Optical microcavities as platforms for entangled photon spectroscopy

Optical microcavities are often proposed as platforms for spectroscopy in the single- and few-photon regime due to strong light-matter coupling. For classical-light spectroscopies, an empty microcavity simply acts as an optical filter. However, we find that in the single- or few-photon regime treating the empty microcavity as an optical filter does not capture the full effect on the quantum state of the transmitted photons. Focusing on the case of entangled photon-pair spectroscopy, we consider how the propagation of one photon through an optical microcavity changes the joint spectrum of a frequency-entangled photon pair. Using the input-output treatment of a Dicke model, we find that propagation through a strongly coupled microcavity above a certain coupling threshold enhances the entanglement entropy between the signal and idler photons. These results show that optical microcavities are not neutral platforms for quantum-light spectroscopies and their effects must be carefully considered when using change in entanglement entropy as an observable

Measurement principles for quantum spectroscopy of molecular materials with entangled photons

Nonlinear spectroscopy with quantum entangled photons is an emerging field of research that holds the promise to achieve superior signal-to-noise ratio and effectively isolate many-body interactions. Photon sources used for this purpose, however, lack the frequency tunability and spectral bandwidth demanded by contemporary molecular materials. Here, we present design strategies for efficient spontaneous parametric downconversion to generate biphoton states with adequate spectral bandwidth and at visible wavelengths. Importantly, we demonstrate, by suitable design of the nonlinear optical interaction, the scope to engineer the degree of spectral correlations between the photons of the pair. We also present an experimental methodology to effectively characterize such spectral correlations. Importantly, we believe that such a characterization tool can be effectively adapted as a spectroscopy platform to optically probe system-bath interactions in materials.A.R.S.K. acknowledges the start-up funds provided by Wake Forest University and funding from the Center for Functional Materials and the Office of Research and Sponsored Programs at WFU. We also thank Nick Bertone from Optoelectronic Components for supplying the photon-counting units in the initial stages of this project. The authors thank Professor Carlos Silva and Professor Eric Bittner for enlightening discussions and support and Professor Daniele Faccio and Professor Matteo Clerici for providing us the Type I BBO crystal and many useful discussions on the experimental scheme. C.T. acknowledges support by European Union’s Horizon Europe (HORIZON) research and innovation programme under the Marie Sklodowska-Curie Action PIONEER (Grant Agreement 101066108). C.T. also acknowledges the Optica Foundation and Coherent Inc. for support through the Bernard J. Couillaud prize. D.O.T is supported by the PERSEPHONE project that has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 956270.Peer reviewe

Production of selenium nanoparticles occurs through an interconnected pathway of sulphur metabolism and oxidative stress response in Pseudomonas putida KT2440

The soil bacterium Pseudomonas putida KT2440 has been shown to produce selenium nanoparticles aerobically from selenite; however, the molecular actors involved in this process are unknown. Here, through a combination of genetic and analytical techniques, we report the first insights into selenite metabolism in this bacterium. Our results suggest that the reduction of selenite occurs through an interconnected metabolic network involving central metabolic reactions, sulphur metabolism, and the response to oxidative stress. Genes such as sucA, D2HGDH and PP_3148 revealed that the 2-ketoglutarate and glutamate metabolism is important to convert selenite into selenium. On the other hand, mutations affecting the activity of the sulphite reductase decreased the bacteria's ability to transform selenite. Other genes related to sulphur metabolism (ssuEF, sfnCE, sqrR, sqr and pdo2) and stress response (gqr, lsfA, ahpCF and sadI) were also identified as involved in selenite transformation. Interestingly, suppression of genes sqrR, sqr and pdo2 resulted in the production of selenium nanoparticles at a higher rate than the wild-type strain, which is of biotechnological interest. The data provided in this study brings us closer to understanding the metabolism of selenium in bacteria and offers new targets for the development of biotechnological tools for the production of selenium nanoparticles

Identidade surda e intervenções em saúde na perspectiva de uma comunidade usuária de língua de sinais Identity of the deaf and interventions in health from the perspective of a community of sign language users

A visão biomédica concebe a surdez como perda fisiológica da audição e o surdo como portador de anomalia orgânica a ser corrigida; intervenções de saúde revestem-se, correspondentemente, de tal representação. Objetivamos compreender as representações sobre surdez entre surdos, com o propósito de refletir sobre políticas públicas a eles destinadas no contexto da dimensão ética do cuidado. Utilizamos o referencial teórico-metodológico qualitativo (grupo focal); participaram 9 membros de uma comunidade surda (Fortaleza-CE, 2010) fluentes na Língua Brasileira de Sinais-Libras. Observamos que a surdez é compreendida como um modo de ser, cotidianamente construído, essencialmente a partir das experiências-vivências de interação visual com a natureza e a sociedade; assume caráter identitário particular, afirmado em componentes culturais (ser surdo) e linguísticos (Libras). Políticas públicas de oralização ou tecnologias auditivas corretivas (como o implante coclear), valorizados pela sociedade ouvinte, são representadas como retrocesso nas lutas dos surdos, de negação de seu ser no mundo e como perda da identidade surda. É necessário compreender o surdo a partir de construções histórico-sociais, simbólicas e culturais onde diferentes discursos co-existem, para além da dimensão fisiológica.<br>The biomedical view sees deafness as a physiological loss of audition and the deaf as individuals with an organic abnormality to be corrected; healthcare interventions support this perception. This study sought to understand deafness from the standpoint of the deaf, in order to identify elements for public policies addressed to them in the context of the ethical dimension of care. The research adopted the qualitative approach (focus groups) and 9 members of a deaf community in Fortaleza (Ceará-Brazil), all fluent in Brazilian Sign Language-LIBRAS, took part. The results show deafness is perceived as a way of being based on day-to-day experiences of visual interaction with nature and society, giving the deaf a different identity in terms of culture (being deaf) and linguistics (LIBRAS). Some public policies for oral training and technological interventions, like cochlear implants, are seen as a setback by the deaf, as it negates their status in the world and involves a loss of identity for the deaf. It is necessary to consider the deaf from a socio-historic, symbolic and cultural standpoint where different discourses co-exist, over and above the physiological dimension