Nanoscale axial position and orientation measurement of hexagonal boron nitride quantum emitters using a tunable nanophotonic environment.

Color centers in hexagonal boron nitride (hBN) have emerged as promising candidates for single-photon emitters (SPEs) due to their bright emission characteristics at room temperature. In contrast to mono- and few-layeredhBN, color centers in multi-layered flakes show superior emission characteristics such as higher saturation counts and spectral stability. Here, we report a method for determining both the axial position and three-dimensional dipole orientation of SPEs in thickhBN flakes by tuning the photonic local density of states using vanadium dioxide (VO2), a phase change material. Quantum emitters under study exhibit a strong surface-normal dipole orientation, providing some insight on the atomic structure ofhBN SPEs, deeply embedded in thick crystals. Next, we optimized a hot pickup technique to reproducibly transfer thehBN flake from VO2/sapphire substrate onto SiO2/Si substrate and relocated the same emitters. Our approach serves as a practical method to systematically characterize SPEs inhBN prior to integration in quantum photonics systems.

Mid-infrared radiative emission from bright hot plasmons in graphene.

Carrier excitation and decay processes in graphene are of broad interest since relaxation pathways that are not present in conventional materials are enabled by a gapless Dirac electronic band structure. Here, we report that a previously unobserved decay pathway-hot plasmon emission-results in Fermi-level-dependent mid-infrared emission in graphene. Our observations of non-thermal contributions to Fermi-level-dependent radiation are an experimental demonstration of hot plasmon emission arising from a photo-inverted carrier distribution in graphene achieved via ultrafast optical excitation. Our calculations indicate that the reported plasmon emission process can be several orders of magnitude brighter than Planckian emission mechanisms in the mid-infrared spectral range. Both the use of gold nanodisks to promote scattering and localized plasmon excitation and polarization-dependent excitation measurements provide further evidence for bright hot plasmon emission. These findings define an approach for future work on ultrafast and ultrabright graphene emission processes and mid-infrared light source applications.

Spontaneous Exciton Valley Coherence in Transition Metal Dichalcogenide Monolayers Interfaced with an Anisotropic Metasurface.

The control of the exciton intervalley coherence renders transition metal dichalcogenides monolayers promising candidates for quantum information science. So far, generating intervalley coherence has the need for an external coherent field. Here, we theoretically demonstrate spontaneous generation (i.e., without any external field) of exciton intervalley coherence. We achieve this by manipulating the vacuum field in the vicinity of the monolayer with a designed polarization-dependent metasurface, inducing an anisotropic decay rate for in-plane excitonic dipoles. Harnessing quantum coherence and interference effects in two-dimensional materials may provide the route for novel quantum valleytronic devices.

Quantum coherence-driven self-organized criticality and nonequilibrium light localization.

Self-organized criticality emerges in dynamical complex systems driven out of equilibrium and characterizes a wide range of classical phenomena in physics, geology, and biology. We report on a quantum coherence-controlled self-organized critical transition observed in the light localization behavior of a coherence-driven nanophotonic configuration. Our system is composed of a gain-enhanced plasmonic heterostructure controlled by a coherent drive, in which photons close to the stopped-light regime interact in the presence of the active nonlinearities, eventually synchronizing their dynamics. In this system, on the basis of analytical and corroborating full-wave Maxwell-Bloch computations, we observe quantum coherence-controlled self-organized criticality in the emergence of light localization arising from the synchronization of the photons. It is associated with two first-order phase transitions: one pertaining to the synchronization of the dynamics of the photons and the second pertaining to an inversionless lasing transition by the coherent drive. The so-attained light localization, which is robust to dissipation, fluctuations, and many-body interactions, exhibits scale-invariant power laws and absence of finely tuned control parameters. We also found that, in this nonequilibrium dynamical system, the effective critical "temperature" of the system drops to zero, whereupon one enters the quantum self-organized critical regime.

Nonreciprocal Localization of Photons.

We demonstrate that it is possible to localize photons nonreciprocally in a moving photonic lattice made by spatiotemporally modulating the atomic response, where the dispersion acquires a spectral Doppler shift with respect to the probe direction. A static defect placed in such a moving lattice produces a spatial localization of light in the band gap with a shifting frequency that depends on the direction of incident field with respect to the moving lattice. This phenomenon has an impact not only in photonics but also in broader areas such as condensed matter and acoustics, opening the doors for designing new devices such as compact isolators, circulators, nonreciprocal traps, sensors, unidirectional tunable filters, and possibly even a unidirectional laser.

Thromboembolism in active ulcerative colitis.

Inflammatory bowel disease (IBD) has a range of both intestinal and extraintestinal manifestations. Thromboembolism involving the arterial and/or venous systems is rare. Early recognition and treatment of thrombosis in patients with IBD may prevent progression and minimise complications. However, clear guidelines on the duration of treatment and indications for primary prophylaxis need to be established. We report a case of a young patient with ulcerative colitis, who developed multiple site arterial and venous thrombosis, all occurring within short intervals of each other.

Totally Endovascular Management of Popliteal Artery Occlusion and Pseudoaneurysm Formation after Total Knee Replacement.

Injuries to the popliteal artery during total knee arthroplasty (TKA) are rare. We present a case of a 72-year-old man with popliteal artery thrombosis and a pseudoaneurysm presenting immediately after TKA. First-line management of acute limb ischemia is currently transitioning from open surgery to endovascular strategies such as catheter-directed thrombolysis or mechanical thrombectomy. Due to the rarity of acute limb ischemia and pseudoaneurysms after TKA, endovascular management is only reported in a few case studies. This case is distinctive by having both popliteal artery thrombosis and a pseudoaneurysm which were successfully managed entirely endovascular using AngioJet thrombolysis and a flexible covered stent. This case contributes to the evidence supporting endovascular management of this rare complication of TKA.

Publisher's Note: Coherence-Driven Topological Transition in Quantum Metamaterials [Phys. Rev. Lett. 116, 165502 (2016)].

This corrects the article DOI: 10.1103/PhysRevLett.116.165502.

Coherence-Driven Topological Transition in Quantum Metamaterials.

We introduce and theoretically demonstrate a quantum metamaterial made of dense ultracold neutral atoms loaded into an inherently defect-free artificial crystal of light, immune to well-known critical challenges inevitable in conventional solid-state platforms. We demonstrate an all-optical control, on ultrafast time scales, over the photonic topological transition of the isofrequency contour from an open to closed topology at the same frequency. This atomic lattice quantum metamaterial enables a dynamic manipulation of the decay rate branching ratio of a probe quantum emitter by more than an order of magnitude. Our proposal may lead to practically lossless, tunable, and topologically reconfigurable quantum metamaterials, for single or few-photon-level applications as varied as quantum sensing, quantum information processing, and quantum simulations using metamaterials.

Microwave-controlled efficient Raman sub-harmonic generation.

We propose a novel scheme for efficient Raman sub-harmonic generation in a system of inhomogeneously broadened atomic vapor with atoms in a closed three-level Λ-configuration. The key feature underlying Raman sub-harmonics generation is microwave-induced hyperfine coherence between the two lower level metastable states. We show explicitly how the amplitude and phase of the microwave field generate controllable spectral amplitudes of Raman sub-harmonics. Our scheme is viable in currently available atomic vapor cells thereby opening the way for efficient sub-harmonic generation in standard experimental setups.

Metasurface-Enabled Remote Quantum Interference.

An anisotropic quantum vacuum (AQV) opens novel pathways for controlling light-matter interaction in quantum optics, condensed matter physics, etc. Here, we theoretically demonstrate a strong AQV over macroscopic distances enabled by a judiciously designed array of subwavelength-scale nanoantennas-a metasurface. We harness the phase-control ability and the polarization-dependent response of the metasurface to achieve strong anisotropy in the decay rate of a quantum emitter located over distances of hundreds of wavelengths. Such an AQV induces quantum interference among radiative decay channels in an atom with orthogonal transitions. Quantum vacuum engineering with metasurfaces holds promise for exploring new paradigms of long-range light-matter interaction for atom optics, solid-state quantum optics, quantum information processing, etc.

Quantum-coherence-enhanced surface plasmon amplification by stimulated emission of radiation.

We investigate surface plasmon amplification in a silver nanoparticle coupled to an externally driven three-level gain medium and show that quantum coherence significantly enhances the generation of surface plasmons. Surface plasmon amplification by stimulated emission of radiation is achieved in the absence of population inversion on the spasing transition, which reduces the pump requirements. The coherent drive allows us to control the dynamics and holds promise for quantum control of nanoplasmonic devices.

Oncological advantages of oncoplastic breast-conserving surgery in treatment of early breast cancer.

The standard approach to breast-conserving surgery is wide local excision of the tumor and radiotherapy. However, a significant number of patients require further surgery to obtain oncologically clear margins, and may obtain a poor cosmetic result following adjuvant radiotherapy. Oncoplastic techniques may result in improved cosmesis, but few studies have investigated the oncological advantage of this approach. The aim of this retrospective study was to compare tumor clearance and the need for further margin excision following standard wide local excision (group A, 121 patients), and oncoplastic breast-conserving surgery (group B, 37 patients). These techniques included therapeutic mammoplasty, sub-axillary fat pad rotation mammoplasty, thoraco-epigastric flap, and central flap. Compared to standard surgery (group A), oncoplastic techniques (group B) can be employed for significantly larger tumors (17.6 mm versus 23.9 mm, p = 0.002). Oncoplastic breast-conserving surgery results in higher mean specimen weights (58.1 g versus 231.1 g, p < 0.0001), higher specimen volumes (112.3 cm(3) versus 484.5 cm(3) , p < 0.0001), and wider clear margins (6.1 mm versus 14.3 mm, p < 0.0001), resulting in lower rates of further surgery (28.9% versus 5.4%, p = 0.002). There was no statistical increase in complication rates following oncoplastic surgery. Oncoplastic breast-conserving surgery is more successful than standard wide local excision in treating larger tumors and obtaining wider radial margins, thus reducing the need for further margin excision, which delays adjuvant therapy. There was no increase in postoperative complication rate using an oncoplastic approach.

Time-resolved surface-enhanced coherent sensing of nanoscale molecular complexes.

Nanoscale real-time molecular sensing requires large signal enhancement, small background, short detection time and high spectral resolution. We demonstrate a new vibrational spectroscopic technique which satisfies all of these conditions. This time-resolved surface-enhanced coherent anti-Stokes Raman scattering (tr-SECARS) spectroscopy is used to detect hydrogen-bonded molecular complexes of pyridine with water in the near field of gold nanoparticles with large signal enhancement and a fraction of a second collection time. Optimal spectral width and time delays of ultrashort laser pulses suppress the surface-enhanced non-resonant background. Time-resolved signals increase the spectral resolution which is limited by the width of the probe pulse and allow measuring nanoscale vibrational dephasing dynamics. This technique combined with quantum chemistry simulations may be used for the investigation of complex mixtures at the nanoscale and surface environment of artificial nanostructures and biological systems.

Remote sub-diffraction imaging with femtosecond laser filaments.

Achieving super-resolution has become a scientific imperative for remote imaging of objects and scenes needing increased detail and has motivated the development of various laser-based techniques. We demonstrate a scheme which achieves subdiffraction imaging of remote objects by using femtosecond laser filaments. The use of laser filaments for imaging is destined to have applications in many environments.

Psoriasis-induced postoperative cardiac failure.

Erythroderma-induced cardiogenic shock is a rare but known manifestation of erythrodermic psoriasis. Erythrodermic psoriasis is an aggressive form of the disease and can be precipitated by numerous factors including stress to the body. In this article we present a case of persistent severe vasodilatation after coronary artery bypass surgery that required prolonged epinephrine administration. This was caused by a flareup of erythrodermic psoriasis that was previously only controlled by methotrexate. This drug was omitted in the perioperative phase. Vasodilatation disappeared after treatment was reinstituted.

Mitral valve repair in a 55-year-old man with left lung agenesis.

We report on a 55-year-old man who was diagnosed with agenesis of the left lung in childhood. He was essentially asymptomatic until he was 53 years of age, when he became symptomatic with exertional dyspnea due to severe mitral regurgitation. We performed mitral valve repair using a median sternotomy incision approach.

Gastrobronchial fistula--a recent series.

Gastrobronchial fistula is a very rare condition with only 27 reported cases. Previous gastro-oesophageal surgery, subphrenic abscess, and gastric ulcers are the most commonly reported causes. We are reporting two recent cases of gastrobronchial fistula that presented to us. A review of the literature discussing possible causes, investigation and management of this condition is also provided.