Polariton Condensation in Gap-Confined States of Photonic Crystal Waveguides.

The development of patterned multiquantum well heterostructures in GaAs/AlGaAs waveguides has recently made it possible to achieve exciton-polariton condensation in a topologically protected bound state in the continuum (BIC). Polariton condensation was shown to occur above a saddle point of the two-dimensional polariton dispersion in a one-dimensional photonic crystal waveguide. A rigorous analysis of the condensation phenomenon in these systems, as well as the role of the BIC, is still missing. In the present Letter, we theoretically and experimentally fill this gap by showing that polariton confinement resulting from the negative effective mass and the photonic energy gap in the dispersion play a key role in enhancing the relaxation toward the condensed state. In fact, our results show that low-threshold polariton condensation is achieved within the effective trap created by the exciting laser spot, regardless of whether the resulting confined mode is long-lived (polariton BIC) or short-lived (lossy mode). In both cases, the spatial quantization of the polariton condensate and the threshold differences associated to the corresponding state lifetime are measured and characterized. For a given negative mass, a slightly lower condensation threshold from the polariton BIC mode is found and associated to its reduced radiative losses, as compared to the lossy one.

Polariton Bose-Einstein condensate from a bound state in the continuum.

Bound states in the continuum (BICs)1-3 are peculiar topological states that, when realized in a planar photonic crystal lattice, are symmetry-protected from radiating in the far field despite lying within the light cone4. These BICs possess an invariant topological charge given by the winding number of the polarization vectors5, similar to vortices in quantum fluids such as superfluid helium and atomic Bose-Einstein condensates. In spite of several reports of optical BICs in patterned dielectric slabs with evidence of lasing, their potential as topologically protected states with theoretically infinite lifetime has not yet been fully exploited. Here we show non-equilibrium Bose-Einstein condensation of polaritons-hybrid light-matter excitations-occurring in a BIC thanks to its peculiar non-radiative nature, which favours polariton accumulation. The combination of the ultralong BIC lifetime and the tight confinement of the waveguide geometry enables the achievement of an extremely low threshold density for condensation, which is reached not in the dispersion minimum but at a saddle point in reciprocal space. By bridging bosonic condensation and symmetry-protected radiation eigenmodes, we reveal ways of imparting topological properties onto macroscopic quantum states with unexplored dispersion features. Such an observation may open a route towards energy-efficient polariton condensation in cost-effective integrated devices, ultimately suited for the development of hybrid light-matter optical circuits.

Molecular, biochemical, and proteomic analyses of transplastomic tobacco plants expressing an endoglucanase support chloroplast-based molecular farming for industrial scale production of enzymes.

The successful production of recombinant enzymes by tobacco transplastomic plants must maintain compatibility of the heterologous enzyme with chloroplast metabolism and its long-time enzyme stability. Based on previous reports, it has been taken for granted that following biolistic-transformation, homoplasticity could be obtained from the initially heteroplastic state following successive rounds of selection in the presence of the selection agent. However, several studies indicated that this procedure does not always ensure the complete elimination of unmodified wild-type plastomes. The present study demonstrates that CelK1 transplastomic plants, which were photosyntetically as active as untransformed ones, remain heteroplastomic even after repeated selection steps and that this state does not impair the relatively high-level production of the recombinant enzyme. In fact, even in the heteroplastomic state, the recombinant protein represented about 6% of the total soluble proteins (TSP). Moreover, our data also show that, while the recombinant endoglucanase undergoes phosphorylation, this post-translation modification does not have any significant impact on the enzymatic activity. Biomass storage might be required whenever the enzyme extraction process could not be performed immediately following the harvest of tobacco mature plants. In this respect, we have observed that enzyme activity in the detached leaves stored at 4 °C is maintained up to 20 weeks without significant loss of activity. These findings may have major implications in the future of chloroplast genetic engineering-based molecular farming to produce industrial enzymes in transplastomic plants.

Two-dimensional hybrid perovskites sustaining strong polariton interactions at room temperature.

Polaritonic devices exploit the coherent coupling between excitonic and photonic degrees of freedom to perform highly nonlinear operations with low input powers. Most of the current results exploit excitons in epitaxially grown quantum wells and require low-temperature operation, while viable alternatives have yet to be found at room temperature. We show that large single-crystal flakes of two-dimensional layered perovskite are able to sustain strong polariton nonlinearities at room temperature without the need to be embedded in an optical cavity formed by highly reflecting mirrors. In particular, exciton-exciton interaction energies are shown to be spin dependent, remarkably similar to the ones known for inorganic quantum wells at cryogenic temperatures, and more than one order of magnitude larger than alternative room temperature polariton devices reported so far. Because of their easy fabrication, large dipolar oscillator strengths, and strong nonlinearities, these materials pave the way for realization of polariton devices at room temperature.

Steady State Entanglement beyond Thermal Limits.

Classical engines turn thermal resources into work, which is maximized for reversible operations. The quantum realm has expanded the range of useful operations beyond energy conversion, and incoherent resources beyond thermal reservoirs. This is the case of entanglement generation in a driven-dissipative protocol, which we hereby analyze as a continuous quantum machine. We show that for such machines the more irreversible the process, the larger the concurrence. Maximal concurrence and entropy production are reached for the hot reservoir being at negative effective temperature, beating the limits set by classic thermal operations on an equivalent system.

Standardisation of minimal residual disease in multiple myeloma.

The assessment of the effectiveness of chemotherapy in oncology cannot disregard the concept of minimal residual disease (MRD). In fact, the efforts of numerous scientific groups all over the world are currently focusing on this issue, with the sole purpose of defining sensitive, effective assessment criteria that are, above all, able to give acceptable, easily repeatable results worldwide. Regarding this issue, especially with the advent of new drugs, multiple myeloma is one of the haematologic malignancies for which a consensus has not yet been reached. In this review, we analyse various techniques that have been used to improve the sensitivity of response, aimed at reducing the cut-off values previously allowed, as well as serological values like serum-free light chain, or immunophenotypic tools on bone marrow or peripheral blood, like multi-parameter flow cytometry, or molecular ones such as allele-specific oligonucleotide (ASO)-qPCR and next-generation/high-throughput sequencing technologies (NGS). Moreover, our discussion makes a brief reference to promising techniques, such as mass spectrometry for identifying Ig light chain (LC) in peripheral blood, and the assessment of gene expression profile not only in defining prognostic risk at the diagnosis but also as a tool for evaluation of response.

Visible quantum plasmonics from metallic nanodimers.

We report theoretical evidence that bulk nonlinear materials weakly interacting with highly localized plasmonic modes in ultra-sub-wavelength metallic nanostructures can lead to nonlinear effects at the single plasmon level in the visible range. In particular, the two-plasmon interaction energy in such systems is numerically estimated to be comparable with the typical plasmon linewidths. Localized surface plasmons are thus predicted to exhibit a purely nonclassical behavior, which can be clearly identified by a sub-Poissonian second-order correlation in the signal scattered from the quantized plasmonic field under coherent electromagnetic excitation. We explicitly show that systems sensitive to single-plasmon scattering can be experimentally realized by combining electromagnetic confinement in the interstitial region of gold nanodimers with local infiltration or deposition of ordinary nonlinear materials. We also propose configurations that could allow to realistically detect such an effect with state-of-the-art technology, overcoming the limitations imposed by the short plasmonic lifetime.

Vaccination strategies in lymphoproliferative disorders: Failures and successes.

Anti-tumor vaccines in lymphoproliferative disorders hold out the prospect of effective tumor therapies with minimal side effects. The addition of immunotherapy to old and new chemotherapy regimens has improved both response rates and disease-free survival, leading in many cases to an extended overall survival. Ideally, an antigen that is used for vaccination would be specifically expressed in the tumor; it must have an important, causal part in the multifactorial process that leads to cancer, and it must be expressed stably even after it is attacked by the immune system. Immunotherapies, which aim to activate the immune system to kill cancer cells, include strategies to increase the frequency or potency of antitumor T cells, to overcome suppressive factors in the tumor microenvironment, and to reduce T-cell suppression systemically. In this review, we focus on the results of clinical trials of vaccination in lymphoma, and discuss potential strategies to enhance the efficacy of immunotherapy in the future.

Acoustic black hole in a stationary hydrodynamic flow of microcavity polaritons.

We report an experimental study of superfluid hydrodynamic effects in a one-dimensional polariton fluid flowing along a laterally patterned semiconductor microcavity and hitting a micron-sized engineered defect. At high excitation power, superfluid propagation effects are observed in the polariton dynamics; in particular, a sharp acoustic horizon is formed at the defect position, separating regions of sub- and supersonic flow. Our experimental findings are quantitatively reproduced by theoretical calculations based on a generalized Gross-Pitaevskii equation. Promising perspectives to observe Hawking radiation via photon correlation measurements are illustrated.

The use of ß-cell transcription factors in engineering artificial ß cells from non-pancreatic tissue.

Type 1 diabetes results from the autoimmune destruction of the insulin-producing pancreatic beta (ß) cells. Patients with type 1 diabetes control their blood glucose levels using several daily injections of exogenous insulin; however, this does not eliminate the long-term complications of hyperglycaemia. Currently, the only clinically viable treatments for type 1 diabetes are whole pancreas and islet transplantation. As a result, there is an urgent need to develop alternative therapies. Recently, cell and gene therapy have shown promise as a potential cure for type 1 diabetes through the genetic engineering of 'artificial' ß cells to regulate blood glucose levels without adverse side effects and the need for immunosuppression. This review compares putative target cells and the use of pancreatic transcription factors for gene modification, with the ultimate goal of engineering a glucose-responsive 'artificial' ß cell that mimics the function of pancreatic ß cells, while avoiding autoimmune destruction.

Fabry-Perot interferometer with quantum mirrors: nonlinear light transport and rectification.

Optical transport represents a natural route towards fast communications, and it is currently used in large scale data transfer. The progressive miniaturization of devices for information processing calls for the microscopic tailoring of light transport and confinement at length scales appropriate for upcoming technologies. With this goal in mind, we present a theoretical analysis of a one-dimensional Fabry-Perot interferometer built with two highly saturable nonlinear mirrors: a pair of two-level systems. Our approach captures nonlinear and nonreciprocal effects of light transport that were not reported previously. Remarkably, we show that such an elementary device can operate as a microscopic integrated optical rectifier.

Quantum information processing with hybrid spin-photon qubit encoding.

We introduce a scheme to perform quantum information processing that is based on a hybrid spin-photon qubit encoding. The proposed qubits consist of spin ensembles coherently coupled to microwave photons in coplanar waveguide resonators. The quantum gates are performed solely by shifting the resonance frequencies of the resonators on a nanosecond time scale. An additional cavity containing a Cooper-pair box is exploited as an auxiliary degree of freedom to implement two-qubit gates. The generality of the scheme allows its potential implementation with a wide class of spin systems.

Pancreatic transdifferentiation in porcine liver following lentiviral delivery of human furin-cleavable insulin.

Type I diabetes mellitus (TID) results from the autoimmune destruction of the insulin-producing pancreatic ß-cells. Gene therapy is one strategy being actively explored to cure TID by affording non-ß-cells the ability to secrete insulin in response to physiologic stimuli. In previous studies, we used a novel surgical technique to express furin-cleavable human insulin (INS-FUR) in the livers of streptozotocin (STZ)-diabetic Wistar rats and nonobese diabetic (NOD) mice with the use of the HMD lentiviral vector. Normoglycemia was observed for 500 and 150 days, respectively (experimental end points). Additionally, some endocrine transdifferentiation of the liver, with storage of insulin in granules, and expression of some ß-cell transcription factors (eg, Pdx1, Neurod1, Neurog3, Nkx2-2, Pax4) and pancreatic hormones in both studies. The aim of this study was to determine if this novel approach could induce liver to pancreatic transdifferentiation to reverse diabetes in pancreatectomized Westran pigs. Nine pigs were used in the study, however only one pig maintained normal fasting blood glucose levels for the period from 10 to 44 days (experimental end point). This animal was given 2.8 × 10(9) transducing units/kg of the lentiviral vector expressing INS-FUR. A normal intravenous glucose tolerance test was achieved at 30 days. Reverse-transcription polymerase chain reaction analysis of the liver tissue revealed expression of several ß-cell transcription factors, including the key factors, Pdx-1 and Neurod1, pancreatic hormones, glucagon, and somatostatin; however, endogenous pig insulin was not expressed. Triple immunofluorescence showed extensive insulin expression, as was previously observed in our studies with rodents. Additionally, a small amount of glucagon and somatostatin protein expression was seen. Collectively, these data indicate that pancreatic transdifferentiation of the liver tissue had occurred. Our data suggest that this regimen may ultimately be used clinically to cure TID, however more work is required to replicate the successful reversal of diabetes in increased numbers of pigs.

Enhanced 1.54 µm emission in Y-Er disilicate thin films on silicon photonic crystal cavities.

We introduce an Y-Er disilicate thin film deposited on top of a silicon photonic crystal cavity as a gain medium for active silicon photonic devices. Using photoluminescence analysis, we demonstrate that Er luminescence at 1.54 µm is enhanced by coupling with the cavity modes, and that the directionality of the Er optical emission can be controlled through far-field optimization of the cavity. We determine the maximum excitation power that can be coupled into the cavity to be 12 mW, which is limited by free carrier absorption and thermal heating. At maximum excitation, we observe that nearly 30% of the Er population is in the excited state, as estimated from the direct measurement of the emitted power. Finally, using time-resolved photoluminescence measurements, we determine a value of 2.3 for the Purcell factor of the system at room temperature. These results indicate that overcoating a silicon photonic nanostructure with an Er-rich dielectric layer is a promising method for achieving light emission at 1.54 µm wavelength on a silicon platform.

Young's type interference for probing the mode symmetry in photonic structures.

A revisited realization of the Young's double slit experiment is introduced to directly probe the photonic mode symmetry by photoluminescence experiments. We experimentally measure the far field angular emission pattern of quantum dots embedded in photonic molecules. The experimental data well agree with predictions from Young's interference and numerical simulations. Moreover, the vectorial nature of photonic eigenmodes results in a rather complicated parity property for different polarizations, a feature which has no counterpart in quantum mechanics.

MDR-1 polymorphisms (G2677T and C3435T) in B-chronic lymphocytic leukemia: an impact on susceptibility and prognosis.

Patients with B-chronic lymphocytic leukemia present diverse clinical features, genetic abnormalities, variable response to treatment, and heterogeneous prognosis. Novel biological markers such as IgVH mutation, CD38, and ZAP-70 expression have shown to offer important prognostic information. An altered expression of the multidrug resistance 1 may represent an additional prognostic marker. Aim of our study was to evaluate two MDR-1 gene polymorphisms: G2677T polymorphism in exon 21 and C3435T polymorphism in exon 26, to evidence if polymorphisms influence the risk of development of B-CLL and whether genomic polymorphisms provide prognostic information on the clinical progression of the disease. A total of 125 patients with B-CLL and 125 healthy subjects were enrolled in this study. The mutant homozygous 2677 TT genotype was found to be associated with the occurrence of B-CLL and higher T allele frequency in patients with B-CLL when compared with controls was observed (P=0.009). When comparing the prognostic patients' characteristics, patients with 2677 GT genotype were statistically linked to the unmutated IgVH genes (r=0.209, P=0.01). Moreover, the same genotype was correlated with lymphocyte number (r=0.269, P=0.02). Finally for the 2677GT polymorphism, the heterozygous status was associated with higher hemoglobin levels (r=0.247, P=0.005). As far the C3435T MDR1 polymorphism, we were not able to identify any significant correlation with IgVH gene status or other variables. In conclusion, MDR1 gene polymorphism could be a factor predisposing to LLC. Moreover, our findings support the possibility of considering these genomic polymorphisms as prognostic markers in patients with B-CLL.

Planar photonic crystal cavities with far-field optimization for high coupling efficiency and quality factor.

Different types of planar photonic crystal cavities aimed at optimizing the far-field emission pattern are designed and experimentally assessed by resonant scattering measurements. We systematically investigate the interplay between achieving the highest possible quality (Q) factor and maximizing the in- and out-coupling efficiency into a narrow emission cone. Cavities operate at telecommunications wavelengths, i.e. around approximately 1.55 microm, and are realized in silicon membranes. A strong modification of the far-field emission pattern, and therefore a substantial increase of the coupling efficiency in the vertical direction, is obtained by properly modifying the holes around L3, L5 and L7 type PhC cavities, as we predict theoretically and show experimentally. An optimal compromise yielding simultaneously a high Q-factor and a large coupling to the fundamental cavity mode is found for a L7-type cavity with a measured Q congruent with 62000, whose resonant scattering efficiency is improved by about two orders of magnitude with respect to the unmodified structure. These results are especially useful for prospective applications in light emitting devices, such as nano-lasers or single-photon sources, in which vertical in- and out-coupling of the electromagnetic field is necessarily required.

Fermionized photons in an array of driven dissipative nonlinear cavities.

We theoretically investigate the optical response of a one-dimensional array of strongly nonlinear optical microcavities. When the optical nonlinearity is much larger than both losses and intercavity tunnel coupling, the nonequilibrium steady state of the system is reminiscent of a strongly correlated Tonks-Girardeau gas of impenetrable bosons. Signatures of strong correlations are identified in the transmission spectrum of the system, as well as in the intensity correlations of the transmitted light. Possible experimental implementations in state-of-the-art solid-state devices are discussed.

Quantum nature of a strongly coupled single quantum dot-cavity system.

Cavity quantum electrodynamics (QED) studies the interaction between a quantum emitter and a single radiation-field mode. When an atom is strongly coupled to a cavity mode, it is possible to realize important quantum information processing tasks, such as controlled coherent coupling and entanglement of distinguishable quantum systems. Realizing these tasks in the solid state is clearly desirable, and coupling semiconductor self-assembled quantum dots to monolithic optical cavities is a promising route to this end. However, validating the efficacy of quantum dots in quantum information applications requires confirmation of the quantum nature of the quantum-dot-cavity system in the strong-coupling regime. Here we find such confirmation by observing quantum correlations in photoluminescence from a photonic crystal nanocavity interacting with one, and only one, quantum dot located precisely at the cavity electric field maximum. When off-resonance, photon emission from the cavity mode and quantum-dot excitons is anticorrelated at the level of single quanta, proving that the mode is driven solely by the quantum dot despite an energy mismatch between cavity and excitons. When tuned to resonance, the exciton and cavity enter the strong-coupling regime of cavity QED and the quantum-dot exciton lifetime reduces by a factor of 145. The generated photon stream becomes antibunched, proving that the strongly coupled exciton/photon system is in the quantum regime. Our observations unequivocally show that quantum information tasks are achievable in solid-state cavity QED.