of Excellence for Transformative Meta-Optics at the University of Technology Sydney (UTS) have been recently published addressing these issues. The research team is led by Professor Igor Aharonovich, and the papers were published in Nanoscale and Advanced Quantum Technologies.
“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 continued.
The team was able to create one-dimensional photonic crystal cavities by developing a new hard masking method, which relies on a thin metallic tungsten layer to pattern the diamond nanostructure.
UTS PhD candidate Blake Regan is lead author of the Nanoscale paper.
“The use of tungsten as a hard mask addresses several drawbacks of diamond fabrication. It acts as a uniform restraining conductive layer to improve the viability of electron beam lithography at nanoscale resolution,” said Regan.
According to Regan, the team is offering the first evidence of the growth of a single crystal diamond structure from a polycrystalline material through a bottom up approach.
“It also allows the post-fabrication transfer of diamond devices onto the substrate of choice under ambient conditions. And the process can be further automated, to create modular components for diamond-based quantum photonic circuitry,” he continued.
Advantages of New Approach
The 30nm-wide tungsten layer is about 10,000 times thinner than a human hair. Despite this, it enabled a diamond etch of over 300nm, which is a record selectivity for diamond processing.
One of the other big advantages of this approach is that the removal of the tungsten mask does not require the use of hydrofluoric acid, which is an extremely dangerous acid currently in use. Because of this, the safety and accessibility of the diamond nanofabrication process is improved dramatically.
In order to improve the cost and scalability, the team managed to grow single crystal diamond photonic structures with embedded quantum defects from a polycrystalline substrate.
UTS PhD candidate Milad Nonahal is lead author of the study published in Advanced Quantum Technologies.
“To the best of our knowledge, we offer the first evidence of the growth of a single crystal diamond structure from a polycrystalline material using a bottom up approach — like growing flowers from seed,” he added.
UTS Dr. Mehran Kianinia is a senior author on the second study.
“Our method eliminates the need for expensive diamond materials and the use of ion implantation, which is key to accelerating the commercialisation of diamond quantum hardware” Kianinia said.
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