A Superconducting Laser in the Strong Coupling Regime

The present diploma work is motivated by an experiment (recently performed at NEC laboratories) on the so called "superconducting laser". It is a single-qubit laser inside a superconducting resonator driven through a Josephson quasi-particle cycle. An introduction to the properties of the \superconducting laser" requires then an introduction to the large body of work which has been performed in the last years in the eld of superconducting nano-circuits. In the introduction, we present a general description of the topic and the motivations to study it further. We also introduce the physics of Josephson junctions and brie y explain their use in quantum information and computation. We present a specic architecture for a quantum computer and explain how this all is connected to our work. Small superconducting circuits have been recognized to be very important as possible implementations of a quantum computer. Therefore part of the thesis is devoted to a description of the relation between quantum information and the physics of superconducting nano-circuits. Chapter 2 is devoted to a more quantitative description of the concepts used later in the thesis to analyse the superconducting JQP laser. We start with a brief introduction to superconductivity and present the equation of the Josephson eect, analysing the most striking behaviors of Josephson junctions. We then analyse the importance of quantum information and quantum computation, explaining which are their main tasks. To conclude the chapter, we explain how to use Josephson junctions to build superconducting qubits. With Chapter 3 we enter the main body of the thesis. Here we explain in detail the experimental setup and we describe which theoretical approaches has been used until now to explain the results. In the following chapter we generalize the master equation governing the dynamics of the superconducting laser. We overcome the hypothesis of two separate subsystems, atom and photons, when calculating the interaction of the laser with the environment. We then derive equations that explain the behavior of the laser under external pumping and in interaction with the environment. This interaction can cause decoherence and relaxation, and thus alters signicantly the output of the laser. We present the results in the Markovian and time independent regime, under the rotating wave approximation (RWA). The results obtained with this approach, along with the numerical analysis derived from the equations we found in the previous chapter, are presented in Chapter 5. We see that our results are compatible with the known small coupling results, already studied in the literature, and discuss the behavior in the new strong coupling regime. We conclude the work with a summary of the results and some hints at possible future studies

When in Rome: A Meta-corpus of Functional Harmony

‘When in Rome’ brings together all human-made, computer-encoded, functional harmonic analyses of music. This amounts in total to over 2,000 analyses of 1,500 distinct works. The most obvious motivation is scale: gathering these datasets together leads to a corpus large and varied enough for tasks including machine learning for automatic analysis, composition, and classification, as well as at-scale anthology creation and more. Further benefits include bringing together a range of different composers and genres (previous datasets typically limit themselves to one context), and of analytical perspectives on those works. We offer this data in as ready-to-use and reproducible a state as possible at http://github.com/MarkGotham/When-in-Rome, with code and documentation for all tasks reported here, including corpus conversion routines and feature extraction

A neural network for composer classification

International audienceI present a neural network approach to automatically extract musical features from 20-second audio clips in order to predict their composer. The network is composed of three convolutional layers followed by a long short-term memory recurrent layer. The model reaches an accuracy of 70% on the validation set when classifying amongst 6 composers. The work represents the early stage of a project devoted to automatic feature detection and visualization

Mechanical signatures of the current-blockade instability in suspended carbon nanotubes

Le couplage fort entre le transport électronique dans une boîte quantique à un seul niveau et un oscillateur nano-mécanique couplé capacitivement peut conduire à une transition vers un état mécaniquement bistable et bloqué en courant. Son observation est à portée de main dans les expériences de pointe menées sur les nanotubes de carbone. Nous étudions donc la réponse mécanique du système et plus précisément la fonction spectrale de déplacement, la réponse linéaire à une solicitation externe et le comportement pendant le retour à l'équilibre. Nous montrons qu'il existe une relation étroite entre les grandeurs électriques (telles le courant électrique et la fonction spectrale des fluctuations du courant) et mécaniques. Nous constatons qu'en augmentant le couplage électromécanique, les deux fonctions spectrales présentent un pic qui s'élargit et se déplace vers les basses fréquences alors que le temps de déphasage de l'oscillateur se raccourcit. Ces effets sont maximaux à la transition où les non-linéarités dominent la dynamique et sont robustes vis-à-vis de l'effet des fluctuations extérieures et de la dissipation. Ces caractéristiques fortes ouvrent la voie à la détection de la transition vers l'état de blocage du courant dans des dispositifs actuellement étudiées par plusieurs groupes.The strong coupling between electronic transport in a single-level quantum dot and a capacitively coupled nano-mechanical oscillator may lead to a transition towards a mechanically-bistable and blocked-current state. Its observation is at reach in carbonnanotube state-of-art experiments. Therefore, we investigate the mechanical response of the system, namely the displacement spectral function, the linear response to a driving, and the ring-down behavior, and the electric response, namely the electric current and current spectral function. We show that a close relation between electric and mechanical quantities exists. We find that, by increasing the lectromechanical coupling, the peak in both spectral functions broadens and shifts at low frequencies while the oscillator dephasing time shortens. These effects are maximum at the transition where nonlinearities dominate the dynamics, and are robust towards the effect of external uctuations and dissipation. These strong signatures open the way to detect the blockade transition in devices currently studied by several groups

Mechanical signatures of the current-blockade instability in suspended carbon nanotubes

Le couplage fort entre le transport électronique dans une boîte quantique à un seul niveau et un oscillateur nano-mécanique couplé capacitivement peut conduire à une transition vers un état mécaniquement bistable et bloqué en courant. Son observation est à portée de main dans les expériences de pointe menées sur les nanotubes de carbone. Nous étudions donc la réponse mécanique du système et plus précisément la fonction spectrale de déplacement, la réponse linéaire à une solicitation externe et le comportement pendant le retour à l'équilibre. Nous montrons qu'il existe une relation étroite entre les grandeurs électriques (telles le courant électrique et la fonction spectrale des fluctuations du courant) et mécaniques. Nous constatons qu'en augmentant le couplage électromécanique, les deux fonctions spectrales présentent un pic qui s'élargit et se déplace vers les basses fréquences alors que le temps de déphasage de l'oscillateur se raccourcit. Ces effets sont maximaux à la transition où les non-linéarités dominent la dynamique et sont robustes vis-à-vis de l'effet des fluctuations extérieures et de la dissipation. Ces caractéristiques fortes ouvrent la voie à la détection de la transition vers l'état de blocage du courant dans des dispositifs actuellement étudiées par plusieurs groupes.The strong coupling between electronic transport in a single-level quantum dot and a capacitively coupled nano-mechanical oscillator may lead to a transition towards a mechanically-bistable and blocked-current state. Its observation is at reach in carbonnanotube state-of-art experiments. Therefore, we investigate the mechanical response of the system, namely the displacement spectral function, the linear response to a driving, and the ring-down behavior, and the electric response, namely the electric current and current spectral function. We show that a close relation between electric and mechanical quantities exists. We find that, by increasing the lectromechanical coupling, the peak in both spectral functions broadens and shifts at low frequencies while the oscillator dephasing time shortens. These effects are maximum at the transition where nonlinearities dominate the dynamics, and are robust towards the effect of external uctuations and dissipation. These strong signatures open the way to detect the blockade transition in devices currently studied by several groups

Mechanical signatures of the current-blockade instability in suspended carbon nanotubes

Le couplage fort entre le transport électronique dans une boîte quantique à un seul niveau et un oscillateur nano-mécanique couplé capacitivement peut conduire à une transition vers un état mécaniquement bistable et bloqué en courant. Son observation est à portée de main dans les expériences de pointe menées sur les nanotubes de carbone. Nous étudions donc la réponse mécanique du système et plus précisément la fonction spectrale de déplacement, la réponse linéaire à une solicitation externe et le comportement pendant le retour à l'équilibre. Nous montrons qu'il existe une relation étroite entre les grandeurs électriques (telles le courant électrique et la fonction spectrale des fluctuations du courant) et mécaniques. Nous constatons qu'en augmentant le couplage électromécanique, les deux fonctions spectrales présentent un pic qui s'élargit et se déplace vers les basses fréquences alors que le temps de déphasage de l'oscillateur se raccourcit. Ces effets sont maximaux à la transition où les non-linéarités dominent la dynamique et sont robustes vis-à-vis de l'effet des fluctuations extérieures et de la dissipation. Ces caractéristiques fortes ouvrent la voie à la détection de la transition vers l'état de blocage du courant dans des dispositifs actuellement étudiées par plusieurs groupes.The strong coupling between electronic transport in a single-level quantum dot and a capacitively coupled nano-mechanical oscillator may lead to a transition towards a mechanically-bistable and blocked-current state. Its observation is at reach in carbonnanotube state-of-art experiments. Therefore, we investigate the mechanical response of the system, namely the displacement spectral function, the linear response to a driving, and the ring-down behavior, and the electric response, namely the electric current and current spectral function. We show that a close relation between electric and mechanical quantities exists. We find that, by increasing the lectromechanical coupling, the peak in both spectral functions broadens and shifts at low frequencies while the oscillator dephasing time shortens. These effects are maximum at the transition where nonlinearities dominate the dynamics, and are robust towards the effect of external uctuations and dissipation. These strong signatures open the way to detect the blockade transition in devices currently studied by several groups

A neural network for composer classification

International audienceI present a neural network approach to automatically extract musical features from 20-second audio clips in order to predict their composer. The network is composed of three convolutional layers followed by a long short-term memory recurrent layer. The model reaches an accuracy of 70% on the validation set when classifying amongst 6 composers. The work represents the early stage of a project devoted to automatic feature detection and visualization

A neural network for composer classification

International audienceI present a neural network approach to automatically extract musical features from 20-second audio clips in order to predict their composer. The network is composed of three convolutional layers followed by a long short-term memory recurrent layer. The model reaches an accuracy of 70% on the validation set when classifying amongst 6 composers. The work represents the early stage of a project devoted to automatic feature detection and visualization