The ultra-high purity of the diamond allows it to store a staggering amount of data – the equivalent of one billion Blu-Ray discs.

Diamond is one of the most promising materials for practical quantum computing systems, including memory. A particular defect in the crystal, known as a nitrogen-vacancy center, can be used to store data in the form of superconducting quantum bits (qubits), but too much nitrogen in the diamond disrupts its quantum storage capabilities.

That meant there was a trade-off to make – scientists had to create either large diamond wafers with too much nitrogen, or ultra-pure diamond wafers that are too small to be of much use for data storage. But now, researchers at Saga University and Adamant Namiki Precision Jewelery Co. in Japan have developed a new method for manufacturing ultra-high purity diamond wafers that are big enough for practical use.

With this technique, the team says the resulting diamond wafers measure 5 cm across, and have such immense data density that they can theoretically store the equivalent of a billion Blu-Ray discs. One Blu-Ray can store up to 25 GB (assuming it's single-layered), which would mean this diamond wafer should be able to store a whopping 25 exabytes (EB) of data. The company calls these wafers Kenzan Diamond.

The key is that these diamonds have a nitrogen concentration of under three parts per billion (ppb), making them incredibly pure. The researchers say that these are the largest wafers with that level of purity – most others only get to 4 mm2 (0.006 in2) at most.