Room temperature coherent control of defect spin qubits in silicon carbide

The search for electron spin qubits A point defect in diamond known as the nitrogen-vacancy (N-V) centre has generated a great deal of interest because it has a highly localized electronic spin state with quantum properties that can be easily accessed at room temperature. The search is on for similar defects in other semiconductors that are easier to grow and process into devices than diamond, or that offer alternative functionalities. Here Koehl et al . describe a new range of defect spin states in silicon carbide that can be optically addressed in the telecommunications wavelength range and coherently controlled up to room temperature. Their spin coherence properties are comparable to those of the diamond N-V centre, and silicon carbide is a material for which extensive microfabrication processes already exist in the semiconductor industry. These materials are therefore promising candidates for photonic, spintronic and quantum information applications. Electronic spins in semiconductors have been used extensively to explore the limits of external control over quantum mechanical phenomena 1 . A long-standing goal of this research has been to identify or develop robust quantum systems that can be easily manipulated, for future use in advanced information and communication technologies 2 . Recently, a point defect in diamond known as the nitrogen–vacancy centre has attracted a great deal of interest because it possesses an atomic-scale electronic spin state that can be used as an individually addressable, solid-state quantum bit (qubit), even at room temperature 3 . These exceptional quantum properties have motivated efforts to identify similar defects in other semiconductors, as they may offer an expanded range of functionality not available to the diamond nitrogen–vacancy centre 4 . Notably, several defects in silicon carbide (SiC) have been suggested as good candidates for exploration, owing to a combination of computational predictions and magnetic resonance data 4 , 5 , 6 , 7 , 8 , 9 , 10 . Here we demonstrate that several defect spin states in the 4H polytype of SiC (4H-SiC) can be optically addressed and coherently controlled in the time domain at temperatures ranging from 20 to 300 kelvin. Using optical and microwave techniques similar to those used with diamond nitrogen–vacancy qubits, we study the spin-1 ground state of each of four inequivalent forms of the neutral carbon–silicon divacancy, as well as a pair of defect spin states of unidentified