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Color centers in wide-bandgap semiconductors are a promising class of solid-state quantum light source, many of which operate at room temperature. We examine a family of color centers in aluminum nitride, which emits close to 620 nm. We present a technique to rapidly map an ensemble of these single photon emitters, identifying all emitters, not just those with absorption dipole parallel to the laser polarization. We demonstrate a fast technique to determine their absorption polarization orientation in the c-plane, finding they are uniformly distributed in orientation, in contrast to many other emitters in crystalline materials.

Photonic waveguides with triangular cross section are being investigated for material systems such as diamond, glasses and gallium nitride, which lack easy options to create conventional rectangular nanophotonic waveguides. The design rules for optical elements in these triangular waveguides, such as couplers and gratings, are not well established. Here we present simulations of elements designed to couple light into, and out of, triangular waveguides from the vertical direction, which can be implemented with current angled-etch fabrication technology. The devices demonstrate coupling efficiencies approaching \unit{50}{\%} for light focused from a high numerical aperture objective. The implementation of such couplers will enable fast and efficient testing of closely spaced integrated circuit components., 7 pages, 5 figures

Diamond has established itself as an ideal material for photonics and optomechanics, due to its broad-band transparency and hardness. In addition, colour centres hosted within its lattice such as the nitrogen-vacancy (NV) centre, have become leading candidates for use in quantum information processing, and quantum sensors. The fabrication of nanoscale devices coupled to high quality NVs has been an outstanding challenge due to their sensitivity to magnetic, electric and strain fields within their local environment. In this work, we show how the NV centre’s ground state electron spin can be used as an embedded atomic-scale probe of the local strain caused by focused ion beam milling of nanoscale devices. This technique can thus be used to measure, and optimise material and device fabrication processes to allow diamond to reach its full potential.

Among wide-bandgap compound semiconductors, gallium nitride is the most widely available material due to its prevalence in the solid state lighting and high-speed/high-power electronics industries. It is now known that GaN is one of only a handful of materials to host color centers that emit quantum light at room temperature. In this paper, we report on a bright color center in a semi-polar gallium nitride substrate emitting at room temperature in the near-infrared. We show that a hemispherical solid immersion lens, near index matched to the semiconductor, can be used to enhance the photon collection efficiency by a factor of 4.3 ± 0.1 while improving the lateral resolution by a factor equal to the refractive index of the lens.

A device that is able to produce single photons is a 5 fundamental building block for a number of quantum technologies. 6 Significant progress has been made in engineering quantum emission in 7 the solid state, for instance, using semiconductor quantum dots as well 8 as defect sites in bulk and two-dimensional materials. Here we report 9 the discovery of a room-temperature quantum emitter embedded deep 10 within the band gap of aluminum nitride (AlN). Using spectral, 11 polarization, and photon-counting time-resolved measurements we 12 demonstrate bright (>105 counts s−1), pure (g2(0) < 0.2), and polarized 13 room-temperature quantum light emission from color centers in this 14 commercially important semiconductor.

The negatively-charged NV$^-$-center in diamond has shown great success in nanoscale, high-sensitivity magnetometry. Efficient fluorescence detection is crucial for improving the sensitivity. Furthermore, integrated devices enable practicable sensors. Here, we present a novel architecture which allows us to create NV$^-$-centers a few nanometers below the diamond surface, and at the same time in the mode field maximum of femtosecond-laser-written type-II waveguides. We experimentally verify the coupling efficiency, showcase the detection of magnetic resonance signals through the waveguides and perform first proof-of-principle experiments in magnetic field and temperature sensing. The sensing task can be operated via the waveguide without direct light illumination through the sample, which marks an important step for magnetometry in biological systems which are fragile to light. In the future, our approach will enable the development of two-dimensional sensing arrays facilitating spatially and temporally correlated magnetometry., Comment: 10 pages, 4 figures

Diamond has attracted great interest as a quantum technology platform thanks to its optically active nitrogen vacancy (NV) center. The NV's ground state spin can be read out optically, exhibiting long spin coherence times of approximate to 1 ms even at ambient temperatures. In addition, the energy levels of the NV are sensitive to external fields. These properties make NVs attractive as a scalable platform for efficient nanoscale resolution sensing based on electron spins and for quantum information systems. Diamond photonics enhance optical interactions with NVs, beneficial for both quantum sensing and information. Diamond is also compelling for microfluidic applications due to its outstanding biocompatibility, with sensing functionality provided by NVs. However, it remains a significant challenge to fabricate photonics, NVs, and microfluidics in diamond. In this Progress Report, an overview is provided of ion irradiation and femtosecond laser writing, two promising fabrication methods for diamond-based quantum technological devices. The unique capabilities of both techniques are described, and the most important fabrication results of color center, optical waveguide, and microfluidics in diamond are reported, with an emphasis on integrated devices aiming toward high performance quantum sensors and quantum information systems of tomorrow.

Apart from the outstanding perfect-for-application properties of optical transparency, hardness, bio-inertness and thermal conductivity of diamond, it has interested the scientific community due to a naturally occurring imperfection, the Nitrogen Vacancy (NV) color center. The NV center has emerged as an encouraging candidate for quantum computing due to its long electron spin coherence times and its ability to be found, manipulated and read out optically [1]. Additionally, the spin states are sensitive to magnetic and electric fields through the Zeeman and Stark effects, respectively and hence pose as a notable substrate for field sensing applications.

For an efficient single-photon source a high-count rate into a well-defined spectral and spatial mode is desirable. Here we have developed a hybrid planar Fabry-Perot microcavity by using a two-photon polymerization process (2PP) where coupling between single-photon sources (diamond colour centres) and resonance modes is observed. The first step consists of using the 2PP process to build a polymer table structure around previously characterized nitrogen-vacancy (NV) centres on top of a distributed Bragg reflector (DBR) with a high reflectivity at the NV zero-phonon line (ZPL). Afterwards, the polymer structure is covered with a silver layer to create a weak (low Q) cavity where resonance fluorescence measurements from the NVs are shown to be in good agreement with analytical and Finite Difference Time Domain (FDTD) results.

Diamond's nitrogen vacancy (NV) center is an optically active defect with long spin coherence times, showing great potential for both efficient nanoscale magnetometry and quantum information processing schemes. Recently, both the formation of buried 3D optical waveguides and high-quality single NVs in diamond were demonstrated using the versatile femtosecond laser-writing technique. However, until now, combining these technologies has been an outstanding challenge. In this Letter, we fabricate laser-written photonic waveguides in quantum grade diamond which are aligned to within micron resolution to single laser-written NVs, enabling an integrated platform providing deterministically positioned waveguide-coupled NVs. This fabrication technology opens the way toward on-chip optical routing of single photons between NVs and optically integrated spin-based sensing. (C) 2018 Optical Society of America

We demonstrated the fabrication of buried optical waveguides, Bragg grating waveguides and single NV centers in diamond using focused femtosecond laser pulses. We applied polarized Raman spectroscopy to gain insight into the stress-formed optical waveguides. We found that the optical mode is confined in the horizontal direction by the two laser-written lines, whereas in the vertical direction it is confined by the stress-induced refractive index change. An integrated waveguide-NV device was laser-fabricated, showing potential for optical magnetometry and quantum information applications.

Understanding the physical mechanisms of the refractive index modulation induced by femtosecond laser writing is crucial for tailoring the properties of the resulting optical waveguides. In this work we apply polarized Raman spectroscopy to study the origin of stress-induced waveguides in diamond, produced by femtosecond laser writing. The change in the refractive index induced by the femtosecond laser in the crystal is derived from the measured stress in the waveguides. The results help to explain the waveguide polarization sensitive guiding mechanism, as well as providing a technique for their optimization., Comment: 5 pages, 4 figures

Diamond’s nitrogen-vacancy (NV) centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and their ability to be located, manipulated and read out using light. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532- nm laser light, even at room temperature. The NV's states are isolated from environmental perturbations making their spin coherence comparable to trapped ions. An important breakthrough would be in connecting, using waveguides, multiple diamond NVs together optically. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work we show the possibility of buried waveguide fabrication in diamond, enabled by focused femtosecond high repetition rate laser pulses. We use μRaman spectroscopy to gain better insight into the structure and refractive index profile of the optical waveguides.

Diamond's nitrogen-vacancy (NV) centers show great promise in sensing applications and quantum computing due to their long electron spin coherence time and because they can be found, manipulated, and read out optically. An important step forward for diamond photonics would be connecting multiple diamond NVs together using optical waveguides. However, the inertness of diamond is a significant hurdle for the fabrication of integrated optics similar to those that revolutionized silicon photonics. In this work, we show the fabrication of optical waveguides in diamond, enabled by focused femtosecond high repetition rate laser pulses. By optimizing the geometry of the waveguide, we obtain single mode waveguides from the visible to the infrared. Additionally, we show the laser writing of individual NV centers within the bulk of diamond. We use mu-Raman spectroscopy to gain better insight on the stress and the refractive index profile of the optical waveguides. Using optically detected magnetic resonance and confocal photoluminescence characterization, high quality NV properties are observed in waveguides formed in various grades of diamond, making them promising for applications such as magnetometry, quantum information systems, and evanescent field sensors.

Optomechanically induced transparency in a single–crystal diamond microdisk supporting a 2.4 GHz mechanical mode is demonstrated. A cooperativity of C ~ 1.2 for N ~ 2 × 106 intracavity photons is reached, sufficient for coherent photon–phonon coupling., CLEO: Applications and Technology, 14–19 May 2017, San Jose, California

We demonstrate diamond microdisk optical cavities with record quality factors (Q ∼ 1 × 105) at 737 nm wavelengths near the optical transitions of implanted silicon vacancy (SiV) quantum emitters. Simulations indicate that Q/V > 1.2 × 104 is possible in these structures with optimized dimensions.

Single-crystal diamond cavity optomechanical devices are a promising example of a hybrid quantum system: by coupling mechanical resonances to both light and electron spins, they can enable new ways for photons to control solid state qubits. However, realizing cavity optomechanical devices from high quality diamond chips has been an outstanding challenge. Here we demonstrate single-crystal diamond cavity optomechanical devices that can enable photon-phonon-spin coupling. Cavity optomechanical coupling to $2\,\text{GHz}$ frequency ($f_\text{m}$) mechanical resonances is observed. In room temperature ambient conditions, these resonances have a record combination of low dissipation (mechanical quality factor, $Q_\text{m} > 9000$) and high frequency, with $Q_\text{m}\cdot f_\text{m} \sim 1.9\times10^{13}$ sufficient for room temperature single phonon coherence. The system exhibits high optical quality factor ($Q_\text{o} > 10^4$) resonances at infrared and visible wavelengths, is nearly sideband resolved, and exhibits optomechanical cooperativity $C\sim 3$. The devices' potential for optomechanical control of diamond electron spins is demonstrated through radiation pressure excitation of mechanical self-oscillations whose 31 pm amplitude is predicted to provide 0.6 MHz coupling rates to diamond nitrogen vacancy center ground state transitions (6 Hz / phonon), and $\sim10^5$ stronger coupling rates to excited state transitions., 12 pages, 5 figures

Exploring the maximum spatial resolution achievable in far-field optical imaging, we show that applying solid immersion lenses (SIL) in stimulated emission depletion (STED) microscopy addresses single spins with a resolution down to 2.4 ± 0.3 nm and with a localization precision of 0.09 nm.

Diamond's nitrogen-vacancy (NV) defect shows great promise as a quantum bit because of their long electron spin coherence time and since they can be located, manipulated and read out using optical methods. However due to its chemical inertness, a photonic manufacturing toolkit akin to silica and silicon photonics has yet to be developed for diamond. We describe how femtosecond laser fabrication can be applied to form 3D integrated optical circuits in diamond, which can optically link NV centers and help make the diamond-based quantum computer a reality. We apply μRaman spectroscopy to show amorphization in the laser-modified tracks, allowing us to produce waveguides by compressive stress between two closely spaced damage tracks. In addition, we apply confocal fluorescence microscopy to show that within the laser-inscribed waveguides, the bulk properties of the NV centers are preserved.

We demonstrate the first buried optical waveguides in diamond using focused femtosecond laser pulses. The properties of nitrogen vacancy centers are preserved in the waveguides, making them promising for diamond-based magnetometers or quantum information systems., Comment: 24 pages, 6 figures

Operating reconfigurable quantum circuits with single photon sources is a key goal of photonic quantum information science and technology. We use an integrated waveguide device containing directional couplers and a reconfigurable thermal phase controller to manipulate single photons emitted from a chromium related color center in diamond. Observation of both a wavelike interference pattern and particlelike sub-Poissionian autocorrelation functions demonstrates coherent manipulation of single photons emitted from the chromium related center and verifies wave particle duality. © 2013 American Physical Society.

We describe fabrication methods for making nano-cavities in pure diamond centered around light emitting color centers. We will present results showing how nearby structures change the emission and spin properties.

Quantum information science aims to harness uniquely quantum mechanical properties to enhance measurement and information technologies, and to explore fundamental aspects of quantum physics. Of the various approaches to quantum computing [1], photons are particularly appealing for their low-noise properties and ease of manipulation at the single qubit level [2,3]. Encoding quantum information in photons is also an appealing approach to quantum communication, metrology (eg. [4]), measurement (eg. [5]) and other quantum technologies [6]. However, the implementation of optical quantum circuits with bulk optics has reached practical limits. We have developed an integrated waveguide approach to photonic quantum circuits for high performance, miniaturization and scalability [7]. Here we report high-fidelity silica-on-silicon integrated optical realizations of key quantum photonic circuits, including two-photon quantum interference and a controlled-NOT logic gate [8]. We have demonstrated controlled manipulation of up to four photons on-chip, including highfidelity single qubit operations, using a lithographically patterned resistive phase shifter [9]. We have used this architecture to implement a small-scale compiled version of Shor's quantum factoring algorithm [10], demonstrated heralded generation of tunable four photon entangled states from a six photon input [11], a reconfigurable two-qubit circuit [12], and combined waveguide photonic circuits with superconducting single photon detectors [13]. We describe complex quantum interference behavior in multi-mode interference devices with up to eight inputs and outputs [14], and quantum walks of correlated particles in arrays of coupled waveguides [15]. Finally, we give an overview of our recent work on fundamental aspects of quantum measurement [16,17] and diamond [18,19] and nonlinear [20,21] photon sources.

The efficiency of collecting photons from optically active defect centres in bulk diamond is greatly reduced by refraction and reflection at the diamond-air interface. We report on the fabrication and measurement of a geometrical solution to the problem; integrated solid immersion lenses (SILs) etched directly into the surface of diamond. An increase of a factor of 10 was observed in the saturated count-rate from a single negatively charged nitrogen-vacancy (NV-) within a 5um diameter SIL compared with NV-s under a planar surface in the same crystal. A factor of 3 reduction in background emission was also observed due to the reduced excitation volume with a SIL present. Such a system is potentially scalable and easily adaptable to other defect centres in bulk diamond., Comment: 5 Pages, 5 figures (4 subfigures) - corrected typo

We use focused ion beam (FIB) etching to create suspended photonic crystal cavities in diamond. Our goal is to enhance and control the spontaneous emission of single N-V colour centres, which act like single ‘two-level atoms’ emitting single photons. The single nitrogen-vacancy (N-V) colour centre in diamond has attracted a lot of interest because it can be optically addressed, is photostable at room temperature and has a paramagnetic ground state whose spin can be initialized and read-out optically. By enclosing the (N-V) colour centre in a resonant cavity we aim to develop rapid readout of this optically addressable single spin. We show a technique using FIB and confocal microscopy to locate single N-V centres and discuss progress towards etching cavities around single centres.

We describe a technique for fabricating micro- and nanostructures incorporating fluorescent defects in diamond with a positional accuracy better than hundreds of nanometers. Using confocal fluorescence microscopy and focused ion beam etching, we initially locate a suitable defect with respect to registration marks on the diamond surface then etch a structure using these coordinates. We demonstrate the technique by etching an 8 m diameter hemisphere positioned with single negatively charged nitrogen-vacancy defect lies at its origin. Direct comparison of the fluorescence photon count rate before and after fabrication shows an eightfold increase due to the presence of the hemisphere. We describe a technique for fabricating micro- and nanostructures incorporating fluorescent defects in diamond with a positional accuracy better than hundreds of nanometers. Using confocal fluorescence microscopy and focused ion beam etching, we initially locate a suitable defect with respect to registration marks on the diamond surface then etch a structure using these coordinates. We demonstrate the technique by etching an 8 m diameter hemisphere positioned with single negatively charged nitrogen-vacancy defect lies at its origin. Direct comparison of the fluorescence photon count rate before and after fabrication shows an eightfold increase due to the presence of the hemisphere.

We examine some promising photonic structures for collecting and guiding light in bulk diamond. The aim of this work is to optimize single photon sources and single spin read-out from diamond color centers, specifically NV− centers. We review the modeling and fabrication (by focused ion beam and reactive ion etching) of solid immersion lenses, waveguides and photonic crystal cavities in monolithic diamond. We examine some promising photonic structures for collecting and guiding light in bulk diamond. The aim of this work is to optimize single photon sources and single spin read-out from diamond color centers, specifically NV− centers. We review the modeling and fabrication (by focused ion beam and reactive ion etching) of solid immersion lenses, waveguides and photonic crystal cavities in monolithic diamond.

The Hobart FMP-1 Automatic Meat Analyzer has been developed for rapid (approximately 5 min), simultaneous determination of the fat, moisture and protein content of meat and meat products. Results were compared with those using official AOAC methods for raw beef and pork and cooked sausage samples. Analyses of the data indicated that, except for determination of fat content of raw pork and protein content of raw beef, the Hobart FMP-1 was not significantly different from the official AOAC methods within the sampling parameters studied. From a practical meat operations standpoint, these differences were not considered to be of major concern as the machine can be calibrated to adjust for bias.

Diamond color centers show promise in quantum photonics applications. However practical implementation is limited by low photon collection efficiency. We report precise fabrication of structures which substantially increase collection efficiency from color centers. © 2010 Optical Society of America.

We have developed an integrated waveguide approach to photonic quantum circuits for high performance, miniaturization and scalability. We have begun to address the challenges of scaling up quantum circuits using new insights into how controlled operations can be efficiently realised, and demonstrated Shor's algorithm with consecutive CNOT gates and the iterative phase estimation algorithm. We have shown how quantum circuits can be reconfigured, using thermo-optic phase shifters to realise a highly reconfigurable quantum circuit able to perform almost any function on two photonic qubits, and electro-optic phase shifters in lithium niobate to rapidly manipulate the path and polarisation of telecomm wavelength single photons. We have addressed miniaturisation using multimode interference coupler architectures to directly implement NxN Hadamard operations and the `Boson sampling problem', and by using high refractive index contrast materials such as SiOxNy, in which we have implemented quantum walks of correlated photons, and Si, in which we have demonstrated generation of orbital angular momentum states of light. We have incorporated microfluidic channels for the delivery of samples to measure the concentration of a blood protein with entangled states of light. We have begun to address the integration of superconducting single photon detectors and diamond and non-linear single photon sources. Finally, we give an overview of recent work on fundamental aspects of quantum measurement, including a quantum version of Wheeler's delayed choice experiment.

Diamond is an exceptional material due to its hardness, high thermal conductivity and transparency from the UV to far IR. Recently it has caught the attention of the scientific community because it is the host of different color centers that can be used for magnetic sensing applications and quantum computing [1]. One of the most promising of these defects is the nitrogen-vacancy (NV) center. The electrons of the NV center, largely localized at the vacancy site, combine to form a spin triplet, which can be polarized with 532-nm laser light. The NV's states are isolated from environmental perturbations, making their spin coherence times long even at room temperature. The NVs can be easily initialized, manipulated and read out using light. Therefore, an important breakthrough would be in connecting, using optical waveguides, multiple diamond NVs.

Research was conducted to determine the influence of odor sources present in the vicinity of meat during slaughter, storage, shipping and handling, on the odor and flavor of beef. In most cases, outside samples and ground composites scored higher in off-flavor intensity than did inside samples. Fat sample results were similar but exhibited greater variation. Odor scores followed a similar pattern. Ammonia was found the easiest source of odor and flavor to detect; cigarette smoke, butts and ashes, automobile exhaust, kerosene and paint were also easily detected. Spoiled meat could be detected as imparting an off-odor and off-flavor, but the source was not easily identified. Other variables (e.g., silage, soap, rancid grease) showed little evidence of causing off-flavor or off-odor to the meat. The influence of storage time and exposure pre- or post-rigor seemed negligible in most cases.