Cavity QED with separate photon storage and qubit readout modes

We present the realization of a cavity quantum electrodynamics setup in which photons of strongly different lifetimes are engineered in different harmonic modes of the same cavity. We achieve this in a superconducting transmission line resonator with superconducting qubits coupled to the different modes. One cavity mode is strongly coupled to a detection line for qubit state readout, while a second long lifetime mode is used for photon storage and coherent quantum operations. We demonstrate sideband based measurement of photon coherence, generation of n photon Fock states and the scaling of the sideband Rabi frequency with the square root of n using a scheme that may be extended to realize sideband based two-qubit logic gates.Comment: 4 pages, 5 figures, version with high resolution figures available at http://qudev.ethz.ch/content/science/PubsPapers.htm

Off-diagonal geometric phase for mixed states

We extend the off-diagonal geometric phase [Phys. Rev. Lett. {\bf 85}, 3067 (2000)] to mixed quantal states. The nodal structure of this phase in the qubit (two-level) case is compared with that of the diagonal mixed state geometric phase [Phys. Rev. Lett. {\bf 85}, 2845 (2000)]. Extension to higher dimensional Hilbert spaces is delineated. A physical scenario for the off-diagonal mixed state geometric phase in polarization-entangled two-photon interferometry is proposed.Comment: small corrections; journal reference adde

Practical learning method for multi-scale entangled states

We describe a method for reconstructing multi-scale entangled states from a small number of efficiently-implementable measurements and fast post-processing. The method only requires single particle measurements and the total number of measurements is polynomial in the number of particles. Data post-processing for state reconstruction uses standard tools, namely matrix diagonalisation and conjugate gradient method, and scales polynomially with the number of particles. Our method prevents the build-up of errors from both numerical and experimental imperfections

Tsirelson bounds for generalized Clauser-Horne-Shimony-Holt inequalities

Quantum theory imposes a strict limit on the strength of non-local correlations. It only allows for a violation of the CHSH inequality up to the value 2 sqrt(2), known as Tsirelson's bound. In this note, we consider generalized CHSH inequalities based on many measurement settings with two possible measurement outcomes each. We demonstrate how to prove Tsirelson bounds for any such generalized CHSH inequality using semidefinite programming. As an example, we show that for any shared entangled state and observables X_1,...,X_n and Y_1,...,Y_n with eigenvalues +/- 1 we have | + <X_2 Y_1> + + + ... + - | <= 2 n cos(pi/(2n)). It is well known that there exist observables such that equality can be achieved. However, we show that these are indeed optimal. Our approach can easily be generalized to other inequalities for such observables.Comment: 9 pages, LateX, V2: Updated reference [3]. To appear in Physical Review

Учение С. Н. Шпильрейн о деструкции: теоретические и психобиографические аспекты

The article contains the characteristic of the main work in S. Spielrein’s scientific&nbsp;heritage – “Destruction as the Cause of Coming into Being” (1912). This classic&nbsp;work is considered as a scientific alternative to S. Freud’s conception ofdeath&nbsp;instinct. Freud defined the death instinct / drive as a regression,“adesire to restore&nbsp;previous condition” or “the tendency to return to the in organic state”, “to rest&nbsp;of lifeless matter”. This is consistent with his idea of “the conservative nature&nbsp;of the libido”. According to S. N. Spielrein, destruction involves thedestructionof the previous condition for the emergence of a new, destruction, providing&nbsp;transformation, “resurrection” of the individual in a new form. S. Spielrein proposes&nbsp;to distinguish between two basic instincts: the instinct of self-preservation and the&nbsp;instinct of preservation of the species. Thefirst ofthem is simple in structure and&nbsp;conservative, because it aims to preserve the individual in the state ofavailablecash. The second aims to save the species by way of constants changes, regardless&nbsp;of the individual’s selfish desires and aspirations for sustainability. The instinct&nbsp;of preservation of the species has acomplex two-component structure, in which&nbsp;erotic attraction inseparable from destruction. Thus, this instinct has ambivalent&nbsp;nature and includes both negative and positive (for ego) components.&nbsp;S. N. Spielrein’s ideas of destruction are analyzed in the context of thedestructive&nbsp;events of her life. In the article the main stages of S. Spielrein’s life are described.The author discusses her contribution to the development ofpsychoanalysis.&nbsp;The author analyzes S. N. Spielrein’s conception of destruction as an original&nbsp;attempt to integrate the ideas of C. G. Jung and S. Freud on a new theoretical&nbsp;basis.В статье приводится характеристика центральной работы в научном наследии С.&nbsp;Н.&nbsp;Шпильрейн – «Деструкция как причина становления» (1912). Эта классическая работа одного из пионеров психоанализа рассматривается как научная альтернатива концепции З.&nbsp;Фрейда о влечении к смерти. З.&nbsp;Фрейд определял влечение к смерти как регресс, «стремление к восстановлению какого-либо прежнего состояния» или «тенденцию возврата к неорганическому состоянию», «к покою неживой материи». Это вполне соответствует его идее о «консервативной природе Либидо». Согласно С.&nbsp;Н.&nbsp;Шпильрейн, деструкция предполагает уничтожение прежнего состояния ради возникновения нового, разрушение, обеспечивающее трансформацию, «воскрешение» индивида в новой форме. С.&nbsp;Шпильрейн предлагает различать два основных инстинкта: ин­стинкт самосохранения и инстинкт сохранения вида. Первый из них прост по структуре и консервативен, т.&nbsp;к. направлен на сохранение индивида в уже имеющемся наличном состоянии. Второй преследует цель сохранения рода путем постоянных изменений и новообразований, независимо от эгоистических желаний индивида и его стремления к устойчивости. Инстинкт сохранения рода имеет сложную двухкомпонентную структуру; эротическое влечение неотделимо в нем от деструкции. Таким образом, этот инстинкт амбивалентен по своей природе и включает в себя как отрицательные, так и положительные (с точки зрения Эго) компоненты. Идеи С.&nbsp;Н.&nbsp;Шпильрейн о деструкции анализируются в контексте деструктивных событий ее жизни. В статье прослеживаются этапы жизни С.&nbsp;Н.&nbsp;Шпильрейн, обсуждается ее вклад в становление психоанализа. Автор анализирует концепцию деструкции С.&nbsp;Н.&nbsp;Шпильрейн как оригинальную попытку интегрировать идеи К.&nbsp;Г.&nbsp;Юнга и З.&nbsp;Фрейда на новой теоретической основе

Using Sideband Transitions for Two-Qubit Operations in Superconducting Circuits

We demonstrate time resolved driving of two-photon blue sideband transitions between superconducting qubits and a transmission line resonator. Using the sidebands, we implement a pulse sequence that first entangles one qubit with the resonator, and subsequently distributes the entanglement between two qubits. We show generation of 75% fidelity Bell states by this method. The full density matrix of the two qubit system is extracted using joint measurement and quantum state tomography, and shows close agreement with numerical simulation. The scheme is potentially extendable to a scalable universal gate for quantum computation.Comment: 4 pages, 5 figures, version with high resolution figures available at http://qudev.ethz.ch/content/science/PubsPapers.htm

Multi-mode mediated exchange coupling in cavity QED

Microwave cavities with high quality factors enable coherent coupling of distant quantum systems. Virtual photons lead to a transverse exchange interaction between qubits, when they are non-resonant with the cavity but resonant with each other. We experimentally probe the inverse scaling of the inter-qubit coupling with the detuning from a cavity mode and its proportionality to the qubit-cavity interaction strength. We demonstrate that the enhanced coupling at higher frequencies is mediated by multiple higher-harmonic cavity modes. Moreover, in the case of resonant qubits, the symmetry properties of the system lead to an allowed two-photon transition to the doubly excited qubit state and the formation of a dark state.Comment: 9 pages, 6 figure

Suitability of Different PCR-DGGE Primer Sets for the Monitoring of Lactic Acid Bacteria in Wine

Lactic acid bacteria (LAB) play a dual role in winemaking as they are the main effectors of malolactic fermentation, but some members can also cause wine spoilage. PCR-DGGE has proved to be a quick tool to study the LAB community and their fluctuation in wine. For detecting wine-associated LAB by PCR-DGGE, the primer sets WLAB1/WLAB2GC, WBAC1/WBAC2GC, Lac1/Lac1o/Lac2GC, 341fGC/518r and rpoB1/rpoB1o/rpoB2GC were tested and evaluated in this study. The primer systems were assessed by the separation of LAB reference strains on DGGE gels and by attributing the resulting amplicons to defined species. Subsequently, the detection of LAB in wine samples and enrichments thereof was compared. While the primer systems WBAC1/WBAC2GC and 341fGC/518r were not appropriate, the Lac1/Lac1o/Lac2GC primer set performed well. However, multiple bands complicated the evaluation. The rpoB1/rpoB1o/rpoB2GC set seemed to be promising for the detection of LAB in wine, although further improvements in terms of the detection limit need to be done. Due to the pronounced sensitivity and the sufficient discrimination of LAB at species level, the WLAB1/WLAB2GC primer system was found to be most suitable for studying the occurrence of LAB in wine

Thermal Excitation of Multi-Photon Dressed States in Circuit Quantum Electrodynamics

The exceptionally strong coupling realizable between superconducting qubits and photons stored in an on-chip microwave resonator allows for the detailed study of matter-light interactions in the realm of circuit quantum electrodynamics (QED). Here we investigate the resonant interaction between a single transmon-type multilevel artificial atom and weak thermal and coherent fields. We explore up to three photon dressed states of the coupled system in a linear response heterodyne transmission measurement. The results are in good quantitative agreement with a generalized Jaynes-Cummings model. Our data indicates that the role of thermal fields in resonant cavity QED can be studied in detail using superconducting circuits.Comment: ArXiv version of manuscript to be published in the Physica Scripta topical issue on the Nobel Symposium 141: Qubits for Future Quantum Computers(2009), 13 pages, 6 figures, hi-res version at http://qudev.ethz.ch/content/science/PubsPapers.htm