Japanese researchers have found a unique method for making 5-cm (2-in) diamond wafers that might be utilized for quantum storage. The diamond’s ultra-high purity allows it to retain an incredible quantity of data — one billion Blu-Ray discs.
Diamond is one of the most promising methods for practical quantum computing systems. A nitrogen-vacancy centre in the crystal can store data in the form of superconducting quantum bits (qubits). Still, too much nitrogen in the diamond disturbs its quantum storage capabilities.
This meant that scientists had to choose between generating large diamond wafers with too much nitrogen and producing ultra-pure diamond wafers that were too tiny to process. However, Saga University and Adamant Namiki Precision Jewelery Co. in Japan have devised an innovative process for producing ultra-high purity diamond wafers large enough for practical usage.
The team claims that with this process, the final diamond wafers are 5 cm broad and have such high data density that they can theoretically hold the equivalent of a billion Blu-Ray discs. One Blu-Ray can hold up to 25 GB of data (assuming it’s single-layered); therefore, this diamond wafer should hold up to 25 exabytes (EB). Kenzan Diamond is the company’s name for these wafers.
The essential point is that these diamonds have a nitrogen content of less than three parts per billion (ppb), making them extremely pure. According to the researchers, these are the biggest wafers with that degree of purity – most others only attain 4 mm2 (0.006 in2).
This involves the development of a new production technique. Diamond wafers are created by growing crystals on a substrate material, typically a flat surface. The concern is that the diamond might break under pressure, lowering its quality. So the researchers made a very basic alteration in the new process: the substrate surface was curved like steps, which spreads the strain horizontally and prevents cracks. This enables them to produce bigger diamond wafers with higher purity.
The team expects to commercialize these diamond wafers in 2023, but they are already trying to double the diameter to 10 cm in the meanwhile.
In May, the researchers will report their findings at the International Conference on Compound Semiconductor Manufacturing Technology.