Quantum bits in quantum computers

Nitrogen-vacancy defect for electronic and nuclear spin measurement.

The negatively charged nitrogen-vacancy (NV) defect in diamond has properties that make it an ideal sensor for measuring electronic and nuclear spins in practical applications.

NV centers have a long coherence time paramagnetic ground state that can be optically initiated (spin polarization) and the initiated electronic spin state can then be optically read out, all at room temperature. We are interested in applications with a single NV center as detector which has been realized for simple external electron spin detection and detection of nearby nuclear spins, such as nanomagnetometer.

This requires near-surface NV centers, and there is a knowledge gap in how the surface and local environment affect the properties of NV centers.

Doped fullerenes are also possible quantum bits. Our work on fullerenes began with the then controversial question of whether N and P were bound or unbound inside C60 and their resulting magnetic state, which is important if they are to be used as quantum bits. These molecules have the longest spin lifetimes reported, and several systems have been proposed for use in quantum computers. Our study was followed by a generalization of bonding/non-bonding in group V atoms to flat and curved graphitic surfaces.

Publications

• The Bulk Conversion Depth of the NV-center in Diamond: Computing a Charged Defect in a Neutral Slab
• Charged dopants in neutral supercells through substitutional donor (acceptor): nitrogen donor charging of the nitrogen-vacancy center in diamond
• Spin-polarization mechanisms of the nitrogen-vacancy center in diamond
• Small cluster model of the NV center in diamond
• Electronic structure of the nitrogen-vacancy center in diamond from first-principles theory
• Phosphorous trapped within buckminsterfullerene
• Comment on: Structural and electronic properties of endohedral phosphorus fullerene P@C60: An off-centre displacement of P inside the cage
• Bonding of atomic phosphorus to polycyclic hydrocarbons and curved graphitic surfaces