Multipartite entanglement generation in coupled microcavity arrays

We consider photonic arrays made from quantum emitters in optically coupled microcavities as a platform for entanglement generation. These offer a large degree of tunability with the possibility of site-selective optical excitation. Coherent pumping is considered to drive transitions between vacuum and entangled target states both in a time-dependent manner, and in a quantum bath engineering approach to create entanglement in the steady-state. We demonstrate a numerical scheme that allows to generalize the determination of excitation parameters to larger array sizes and different classes of entangled states. This study is a step towards using coupled cavity arrays as a hardware platform in novel quantum-photonic applications in quantum computing and quantum machine learning

Aufbauender Musikunterricht vs. Musikpraxen erfahren?

Der Beitrag formuliert Gemeinsamkeiten und Unterschiede zwischen einem musikdidaktischen Konzept „Aufbauender Musikunterricht“ und einem als „Musikpraxen erfahren“ konkretisierten Konzept ästhetischer und kultureller Bildung. In vier Abschnitten werden (1) Gemeinsamkeiten, (2) Populäre Musik in „Aufbauendem Musikunterricht“ und „Musikpraxen erfahren“, (3) Musikbegriffe sowie (4) Einwände und Erwiderungen dargestellt. Im vierten Teil werden in dialogischer Form das Verhältnis von schulischen Lernsituationen und musikalischer Erfahrung, die jeweilige Normativität des musikpädagogischen Musikbegriffs, die jeweilige Sach- und Schülerorientierung, das Verhältnis von instruktiven und offenen Lehr-Lernsituationen und Konzepte für einen roten Faden im Musikunterricht reflektiert. Das jeweilige Verständnis von dem, was unter Musik verstanden wird, erweist sich als folgenreich für das musikdidaktische Konzept.The article deals with similarities and differences between a music teaching concept "Music teaching step by step" and an alternative one which is specified as a concept of aesthetic and cultural education known as "Experiencing musical practices". Topics are exposed in four sections: (1) common positions, (2) the role of popular music within "Music teaching step by step" as well as within "Experiencing musical practices", (3) what does "music" mean? and (4) objections and replies. The fourth section is presenting a dialogue, dealing with the relation between learning situations in the classroom and musical experience, as well as with the specific normativity of the music teaching concepts. Moreover, this chapter is asking, if the concepts are appropriate to the subject''s and to the pupil''s needs and if these concepts take into account the ratio of instructive teaching versus open teaching-learning situations as tools to increase the learning outcomes. The particular understanding of what we mean by "music" is seen to be crucial for music teaching concepts

Coherence properties of the two-dimensional Bose-Einstein condensate

We present a detailed finite-temperature Hartree-Fock-Bogoliubov (HFB) treatment of the two-dimensional trapped Bose gas. We highlight the numerical methods required to obtain solutions to the HFB equations within the Popov approximation, the derivation of which we outline. This method has previously been applied successfully to the three-dimensional case and we focus on the unique features of the system which are due to its reduced dimensionality. These can be found in the spectrum of low-lying excitations and in the coherence properties. We calculate the Bragg response and the coherence length within the condensate in analogy with experiments performed in the quasi-one-dimensional regime [Richard et al., Phys. Rev. Lett. 91, 010405 (2003)] and compare to results calculated for the one-dimensional case. We then make predictions for the experimental observation of the quasicondensate phase via Bragg spectroscopy in the quasi-two-dimensional regime.Comment: 9 pages, 9 figure

Gate-based protocol simulations for quantum repeaters using quantum-dot molecules in switchable electric fields

Electrically controllable quantum-dot molecules (QDMs) are a promising platform for deterministic entanglement generation and, as such, a resource for quantum-repeater networks. We develop a microscopic open-quantum-systems approach based on a time-dependent Bloch-Redfield equation to model the generation of entangled spin states with high fidelity. The state preparation is a crucial step in a protocol for deterministic entangled-photon-pair generation that we propose for quantum repeater applications. Our theory takes into account the quantum-dot molecules' electronic properties that are controlled by time-dependent electric fields as well as dissipation due to electron-phonon interaction. We quantify the transition between adiabatic and non-adiabatic regimes, which provides insights into the dynamics of adiabatic control of QDM charge states in the presence of dissipative processes. From this, we infer the maximum speed of entangled-state preparation under different experimental conditions, which serves as a first step towards simulation of attainable entangled photon-pair generation rates. The developed formalism opens the possibility for device-realistic descriptions of repeater protocol implementations.Comment: 12 pages, 11 figure