US Patent 9416005 Solid state material

A solid state system comprising a host material and a quantum spin defect, wherein the quantum spin defect has a T2 at room temperature of about 300 μs or more and wherein the host material comprises a layer of single crystal CVD diamond having a total nitrogen concentration of about 20 ppb or less, wherein the surface roughness, Rq of the single crystal diamond within an area defined by a circle of radius of about 5 μm centered on the point on the surface nearest to where the quantum spin defect is formed is about 10 nm or less, methods for preparing solid state systems and the use of single crystal diamond having a total nitrogen concentration of about 20 ppb or less in spintronic applications are described.