Quantum memory for microwave photons in an inhomogeneously broadened spin ensemble

We propose a multi-mode quantum memory protocol able to store the quantum state of the field in a microwave resonator into an ensemble of electronic spins. The stored information is protected against inhomogeneous broadening of the spin ensemble by spin-echo techniques resulting in memory times orders of magnitude longer than previously achieved. By calculating the evolution of the first and second moments of the spin-cavity system variables for realistic experimental parameters, we show that a memory based on NV center spins in diamond can store a qubit encoded on the |0> and |1> Fock states of the field with 80% fidelity.Comment: 5 pages, 4 figures, 11 pages supplementary materia

Coupling a single Nitrogen-Vacancy center to a superconducting flux qubit in the far off resonance regime

We present a theoretical proposal to couple a single Nitrogen-Vacancy (NV) center to a superconducting flux qubit (FQ) in the regime where both systems are off resonance. The coupling between both quantum devices is achieved through the strong driving of the flux qubit by a classical microwave field that creates dressed states with an experimentally controlled characteristic frequency. We discuss several applications such as controlling the NV center's state by manipulation of the flux qubit, performing the NV center full tomography and using the NV center as a quantum memory. The effect of decoherence and its consequences to the proposed applications are also analyzed. Our results provide a theoretical framework describing a promising hybrid system for quantum information processing, which combines the advantages of fast manipulation and long coherence times.Comment: 8 pages, 9 figure

Efficient Algorithms on the Family Associated to an Implicational System

International audienceAn implication system (IS) on a finite set S is a set of rules called Σ -implications of the kind A →_Σ B, with A,B ⊆ S. A subset X ⊆ S satisfies A →_Σ B when ''A ⊆ X implies B ⊆ X'' holds, so ISs can be used to describe constraints on sets of elements, such as dependency or causality. ISs are formally closely linked to the well known notions of closure operators and Moore families. This paper focuses on their algorithmic aspects. A number of problems issued from an IS Σ (e.g. is it minimal, is a given implication entailed by the system) can be reduced to the computation of closures φ _Σ (X), where φ _Σ is the closure operator associated to Σ . We propose a new approach to compute such closures, based on the characterization of the direct-optimal IS Σ _do which has the following properties: \beginenumerate ıtemit is equivalent to Σ ıtemφ _Σ _do(X) (thus φ _Σ (X)) can be computed by a single scanning of Σ _do-implications ıtemit is of minimal size with respect to ISs satisfying 1. and 2. \endenumerate We give algorithms that compute Σ _do, and from Σ _do closures φ _Σ (X) and the Moore family associated to φ _Σ

The multiple facets of the canonical direct implicational basis

URL des Cahiers : https://halshs.archives-ouvertes.fr/CAHIERS-MSEVoir aussi l'article basé sur ce document de travail paru dans "Theoretical Computer Science", 2010, 411, (22-24), pp.2155-2166Cahiers de la Maison des Sciences Economiques 2005.52 - ISSN : 1624-0340Closure systems on a set S arises in many areas as relational databases, data-mining, formal concept analysis, artificial intelligence, logical programming or lattice theory. Implicational systems represents an efficient and convenient tool to deal with a closure system, and have been studied in various areas, with different terminology. This paper states the equality between five implicational systems issued from different works and satisfying various properties. The three main properties are the directness, canonical and minimality properties, thus the name canonical direct implicational basis given to this unique implicational system. This paper also gives the link between the canonical direct implicational basis and the Horn functions (via the prime implicants). It concludes by the necessity to compare more closely related works made independantly, and with different terminology in order to take advantage of the results really new.Les systèmes de fermeture (dits aussi familles de Moore) définis sur un ensemble sont présents dans de nombreux domaines de mathématiques ou d'informatique : bases de données relationnelles, fouille des données, analyse des concepts, intelligence artificielle, programmation logique ou théorie des treillis. Les systèmes d'implications sont un outil efficace pour travailler sur les systèmes de fermeture, qui a été utilisé dans la plupart de ces domaines, mais souvent avec des terminologies différentes. Nous démontrons dans ce papier l'identité de cinq systèmes d'implications étudiés dans des contextes différents et pour des propriétés variées. Les trois principales propriétés de ces systèmes sont celles d'être directs, canoniques et minimaux (d'où le nom de base canonique directe). Nous décrivons aussi le lien entre cette base directe et les fonctions de Horn (via la notion de premier impliquant d'une fonction booléenne). Nous concluons par la nécessité de comparer de façon plus approfondie des travaux faits indépendamment et sous des terminologies variées, mais en fait similaires, afin de pouvoir profiter des résultats réellement nouveaux

Critical phenomenology, aesthetics and the media “Manufacture of the guilty (Fabricaciόn de culpables)”

Ce texte est une version de travail qui peut différer de la version finale et ne doit donc pas servir aux fins de citation.La version finale de ce texte paraîtra dans Chiasmi International, no 22 (nouvelle série), sous la direction de Ted Toadvine et Corinne Lajoie, Penn State University, 2022

High-gain weakly nonlinear flux-modulated Josephson parametric amplifier using a SQUID-array

We have developed and measured a high-gain quantum-limited microwave parametric amplifier based on a superconducting lumped LC resonator with the inductor L including an array of 8 superconducting quantum interference devices (SQUIDs). This amplifier is parametrically pumped by modulating the flux threading the SQUIDs at twice the resonator frequency. Around 5 GHz, a maximum gain of 31 dB, a product amplitude-gain x bandwidth above 60 MHz, and a 1 dB compression point of -123 dBm at 20 dB gain are obtained in the non-degenerate mode of operation. Phase sensitive amplification-deamplification is also measured in the degenerate mode and yields a maximum gain of 37 dB. The compression point obtained is 18 dB above what would be obtained with a single SQUID of the same inductance, due to the smaller nonlinearity of the SQUID array.Comment: 7 pages, 4 figures, 23 reference

Detection of a persistent-current qubit by resonant activation

We present the implementation of a new scheme to detect the quantum state of a persistent-current qubit. It relies on the dependency of the measuring Superconducting Quantum Interference Device (SQUID) plasma frequency on the qubit state, which we detect by resonant activation. With a measurement pulse of only 5ns, we observed Rabi oscillations with high visibility (65%).Comment: 4 pages, 4 figures, submitted to PRB Rapid Co

The multiple facets of the canonical direct implicational basis

Closure systems on a set S arises in many areas as relational databases, data-mining, formal concept analysis, artificial intelligence, logical programming or lattice theory. Implicational systems represents an efficient and convenient tool to deal with a closure system, and have been studied in various areas, with different terminology. This paper states the equality between five implicational systems issued from different works and satisfying various properties. The three main properties are the directness, canonical and minimality properties, thus the name canonical direct implicational basis given to this unique implicational system. This paper also gives the link between the canonical direct implicational basis and the Horn functions (via the prime implicants). It concludes by the necessity to compare more closely related works made independantly, and with different terminology in order to take advantage of the results really new.Implicational system, closure operator, closure system, canonical direct basis, lattice, Horn function.

Parametric coupling for superconducting qubits

We propose a scheme to couple two superconducting charge or flux qubits biased at their symmetry points with unequal energy splittings. Modulating the coupling constant between two qubits at the sum or difference of their two frequencies allows to bring them into resonance in the rotating frame. Switching on and off the modulation amounts to switching on and off the coupling which can be realized at nanosecond speed. We discuss various physical implementations of this idea, and find that our scheme can lead to rapid operation of a two-qubit gate.Comment: 6 page