School of Physics - Research Publications
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ItemControlled single electron transfer between Si:P dots(AMER INST PHYSICS, 2006-05-08)We demonstrate electrical control of Si:P double dots in which the potential is defined by nanoscale phosphorus-doped regions. Each dot contains approximately 600 phosphorus atoms and has a diameter close to 30nm. On application of a differential bias across the dots, electron transfer is observed, using single electron transistors in both dc and rf modes as charge detectors. With the possibility to scale the dots down to a few and even single atoms these results open the way to a new class of precision-doped quantum dots in silicon.
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ItemThe effect of ion implantation on thermally stimulated currents in polycrystalline CVD diamond(ELSEVIER SCIENCE SA, 2003-01-01)
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ItemP2 dimer implantation in silicon:: A molecular dynamics study(ELSEVIER SCIENCE BV, 2006-10)
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ItemStark shift control of single optical centers in diamond(AMERICAN PHYSICAL SOC, 2006-08-25)Lifetime-limited optical excitation lines of single nitrogen-vacancy (NV) defect centers in diamond have been observed at liquid helium temperature. They display unprecedented spectral stability over many seconds and excitation cycles. Spectral tuning of the spin-selective optical resonances was performed via the application of an external electric field (i.e., the Stark shift). A rich variety of Stark shifts were observed including linear as well as quadratic components. The ability to tune the excitation lines of single NV centers has potential applications in quantum information processing.
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ItemRoom-temperature coherent coupling of single spins in diamond(NATURE PUBLISHING GROUP, 2006-06)
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ItemDiamond nanocrystals formed by direct implantation of fused silica with carbon(AMER INST PHYSICS, 2001-09-15)We report synthesis of diamond nanocrystals directly from carbon atoms embedded into fused silica by ion implantation followed by thermal annealing. The production of the diamond nanocrystals and other carbon phases is investigated as a function of ion dose, annealing time, and annealing environment. We observe that the diamond nanocrystals are formed only when the samples are annealed in forming gas (4% H in Ar). Transmission electron microscopy studies show that the nanocrystals range in size from 5 to 40 nm, depending on dose, and are embedded at a depth of only 140 nm below the implanted surface, whereas the original implantation depth was 1450 nm. The bonding in these nanocrystals depends strongly on cluster size, with the smaller clusters predominantly aggregating into cubic diamond structure. The larger clusters, on the other hand, consist of other forms of carbon such as i-carbon and n-diamond and tend to be more defective. This leads to a model for the formation of these clusters which is based on the size dependent stability of the hydrogen-terminated diamond phase compared to other forms of carbon. Additional studies using visible and ultraviolet Raman Spectroscopy, optical absorption, and electron energy loss spectroscopy reveal that most samples contain a mixture of sp2 and sp3 hybridized carbon phases.
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ItemCritical components for diamond-based quantum coherent devices(IOP PUBLISHING LTD, 2006-05-31)
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ItemCoherent population trapping of single spins in diamond under optical excitation(AMER PHYSICAL SOC, 2006-12-15)Coherent population trapping is demonstrated in single nitrogen-vacancy centers in diamond under optical excitation. For sufficient excitation power, the fluorescence intensity drops almost to the background level when the laser modulation frequency matches the 2.88 GHz splitting of the ground states. The results are well described theoretically by a four-level model, allowing the relative transition strengths to be determined for individual centers. The results show that all-optical control of single spins is possible in diamond.
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ItemProgress in silicon-based quantum computing(ROYAL SOC, 2003-07-15)We review progress at the Australian Centre for Quantum Computer Technology towards the fabrication and demonstration of spin qubits and charge qubits based on phosphorus donor atoms embedded in intrinsic silicon. Fabrication is being pursued via two complementary pathways: a 'top-down' approach for near-term production of few-qubit demonstration devices and a 'bottom-up' approach for large-scale qubit arrays with sub-nanometre precision. The 'top-down' approach employs a low-energy (keV) ion beam to implant the phosphorus atoms. Single-atom control during implantation is achieved by monitoring on-chip detector electrodes, integrated within the device structure. In contrast, the 'bottom-up' approach uses scanning tunnelling microscope lithography and epitaxial silicon overgrowth to construct devices at an atomic scale. In both cases, surface electrodes control the qubit using voltage pulses, and dual single-electron transistors operating near the quantum limit provide fast read-out with spurious-signal rejection.