Andrew Greentree
RMIT University, Physics, School of Science, Faculty Member
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A detailed study of the photophysical properties of several chromium-related color centers produced within chemical vapor deposition diamond is presented. These emitters show narrow luminescence lines in the range of 740-770 nm.... more
A detailed study of the photophysical properties of several chromium-related color centers produced within chemical vapor deposition diamond is presented. These emitters show narrow luminescence lines in the range of 740-770 nm. Single-photon emission was verified with continuous and pulsed excitation with detected emission rates at saturation in the range of (2-3) × 106 counts/s, while direct lifetime measurements reveal
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ABSTRACT We report the generation of sub-surface nanouidic channels from single crystal diamond. To make the channels, we used a combination of ion-beam induced damage and annealing to create a buried, etchable graphitic layer in the... more
ABSTRACT We report the generation of sub-surface nanouidic channels from single crystal diamond. To make the channels, we used a combination of ion-beam induced damage and annealing to create a buried, etchable graphitic layer in the diamond. Either laser or focussed ion-beam milling was then used to connect to that layer, and subsequent electro-chemical etching used to remove the graphitic material. The channels had dimensions 100-200 nm thick, 100 μm wide and 300 μm long, which have a total volume around 3 pL; and were around 3 μm below the diamond surface.
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ABSTRACT Parametric amplification can be used to enhance measurement sensitivity and prepare quantum states of mechanical oscillators. We report progress towards an optoelectromechanical system with the nonlinear driving and sensitive... more
ABSTRACT Parametric amplification can be used to enhance measurement sensitivity and prepare quantum states of mechanical oscillators. We report progress towards an optoelectromechanical system with the nonlinear driving and sensitive measurement required to observe quantum behaviour.
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Systems of coupled photonic cavities have been predicted to exhibit quantum phase transitions by analogy with the Hubbard model. To this end, we have studied topologies of few (up to six) photonic cavities each containing a single... more
Systems of coupled photonic cavities have been predicted to exhibit quantum phase transitions by analogy with the Hubbard model. To this end, we have studied topologies of few (up to six) photonic cavities each containing a single two-level system. Quantum phase space diagrams are produced for these systems, and compared to mean-field results. We also consider finite effective temperature, and
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Quantum information applications place stringent demands on the development of platforms that can host them. Color centers in diamond have been identified as important media for quantum information processing. Accordingly, the... more
Quantum information applications place stringent demands on the development of platforms that can host them. Color centers in diamond have been identified as important media for quantum information processing. Accordingly, the photoluminescence properties of nitrogen-vacancy (N-V) centers in diamond created by implantation and annealing are studied at cryogenic temperatures (below 10 K). We examine high pressure high temperature and chemical
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Structured decompositions of a desired unitary operator are employed to derive control schemes that achieve certain control objectives for finite-level quantum systems using only sequences of simple control pulses such as square waves... more
Structured decompositions of a desired unitary operator are employed to derive control schemes that achieve certain control objectives for finite-level quantum systems using only sequences of simple control pulses such as square waves with finite rise and decay times or Gaussian wavepackets. The technique is applied to find control schemes that achieve population transfers for pure-state systems, complete inversions of
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Abstract Theoretical model of power radiated by a nanodiamond crystal located at the surface of a fiber shows narrow peaks that are extremely sensitive to the refractive-index of the surrounding environment suggesting an architecture for... more
Abstract Theoretical model of power radiated by a nanodiamond crystal located at the surface of a fiber shows narrow peaks that are extremely sensitive to the refractive-index of the surrounding environment suggesting an architecture for efficient refractive-index sensing.
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Figure 1: Tellurite (n = 2.025) core fibre in air cladding with a radially oriented dipole emitting at a wavelength of 700nm in the core centre and also on the cladding side of the core-cladding interface. a) Power emitted by dipole vs.... more
Figure 1: Tellurite (n = 2.025) core fibre in air cladding with a radially oriented dipole emitting at a wavelength of 700nm in the core centre and also on the cladding side of the core-cladding interface. a) Power emitted by dipole vs. core diameter. b) Capture fraction vs. core diameter. The dipole emission power captured into the guided and radiation modes of a tellurite [8] (a low melting point glass with a refractive index of 2.025 at 700nm wavelength) core fibre in air has been calculated with varying core diameters for radial, azimuthal, and longitudinal dipole ...
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ABSTRACT We propose a new type of sensor, which uses diamond containing the optically active nitrogen-vacancy (NV) centres as a laser medium. The magnetometer can be operated at room-temperature and generates light that can be readily... more
ABSTRACT We propose a new type of sensor, which uses diamond containing the optically active nitrogen-vacancy (NV) centres as a laser medium. The magnetometer can be operated at room-temperature and generates light that can be readily fibre coupled, thereby permitting use in industrial applications and remote sensing. By combining laser pumping with a radio-frequency Rabi-drive field, an external magnetic field changes the fluorescence of the NV centres. We use this change in fluorescence level to push the laser above threshold, turning it on with an intensity controlled by the external magnetic field, which provides a coherent amplification of the readout signal with very high contrast. This provides the advantage over conventional NV-based magnetometers which use fluorescence measurements, based on incoherent photon emission, and are currently experimentally limited to few $\rm{nT}/\sqrt{\rm{Hz}}$. By contrast we predict that an NV-based laser threshold magnetometer with a volume of 1mm$^3$ can achieve shot-noise limited d.c.~sensitivity of $1.42~\rm{aT}/\sqrt{\rm{Hz}}$ and a.c.~sensitivity of $2.34~\rm{aT}/\sqrt{\rm{Hz}}$. We term our approach laser threshold magnetometry (LTM).
ABSTRACT The dynamics of two magnons in a Heisenberg spin chain under the influence of a non-uniform magnetic field is investigated by means of a numerical wave-function-based approach using a Holstein–Primakoff transformation. The... more
ABSTRACT The dynamics of two magnons in a Heisenberg spin chain under the influence of a non-uniform magnetic field is investigated by means of a numerical wave-function-based approach using a Holstein–Primakoff transformation. The magnetic field is localized in space such that it supports exactly one single-particle bound state. We study the interaction of this bound mode with an incoming spin wave and the interplay between transmittance, energy and momentum matching. We find analytic criteria for maximizing the interconversion between propagating single-magnon modes and true propagating two-magnon states. The manipulation of bound and propagating magnons is an essential step towards quantum magnonics.