Researchers in Japan have developed a new method for making 5-cm (2-in) wafers of diamond that could be used for quantum memory. 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.