RESUMEN
High-fidelity single-shot readout of spin qubits requires distinguishing states much faster than the T1 time of the spin state. One approach to improving readout fidelity and bandwidth (BW) is cryogenic amplification, where the signal from the qubit is amplified before noise sources are introduced and room-temperature amplifiers can operate at lower gain and higher BW. We compare the performance of two cryogenic amplification circuits: a current-biased heterojunction bipolar transistor circuit (CB-HBT), and an AC-coupled HBT circuit (AC-HBT). Both circuits are mounted on the mixing-chamber stage of a dilution refrigerator and are connected to silicon metal oxide semiconductor (Si-MOS) quantum dot devices on a printed circuit board (PCB). The power dissipated by the CB-HBT ranges from 0.1 to 1 µW whereas the power of the AC-HBT ranges from 1 to 20 µW. Referred to the input, the noise spectral density is low for both circuits, in the 15 to 30 fA/[Formula: see text] range. The charge sensitivity for the CB-HBT and AC-HBT is 330 µe/[Formula: see text] and 400 µe/[Formula: see text], respectively. For the single-shot readout performed, less than 10 µs is required for both circuits to achieve bit error rates below 10-3, which is a putative threshold for quantum error correction.
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We demonstrate a capability of deterministic doping at the single atom level using a combination of direct write focused ion beam and solid-state ion detectors. The focused ion beam system can position a single ion to within 35 nm of a targeted location and the detection system is sensitive to single low energy heavy ions. This platform can be used to deterministically fabricate single atom devices in materials where the nanostructure and ion detectors can be integrated, including donor-based qubits in Si and color centers in diamond.
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We present transport measurements of silicon MOS split gate structures with and without Sb implants. We observe classical point contact (PC) behavior that is free of any pronounced unintentional resonances at liquid He temperatures. The implanted device has resonances superposed on the PC transport indicative of transport through the Sb donors. We fit the differential conductance to a rectangular tunnel barrier model with a linear barrier height dependence on source-drain voltage and non-linear dependence on gate bias. Effects such as Fowler-Nordheim (FN) tunneling and image charge barrier lowering (ICBL) are considered. Barrier heights and widths are estimated for the entire range of relevant biases. The barrier heights at the locations of some of the resonances for the implanted tunnel barrier are between 15-20 meV, which are consistent with transport through shallow partially hybridized Sb donors. The dependence of width and barrier height on gate voltage is found to be linear over a wide range of gate bias in the split gate geometry but deviates considerably when the barrier becomes large and is not described completely by standard 1D models such as FN or ICBL effects.
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The interaction between cavity modes and optical transitions leads to new coupled light-matter states in which the energy is periodically exchanged between the matter states and the optical mode. Here we present experimental evidence of optical strong coupling between modes of individual sub-wavelength metamaterial nanocavities and engineered optical transitions in semiconductor heterostructures. We show that this behaviour is generic by extending the results from the mid-infrared (~10 µm) to the near-infrared (~1.5 µm). Using mid-infrared structures, we demonstrate that the light-matter coupling occurs at the single resonator level and with extremely small interaction volumes. We calculate a mode volume of 4.9 × 10(-4) (λ/n)(3) from which we infer that only ~2,400 electrons per resonator participate in this energy exchange process.
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An optical phased array of nanoantenna fabricated in a CMOS compatible silicon photonics process is presented. The optical phased array is fed by low loss silicon waveguides with integrated ohmic thermo-optic phase shifters capable of 2π phase shift with â¼ 15 mW of applied electrical power. By controlling the electrical power to the individual integrated phase shifters fixed wavelength steering of the beam emitted normal to the surface of the wafer of 8° is demonstrated for 1 × 8 phased arrays with periods of both 6 and 9 µm.
Asunto(s)
Lentes , Nanopartículas del Metal/química , Refractometría/instrumentación , Semiconductores , Resonancia por Plasmón de Superficie/instrumentación , Campos Electromagnéticos , Diseño de Equipo , Análisis de Falla de Equipo , Nanopartículas del Metal/efectos de la radiaciónRESUMEN
We demonstrate a two-dimensional (2D) polarization-independent resonant subwavelength grating (RSG) in a filter array. RSGs, also called guided mode resonant filters, are traditionally one-dimensional gratings; however, this leads to TE and TM resonances at different wavelengths and with different spectral shape. A 2D grating can remove the polarization dependence at normal incidence, while maintaining the desirable RSG properties of high reflectivity, narrow passband, and low sidebands without ripple. We designed and fabricated 2D gratings with near-identical responses for both polarizations at normal incidence in the telecommunication band. Ninety percent reflectivity is achieved at the resonant wavelengths.
RESUMEN
Based on a photonic-crystal slab structure, a 60 degrees photonic-crystal waveguide bend is successfully fabricated. Its bending efficiency within the photonic bandgap is measured, and near 100% efficiency is observed at certain frequencies near the valence band edge. The bending radius is ~1mum at a wavelength of lambda~1.55mum . The measured eta spectrum also agrees well with a finite-difference time-domain simulation.
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Optoelectronic devices are increasingly important in communication and information technology. To achieve the necessary manipulation of light (which carries information in optoelectronic devices), considerable efforts are directed at the development of photonic crystals--periodic dielectric materials that have so-called photonic bandgaps, which prohibit the propagation of photons having energies within the bandgap region. Straightforward application of the bandgap concept is generally thought to require three-dimensional (3D) photonic crystals; their two-dimensional (2D) counterparts confine light in the crystal plane, but not in the perpendicular z direction, which inevitably leads to diffraction losses. Nonetheless, 2D photonic crystals still attract interest because they are potentially more amenable to fabrication by existing techniques and diffraction losses need not seriously impair utility. Here we report the fabrication of a waveguide-coupled photonic crystal slab (essentially a free-standing 2D photonic crystal) with a strong 2D bandgap at wavelengths of about 1.5 microm, yet which is capable of fully controlling light in all three dimensions. These features confirm theoretical calculations on the possibility of achieving 3D light control using 2D bandgaps, with index guiding providing control in the third dimension, and raise the prospect of being able to realize unusual photonic-crystal devices, such as thresholdless lasers.
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Multiple deep wrinkles and redundant skin over the dorsal hand, wrist, and forearm develop and become of cosmetic importance to some patients as they age. Distal, dorsal superior extremity plasty was performed in selected patients by excising redundant skin and wrinkles from the dorsal hands, wrists, and forearms. The area of skin to be excised is elliptical, with the long axis of the ellipse centered over the wrinkles on the dorsal wrist. The amount of skin to be excised (i.e., the short axis of the ellipse) is determined by grasping the dorsal wrist skin, hence advancing the dorsal forearm and hand skin, while the patient flexes the wrist. This maneuver is performed to avoid excessive excision of dorsal wrist skin, which would cause decreased wrist flexion. The surgical procedure is performed with use of magnification to avoid sensory nerve injury. A relatively large volume of lidocaine is injected subcutaneously to increase the distance between the skin and nerves and therefore decrease the risk of nerve injury. The skin edges are undermined for 1 to 1(1/2) cm, and the wound is closed in two layers. The wrist is splinted in 30 to 45 degrees of extension to decrease wound tension. The procedure produces long-lasting, good to excellent cosmetic improvement and patient satisfaction. The dorsal wrist, hand, and forearm appear smoother and more youthful, and scars are relatively inconspicuous. Potential significant complications include injury to the superficial branch of the radial nerve and dorsal branch of the ulnar nerve, wound dehiscence, and decreased range of motion of the wrist. Use of magnification, a bloodless field, injection of a relatively large volume of local anesthetic (10 to 12 cc), knowledge of regional anatomy, and careful surgical technique decrease the risk of nerve injury. Avoidance of injury to the superficial sensory branches of the radial and ulnar nerves is absolutely necessary for patient satisfaction. Avoidance of injury to the wound edges with good surgical technique, postoperative immobilization with the wrist in an extended position, and subsequent advancement of the wrist to a neutral position for several weeks decrease the risk of wound dehiscence. Avoidance of excessive skin excision and prolonged wrist immobilization lowers the risk of decreasing range of motion. There have been no complications in patients who underwent this procedure.
Asunto(s)
Envejecimiento de la Piel , Cirugía Plástica , Muñeca/cirugía , Anciano , Femenino , Estudios de Seguimiento , Humanos , Persona de Mediana Edad , ReoperaciónAsunto(s)
Aseguradoras , Revisión de Utilización de Seguros , Derivación y Consulta , Humanos , Estados UnidosRESUMEN
Postoperative infections after back operations can produce complex wounds with myonecrosis, deep dead space, and exposed orthopedic hardware, bone, and dura. Three ambulatory patients with complex postoperative back wounds that resulted from infections were treated successfully with antibiotics, debridement, irrigation, and closure of deep dead space with a superior gluteal muscle flap. Several surgical maneuvers can be performed to increase the length of the superior gluteal muscle flap. The inferior portion of the gluteus maximus was left intact to preserve gluteus maximus function. All three patients obtained healed wounds. The exposed A.O. plating system was not removed. There has not been any recurrence of infections. The superior gluteal muscle flap is a reasonable flap to fill deep dead space in the low back and has some advantages over free flaps.
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Vértebras Lumbares/cirugía , Sacro/cirugía , Infección de la Herida Quirúrgica/cirugía , Anciano , Antibacterianos/uso terapéutico , Desbridamiento , Enterococcus , Femenino , Estudios de Seguimiento , Infecciones por Bacterias Grampositivas/tratamiento farmacológico , Infecciones por Bacterias Grampositivas/cirugía , Humanos , Disco Intervertebral/cirugía , Dolor de la Región Lumbar/cirugía , Masculino , Persona de Mediana Edad , Músculo Esquelético/patología , Músculo Esquelético/trasplante , Necrosis , Dispositivos de Fijación Ortopédica/efectos adversos , Parálisis , Complicaciones Posoperatorias/cirugía , Recurrencia , Trasplante de Piel , Fusión Vertebral/efectos adversos , Estenosis Espinal/cirugía , Espondilolistesis/cirugía , Infecciones Estreptocócicas/tratamiento farmacológico , Infecciones Estreptocócicas/cirugía , Colgajos Quirúrgicos , Infección de la Herida Quirúrgica/tratamiento farmacológico , Irrigación Terapéutica , Cicatrización de HeridasRESUMEN
We present the results of subwavelength antireflection surfaces etched into GaAs for use at 975 nm. These surfaces comprise linear gratings with periods less than the wavelength of light in GaAs. The structure appears as a homogeneous birefringent film. For one of the two polarizations, the film is directly analogous to the well-known quarter-wavelength antireflection coating. For the other polarization there is little effect on the surface reflectivity.
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Foreign bodies in the hand are common clinical problems. A patient with a foreign body (glass) in the hand who was initially asymptomatic subsequently experienced ulnar artery erosion, thromboemboli, digital ischemia, and skin necrosis. These complications could have been prevented by removing the glass antecedent to the ulnar artery erosion. Excellent results were obtained by removal of the glass, excision of the diseased ulnar artery segment, and primary ulnar artery anastomosis.
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Traumatismos de los Dedos/etiología , Traumatismos de los Dedos/cirugía , Cuerpos Extraños/complicaciones , Cuerpos Extraños/cirugía , Arteria Cubital/lesiones , Adulto , Vidrio , Humanos , Masculino , Tromboembolia/etiologíaRESUMEN
We have fabricated subwavelength diffractive optical elements with binary phase profiles for operation at 975 nm. The individual surface-relief features of the elements are smaller than the wavelength of light in the material. By modulating the size and spacing of the features we form artificial, gradient, effective index-of-refraction surfaces. The blazed transmission gratings were designed with rigorous coupled-wave analysis and fabricated by direct-write electron-beam lithography and reactive ion-beam etching in GaAs. The gratings have minimum features 63 nm wide. Transmission measurements show 85% diffraction efficiency into the first order.