A project of the Theoretical Chemical and Quantum Physics Group


Mr. Jesse Vaitkus, Dr. Jan Jeske, A/Prof. Jared Cole, Prof. Andrew Greentree


Marcus Doherty: Australian National University

Lloyd Hollenberg: University of Melbourne

Brief Project Outline

There are many different types of impurities in diamond, which affect its optical and structural properties. For each defect species there can be numerous configurations, which results in different absorption and emission spectrum. The most abundant impurity in diamond is nitrogen, with an important nitrogen defect being the nitrogen-vacancy (NV) centre due to its defect levels in the diamond band gap, which results in a strong zero phonon line transition.

The NV centre in diamond, which has multiple charged states, is made up of a substitutional nitrogen atom that is adjacent to a vacant carbon lattice site. The two common charged states of the defect are the neutral centre (NV0) and a centre with an extra electron (NV-). The negatively charged centre has received a lot of attention in recent years due to its possible uses as a single photon source at room temperature and as a qubit in quantum information processing.

More recently, the NV centre has been explored as a quantum limited sensor. Due to the fact that the energy levels of the defect depend on many different material and electromagnetic parameters, an NV centre can be used as a nanoscale magnetometer, electrometer, thermometer and strain sensor.

Current and recent research in the TCQP on NV centres includes:

  • Use of the NV centre for sensing fluctuating electric and magnetic fields - including the concept of a decoherence probe microscope.
  • Thermodynamic stability of the defect as a function of Fermi level and/or temperature to study the relative concentration of NV- and NV0 centres.
  • Interplay of the spin-orbit excited states of the NV- centre and phonons in the crystal using decoherence theory. Experimental demonstration of the NV- centre as a quantum limited thermometer.

NV defect in a diamond crystal

The nitrogen-vacancy centre consists of a substitutional nitrogen adjacent to a vacancy in the diamond host lattice. The charge state of the defect depends on the surrounding electronic properties of the lattice, while the spin and optical properties of the defect in turn depend on the charge state. Ab initio calculations of the thermodynamic stability of the defects in diamond can be used to make predictions of the defect concentration as a function of temperature.
Webber et al., Phys. Rev. B 85, 014102 (2012).

Decoherence microscopy

Schematic of a scanning decoherence microscopy setup. A probe qubit is scanned across the sample while its quantum state is monitored. At each point the spectral response of the qubit probe is determined and from this data, a measurement of the effective qubit Hamiltonian and decoherence as a function of probe position is obtained.
Cole and Hollenberg, Nanotechnology, 20, 495401 (2009).

Recent Publications

J. H. Cole, L. C. L. Hollenberg Scanning Quantum Decoherence Microscopy, Nanotechnology 20, 495401 (2009)

L. T. Hall, C. D. Hill, J. H. Cole, L. C.L. Hollenberg Sensing of Fluctuating Nanoscale Magnetic Fields Using NV Centres in Diamond, Phys. Rev. Lett. 103, 220802 (2009)

Webber, B.T., Per, M.C., Drumm, D.W., Hollenberg, L.C.L. and Russo, S.P. Ab initio thermodynamics calculation of the relative concentration of NV- and NV0 defects in diamond, Phys. Rev. B 85, 014102 (2012)

Plakhotnik, T., Doherty, M. W., Cole, J. H., Chapman, R. and Manson, N. B., All-Optical Thermometry and Thermal Properties of the Optically Detected Spin Resonances of the NV- Center in Nanodiamond, Nano Letters 14 4989-4996 (2014)

For more information about this project, please contact Jared Cole, Andrew Greentree or Salvy Russo.