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Classification of quantum states of light using random measurements through a multimode fiber
No full textInternational audienceExtracting meaningful information about unknown quantum states without performing a full tomography is an important task. Low-dimensional projections and random measurements can provide such insight but typically require careful crafting. In this paper, we present an optical scheme based on sending unknown input states through a multimode fiber and performing two-point intensity and coincidence measurements. A short multimode fiber implements effectively a random projection in the spatial domain, while a long-dispersive multimode fiber performs a spatial and spectral projection. We experimentally show that useful properties -- i.e., the purity, dimensionality, and degree of indistinguishability -- of various states of light including spectrally entangled biphoton states, can be obtained by measuring statistical properties of photocurrents and their correlation between two outputs over many realizations of unknown random projections. Moreover, we show that this information can then be used for state classification
Observation of the diffusive Nambu-Goldstone mode of a non-equilibrium phase transition
No full textInternational audienceSecond-order phase transitions are governed by spontaneous symmetry breaking, which yield collective excitations with a gapless spectrum called Nambu-Goldstone (NG) modes. While NG modes in conservative systems are propagating excitations, non-equilibrium phase transitions have been predicted to feature a diffusive NG mode. We present the first experimental evidence of a diffusive NG mode in a non-equilibrium Bose-Einstein condensate of microcavity polaritons. The NG mode is observed as a spectral narrowing in the spectroscopic response of the condensate. Additionally, explicitly breaking the symmetry causes the opening of a gap in the spectrum and the disappearance of the NG mode. Our observations confirm the diffusive dynamics of the NG mode of non-equilibrium phase transitions and establish a promising framework to investigate fundamental questions in statistical mechanics
Exit “presentation scene”, fiat “temple entrance scene”. How to rethink this emblematic scene of the first half of the II millennium BC in light of textual records and the theory of emotions
No full textInternational audienceCan the seals from the third dynasty of Ur and Old Babylonian periods called ‘presentationscene’ seals be analyzed in a new way? And what do these seals mean? This article tries to answer these questions, starting from a detail of the seals’ iconography, the royal inscriptions and the theory of emotions
Les Chirats du Pilat: a first attempt to set chronological constraints on the formation and evolution of peculiar periglacial landforms in the eastern Central Massif
No full textInternational audienceA blockstream in geomorphology usually refers to a linear landform, aligned downs-lope, and composed of openwork, blocky, coarse rock debris that has accumulated primarilythrough mass wasting processes. These features are typically found on mountain slopes andare characterized by their elongated shape and the presence of large, angular rock blocks.They develop through the downslope movement of rock debris, supposedly by freeze-thawcycles, gravity-driven processes, and, in some cases, periglacial activity involving the possiblepresence of ice lenses within the blockstream body. Such features appear rather common inmountain and periglacial environments scattered at various latitudes worldwide. Althoughthese landforms have only received little attention in periglacial settings, recent studies con-ducted in the USA indicate that blockstreams represent dynamic, ancient, and multigener-ational landform relicts generated throughout the Pleistocene. In France, blockstreams arecommon in the eastern Central Massif (e.g., Mezenc, Pilat and Forez massifs). While theydo appear inactive today, these objects represent key witnesses of past climate and environ-mental conditions. However, no chronological constraint exists to discuss their Pleistocenedynamics and potential significance as paleo-climatic archives. Building on the analysis ofa geographic database of > 80 blockfields situated in the Pilat massif, we first draw themain morphometric characteristics of these locally called ”chirats”. We then report the first chronological constraints obtained on the Magdelaine Chirat, one major representative ofthese blockfields in the Pilat massif. We use these constraints to quantify the Pleistocene ac-tivity for the Magdelaine Chirat, using both in situ produced cosmogenic nuclides (26Al and10Be) and Schmidt hammer measurements collected on 12 rock blocks along an altitudinalgradient
: Entretien avec Richard Rechtman, anthropologue et psychiatre
No full textInternational audienceThis interview is transcribed from a workshop with Richard Rechtman that was not originally intended for publication. It addresses many questions that researchers in social sciences ask themselves during their investigation when engaging with people commonly referred to as “traumatized,” i.e., those who have experienced systemic crimes, the violence of war, death and injury, rape and torture, arrests and internment, the forced disappearance of loved ones, intense stress, and terror inflicted by the state or armed groups. The starting point of this interview is based on the need to avoid the term “trauma” and its derivatives because they mask or obscure the reality of the experience rather than helping to understand what has happened and is still happening to these individuals. Once this fundamental point has been made, numerous questions arise during the research interview. What are my limits and those of the interviewee? How can I take these intense emotions into account to go beyond the purely psychological aspects? What are the limits of the questions I can ask? Are there any? How can I protect the other and myself? How can I avoid reactivating the violence experienced during the interviews? How can I ask questions without voyeurism, or how can I position myself from an ethical point of view?Cet entretien, tiré d'un atelier avec Richard Rechtman et qui n'avait pas vocation à être publié à l'origine, aborde de très nombreuses questions que se posent chercheurs et chercheuses en sciences sociales dans le cours de leurs recherches lorsqu'ils et elles entrent en dialogue avec des personnes communément dites « traumatisées », c'est-à-dire ayant fait l'expérience de crimes systémiques, la violence de la guerre, la mort et les blessures, les viols et la torture, les arrestations et les internements, les disparitions forcées de proches, un stress intense et une terreur d'État ou de groupes armées. Le postulat de départ repose sur la nécessité d'éviter le terme de « traumatisme » et ses dérivées parce qu'ils masquent et obscurcissent la réalité de l'expérience plutôt qu'ils n'aident à penser ce qui s'est joué et se joue encore pour elles. Une fois cette remarque fondamentale posée, de nombreuses questions émaillent le travail de recherche par l'entretien. Quelles sont mes limites et celles de l’interviewé·e ? Comment prendre en compte ces émotions si vives pour en dépasser les seuls aspects psychologiques ? Quelle est la limite des questions que je peux poser ? Y en-a-t-il ? Comment préserver l’autre et se préserver soi-même ? Comment ne pas réactiver la violence vécue pendant les entretiens ? Comment questionner sans voyeurisme ou encore, comment se positionner d’un point de vue éthique
Orphée et l’orphisme dans l’émission « Tetrapharmakos – En quête du bonheur de la connaissance » de Christian Langenfeld, pour la radio Liberté FM. Diffusée le 8 avril 2025 (https://www.libertefm.fr/podcasts/tetrapharmakos-orphee-et-les-chretiens-fabienne-jourdan-5645
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Chanter pour traverser la nuit: le "Chant des cing veilles" chinois et ses usages narratifs
No full textInternational audienceSinging through the night: the Chinese ‘Song of the Five Watches’ and its narrative uses The genre known as the ‘Song of the Five Watches’ is an eminently elegiac genre of Chinese folk poetry. Covering each of the five hours of the night, it most often features a sleepless character melancholically lamenting his or her nocturnal solitude. However, these songs, whose first verse evokes twilight and whose last verse evokes the approach of dawn, are also used in plays and narrative ballads to mark the passing of the night in different ways, and have original uses in these context. We give here several examples, taken from various genres of vernacular literature: in the narrative ballad (baojuan) ‘Liu Quan Brings Melons to the Underworld’ Liu Quan jin gua, the song of the five watches serves, when it first appears, to make the audience feel the nocturnal distress of a widower, but later describes the supernatural growth of melons in a single winter night; we then turn to the Peking opera entitled ‘The Night Spent Upstairs, or the Murder of Poxi’ Zuolou sha Xi. In this play, which is part of the novel cycle Water Margin, two estranged lovers take turns singing a verse from the song of the five watches of the night to each other, expressing in turn their nostalgia for past tenderness and then the anger and disgust they now feel. The pace of the play will quicken, building to a crescendo at the moment of the crime; Finally, an unfinished song of the five watches is inserted by the narrator of the novel ‘The Magical Struggle of Yin and Yang’ Yin yang doufa zhuan to show us a mother whose son, according to a fortune teller, must die that very night. The mother, following the advice of a sorceress cries out bitterly during the first three watches of the night, calling her son. The young man, although still hours away from home, hears his mother's cries and escapes the danger threatening him at midnight. The ‘song of the five watches’ may then be interrupted and the narrator resume the prosaic course of his story.Le genre appelé « chant des cinq veilles » est un genre éminemment élégiaque de la poésie populaire chinoise. Égrenant chacune des cinq heures de la nuit, il met le plus souvent en scène un veilleur se plaignant mélancoliquement de sa solitude nocturne. Cependant, ces chants, dont le premier couplet évoque le crépuscule et le dernier l’approche de l’aube, servent aussi, dans des pièces de théâtre ou des ballades narratives, à marquer de différentes façons la traversée de la nuit et connaissent alors d’autres usages. Nous en donnons plusieurs exemples, tirés de divers genres de la littérature en langue vulgaire : la ballade narrative (baojuan) « Liu Quan apporte les melons aux enfers » Liu Quan jin gua, où le chant des cinq veilles sert, à sa première occurrence, à faire ressentir à l’auditoire la détresse nocturne d’un veuf, mais, plus loin, décrit la pousse surnaturelle de melons l’espace d’une seule nuit d’hiver ; nous abordons ensuite la pièce d’opéra de Pékin intitulée « La nuit passée à l’étage et le meurtre de Poxi » Zuolou sha Xi. Dans cette pièce, qui fait partie du cycle du roman « Au bord de l’eau », deux amants brouillés chantent chacun à son tour un couplet de la chanson des cinq veilles de la nuit à l’adresse de l’autre, exprimant successivement la nostalgie de la tendresse passée puis la colère et le dégoût qu’ils éprouvent désormais. Le rythme de la pièce s’accélèrera pour mener crescendo à l’instant du crime ; enfin, un chant des cinq veilles inachevé est inséré par le narrateur du roman « La lutte magique du yin et du yang » Yin yang doufa chuanqi pour nous montrer une mère dont le fils, doit, selon un devin, mourir cette nuit même, pousser des appels déchirants les trois premières veilles de la nuit, suivant ainsi les conseils d’une magicienne. Le jeune homme, bien qu’encore à des heures de marche de sa maison, entendra les appels de sa mère et échappera, à minuit, au danger qui le menace. Le « chant des cinq veilles » peut alors s’interrompre et le narrateur reprendre le cours prosaïque de son récit
Au Japon aussi, la neutralité des médias est au cœur des débats
No full textCroyant que son micro était éteint, un caméraman d’une grande agence de presse a laissé entendre qu’il ferait son possible pour nuire à la nouvelle cheffe du principal parti du Japon, et donc probable future première ministre. Le scandale qui s’est ensuivi a remis au premier plan une question qui existe aussi dans bien d’autres pays, à commencer par la France : celle de la neutralité des médias