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  • Enhanced Hanbury Brown and Twiss interferometry using parametric amplification
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-06-29
    Xiaoping Ma; Chenglong You; Sushovit Adhikari; Yongjian Gu; Omar S. Magaña-Loaiza; Jonathan P. Dowling; Hwang Lee

    The Hanbury Brown and Twiss (HBT) interferometer was proposed to observe intensity correlations of starlight to measure a star’s angular diameter. As the intensity of light that reaches the detector from a star is very weak, one cannot usually get a workable signal-to-noise ratio. We propose an improved HBT interferometric scheme incorporating optical parametric amplifiers (OPA) into the system to

  • Second-order effects in parametric-resonance magnetometers based on atomic alignment
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-05-07
    François Beato; Agustin Palacios-Laloy

    Optically-pumped magnetometers (OPM) based on parametric resonance allow real-time tri-axial measurement of very small magnetic fields with a single optical access to the gas cell. Most of these magnetometers rely on circularly polarized pumping light. We focus here on the ones relying on linearly polarized light, yielding atomic alignment. For these magnetometers we investigate three second order

  • A quantum key distribution protocol for rapid denial of service detection
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-05-01
    Alasdair B. Price; John G. Rarity; Chris Erven

    We introduce a quantum key distribution protocol designed to expose fake users that connect to Alice or Bob for the purpose of monopolising the link and denying service. It inherently resists attempts to exhaust Alice and Bob’s initial shared secret and is 100% efficient, regardless of the number of qubits exchanged above the finite key limit. Additionally, secure key can be generated from two-photon

  • Niobium quarter-wave resonator with the optimized shape for quantum information systems
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-04-17
    S. V. Kutsaev; K. Taletski; R. Agustsson; P. Carriere; A. N. Cleland; Z. A. Conway; É. Dumur; A. Moro; A. Yu. Smirnov

    Quantum computers (QC), if realized, could disrupt many computationally intense fields of science. The building block element of a QC is a quantum bit (qubit). Qubits enable the use of quantum superposition and multi-state entanglement in QC calculations, allowing a QC to simultaneously perform millions of computations at once. However, quantum states stored in a qubit degrade with decreased quality

  • AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-03-04
    Yousef Abou El-Neaj; Cristiano Alpigiani; Sana Amairi-Pyka; Henrique Araújo; Antun Balaž; Angelo Bassi; Lars Bathe-Peters; Baptiste Battelier; Aleksandar Belić; Elliot Bentine; José Bernabeu; Andrea Bertoldi; Robert Bingham; Diego Blas; Vasiliki Bolpasi; Kai Bongs; Sougato Bose; Philippe Bouyer; Themis Bowcock; William Bowden; Oliver Buchmueller; Clare Burrage; Xavier Calmet; Benjamin Canuel; Laurentiu-Ioan

    We propose in this White Paper a concept for a space experiment using cold atoms to search for ultra-light dark matter, and to detect gravitational waves in the frequency range between the most sensitive ranges of LISA and the terrestrial LIGO/Virgo/KAGRA/INDIGO experiments. This interdisciplinary experiment, called Atomic Experiment for Dark Matter and Gravity Exploration (AEDGE), will also complement

  • Applying the matched-filter technique to the search for dark matter transients with networks of quantum sensors
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-02-21
    Guglielmo Panelli; Benjamin M. Roberts; Andrei Derevianko

    There are several networks of precision quantum sensors in existence, including networks of atomic clocks, magnetometers, and gravitational wave detectors. These networks can be re-purposed for searches of exotic physics, such as direct dark matter searches. Here we explore a detection strategy for macroscopic dark matter objects with such networks using the matched-filter technique. Such “clumpy”

  • Scheduling of space to ground quantum key distribution
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-01-31
    Mateusz Polnik; Luca Mazzarella; Marilena Di Carlo; Daniel KL Oi; Annalisa Riccardi; Ashwin Arulselvan

    Satellite-based platforms are currently the only feasible way of achieving intercontinental range for quantum communication, enabling thus the future global quantum internet. Recent demonstrations by the Chinese spacecraft Micius have spurred an international space race and enormous interest in the development of both scientific and commercial systems. Research efforts so far have concentrated upon

  • Sensing microwave photons with a Bose–Einstein condensate
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-01-15
    Orsolya Kálmán; Peter Domokos

    We consider the interaction of a magnetically trapped Bose–Einstein condensate of Rubidium atoms with the stationary microwave radiation field sustained by a coplanar waveguide resonator. This coupling allows for the measurement of the magnetic field of the resonator by means of counting the atoms that fall out of the condensate due to hyperfine transitions to non-trapped states. We determine the quantum

  • A similarity of quantum phase transition and quench dynamics in the Dicke model beyond the thermodynamic limit
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2020-01-06
    Lituo Shen; Zhicheng Shi; Zhenbiao Yang; Huaizhi Wu; Zhirong Zhong; Shibiao Zheng

    We study the quantum phase transition in the Dicke model beyond the thermodynamic limit. With the Kibble–Zurek mechanism and adiabatic dynamics, we find that the residual energy is inversely proportional to the number of qubits, indicating that more qubits can obtain more energies from the oscillator as the number of qubits increases. Finally, we put forward a promising experiment device to realize

  • Performance analysis of an optically pumped magnetometer in Earth’s magnetic field
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2019-12-12
    Gregor Oelsner; Volkmar Schultze; Rob IJsselsteijn; Ronny Stolz

    We experimentally investigate the influence of the orientation of optically pumped magnetometers in Earth’s magnetic field. We focus our analysis to an operational mode that promises femtotesla field resolutions at such field strengths. For this so-called light-shift dispersed $M_{z}$ (LSD-Mz) regime, we focus on the key parameters defining its performance. That are the reconstructed Larmor frequency

  • Field trial of a three-state quantum key distribution scheme in the Florence metropolitan area
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2019-10-28
    Davide Bacco; Ilaria Vagniluca; Beatrice Da Lio; Nicola Biagi; Adriano Della Frera; Davide Calonico; Costanza Toninelli; Francesco S. Cataliotti; Marco Bellini; Leif K. Oxenløwe; Alessandro Zavatta

    In-field demonstrations in real-world scenarios boost the development of a rising technology towards its integration in existing infrastructures. Although quantum key distribution (QKD) devices are already adopted outside the laboratories, current field implementations still suffer from high costs and low performances, preventing this emerging technology from a large-scale deployment in telecommunication

  • Encrypted quantum correlations: delayed choice of quantum statistics and other applications
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2019-10-01
    Manuel Gessner; Augusto Smerzi

    In a three-particle extension of Wheeler’s delayed choice gedanken experiment, the quantum statistics of two particles is undetermined until a third particle is measured. As a function of the measurement result, the particles behave either as bosons or as fermions. The particles are distinguishable if no measurement is performed at all or when the measurement is performed in a rotated basis. The scheme

  • Optomechanically induced transparency and nonlinear responses based on graphene optomechanics system
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2019-08-22
    Hua-Jun Chen

    Due to its unique properties of low mass density, high frequency, high quality-factor and intrinsically small size, graphene has received significant attention and is considered as an ideal material for fabricating nanomechanical systems. In this work, we demonstrate theoretically the coherent optical propagation under different detuning regimes in the graphene resonator-microwave cavity system. In

  • Engineering cryogenic setups for 100-qubit scale superconducting circuit systems
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2019-05-28
    S. Krinner; S. Storz; P. Kurpiers; P. Magnard; J. Heinsoo; R. Keller; J. Lütolf; C. Eichler; A. Wallraff

    A robust cryogenic infrastructure in form of a wired, thermally optimized dilution refrigerator is essential for solid-state based quantum processors. Here, we engineer a cryogenic setup, which minimizes passive and active heat loads, while guaranteeing rapid qubit control and readout. We review design criteria for qubit drive lines, flux lines, and output lines used in typical experiments with superconducting

  • Finding critical states of enhanced memory capacity in attractive cold bosons.
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2019-03-25
    Gia Dvali,Marco Michel,Sebastian Zell

    We discuss a class of quantum theories which exhibit a sharply increased memory storage capacity due to emergent gapless degrees of freedom. Their realization, both theoretical and experimental, is of great interest. On the one hand, such systems are motivated from a quantum information point of view. On the other hand, they can provide a framework for simulating systems with enhanced capacity of pattern

  • Nanobob: a CubeSat mission concept for quantum communication experiments in an uplink configuration
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2018-06-22
    Erik Kerstel; Arnaud Gardelein; Mathieu Barthelemy; Matthias Fink; Siddarth Koduru Joshi; Rupert Ursin

    We present a ground-to-space quantum key distribution (QKD) mission concept and the accompanying feasibility study for the development of the associated low earth orbit nanosatellite payload. The quantum information is carried by single photons with the binary codes represented by polarization states of the photons. Distribution of entangled photons between the ground and the satellite can be used

  • Quantum simulation of Rindler transformations
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2018-05-18
    Carlos Sabín

    We show how to implement a Rindler transformation of coordinates with an embedded quantum simulator. A suitable mapping allows to realise the unphysical operation in the simulated dynamics by implementing a quantum gate on an enlarged quantum system. This enhances the versatility of embedded quantum simulators by extending the possible in-situ changes of reference frames to the non-inertial realm.

  • Q3Sat: quantum communications uplink to a 3U CubeSat—feasibility & design
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2018-04-27
    Sebastian Philipp Neumann; Siddarth Koduru Joshi; Matthias Fink; Thomas Scheidl; Roland Blach; Carsten Scharlemann; Sameh Abouagaga; Daanish Bambery; Erik Kerstel; Mathieu Barthelemy; Rupert Ursin

    Satellites are the most efficient way to achieve global scale quantum communication (Q.Com) because unavoidable losses restrict fiber based Q.Com to a few hundred kilometers. We demonstrate the feasibility of establishing a Q.Com uplink with a 3U CubeSat, measuring only 10 × 10 × 34 cm3, using commercial off-the-shelf components, the majority of which have space heritage. We demonstrate how to leverage

  • Correction to: a model study of present-day Hall-effect circulators
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2018-01-31
    B. Placke; S. Bosco; D. P. DiVincenzo

    Since the publication of the original article [Placke et al. in EPJ Quantum Technol 4:5, 2017], one of the authors noticed a typographical error to equations (11a) and (11b) in their published article [Placke et al. in EPJ Quantum Technol 4:5, 2017]. The correct versions of (11a) and (11b) are included in this Correction article. $$\begin{aligned} &C_{m}\omega_{m}= \frac{1}{\sqrt{Z_{0} R_{c}}} \sqrt{1

  • Quality factor of a transmission line coupled coplanar waveguide resonator
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2018-01-22
    Ilya Besedin; Alexey P Menushenkov

    We investigate analytically the coupling of a coplanar waveguide resonator to a coplanar waveguide feedline. Using a conformal mapping technique we obtain an expression for the characteristic mode impedances and coupling coefficients of an asymmetric multi-conductor transmission line. Leading order terms for the external quality factor and frequency shift are calculated. The obtained analytical results

  • Robust quantum state engineering through coherent localization in biased-coin quantum walks.
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2018-01-05
    Helena Majury,Joelle Boutari,Elizabeth O'Sullivan,Alessandro Ferraro,Mauro Paternostro

    We address the performance of a coin-biased quantum walk as a generator for non-classical position states of the walker. We exploit a phenomenon of coherent localization in the position space - resulting from the choice of small values of the coin parameter and assisted by post-selection - to engineer large-size coherent superpositions of position states of the walker. The protocol that we design appears

  • Laser annealing heals radiation damage in avalanche photodiodes.
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-06-07
    Jin Gyu Lim,Elena Anisimova,Brendon L Higgins,Jean-Philippe Bourgoin,Thomas Jennewein,Vadim Makarov

    Avalanche photodiodes (APDs) are a practical option for space-based quantum communications requiring single-photon detection. However, radiation damage to APDs significantly increases their dark count rates and thus reduces their useful lifetimes in orbit. We show that high-power laser annealing of irradiated APDs of three different models (Excelitas C30902SH, Excelitas SLiK, and Laser Components SAP500S2)

  • Mitigating radiation damage of single photon detectors for space applications.
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-05-26
    Elena Anisimova,Brendon L Higgins,Jean-Philippe Bourgoin,Miles Cranmer,Eric Choi,Danya Hudson,Louis P Piche,Alan Scott,Vadim Makarov,Thomas Jennewein

    Single-photon detectors in space must retain useful performance characteristics despite being bombarded with sub-atomic particles. Mitigating the effects of this space radiation is vital to enabling new space applications which require high-fidelity single-photon detection. To this end, we conducted proton radiation tests of various models of avalanche photodiodes (APDs) and one model of photomultiplier

  • JOKARUS - design of a compact optical iodine frequency reference for a sounding rocket mission
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-05-22
    Vladimir Schkolnik; Klaus Döringshoff; Franz Balthasar Gutsch; Markus Oswald; Thilo Schuldt; Claus Braxmaier; Matthias Lezius; Ronald Holzwarth; Christian Kürbis; Ahmad Bawamia; Markus Krutzik; Achim Peters

    We present the design of a compact absolute optical frequency reference for space applications based on hyperfine transitions in molecular iodine with a targeted fractional frequency instability of better than 3 × 10−14 after 1 s. It is based on a micro-integrated extended cavity diode laser with integrated optical amplifier, fiber pigtailed second harmonic generation wave-guide modules, and a quasi-monolithic

  • Characterizing the attenuation of coaxial and rectangular microwave-frequency waveguides at cryogenic temperatures.
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-05-04
    Philipp Kurpiers,Theodore Walter,Paul Magnard,Yves Salathe,Andreas Wallraff

    Low-loss waveguides are required for quantum communication at distances beyond the chip-scale for any low-temperature solid-state implementation of quantum information processors. We measure and analyze the attenuation constant of commercially available microwave-frequency waveguides down to millikelvin temperatures and single photon levels. More specifically, we characterize the frequency-dependent

  • Quantum communications and quantum metrology in the spacetime of a rotating planet.
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-04-20
    Jan Kohlrus,David Edward Bruschi,Jorma Louko,Ivette Fuentes

    We study how quantum systems that propagate in the spacetime of a rotating planet are affected by the curved background. Spacetime curvature affects wavepackets of photons propagating from Earth to a satellite, and the changes in the wavepacket encode the parameters of the spacetime. This allows us to evaluate quantitatively how quantum communications are affected by the curved spacetime background

  • A model study of present-day Hall-effect circulators
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-04-17
    B Placke; S Bosco; DP DiVincenzo

    Stimulated by the recent implementation of a three-port Hall-effect microwave circulator of Mahoney et al. (MEA), we present model studies of the performance of this device. Our calculations are based on the capacitive-coupling model of Viola and DiVincenzo (VD). Based on conductance data from a typical Hall-bar device obtained from a two-dimensional electron gas (2DEG) in a magnetic field, we numerically

  • CubeSat quantum communications mission
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-04-17
    Daniel KL Oi; Alex Ling; Giuseppe Vallone; Paolo Villoresi; Steve Greenland; Emma Kerr; Malcolm Macdonald; Harald Weinfurter; Hans Kuiper; Edoardo Charbon; Rupert Ursin

    Quantum communication is a prime space technology application and offers near-term possibilities for long-distance quantum key distribution (QKD) and experimental tests of quantum entanglement. However, there exists considerable developmental risks and subsequent costs and time required to raise the technological readiness level of terrestrial quantum technologies and to adapt them for space operations

  • Nearly optimal measurement schemes in a noisy Mach-Zehnder interferometer with coherent and squeezed vacuum
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-04-07
    Bryan T Gard; Chenglong You; Devendra K Mishra; Robinjeet Singh; Hwang Lee; Thomas R Corbitt; Jonathan P Dowling

    The use of an interferometer to perform an ultra-precise parameter estimation under noisy conditions is a challenging task. Here we discuss nearly optimal measurement schemes for a well known, sensitive input state, squeezed vacuum and coherent light. We find that a single mode intensity measurement, while the simplest and able to beat the shot-noise limit, is outperformed by other measurement schemes

  • Spatial non-adiabatic passage using geometric phases
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-03-28
    Albert Benseny; Anthony Kiely; Yongping Zhang; Thomas Busch; Andreas Ruschhaupt

    Quantum technologies based on adiabatic techniques can be highly effective, but often at the cost of being very slow. Here we introduce a set of experimentally realistic, non-adiabatic protocols for spatial state preparation, which yield the same fidelity as their adiabatic counterparts, but on fast timescales. In particular, we consider a charged particle in a system of three tunnel-coupled quantum

  • A blueprint for a simultaneous test of quantum mechanics and general relativity in a space-based quantum optics experiment
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-02-07
    Sam Pallister; Simon Coop; Valerio Formichella; Nicolas Gampierakis; Virginia Notaro; Paul Knott; Rui Azevedo; Nikolaus Buchheim; Silvio de Carvalho; Emilia Järvelä; Matthieu Laporte; Jukka-Pekka Kaikkonen; Neda Meshksar; Timo Nikkanen; Madeleine Yttergren

    In this paper we propose an experiment designed to observe a general-relativistic effect on single photon interference. The experiment consists of a folded Mach-Zehnder interferometer, with the arms distributed between a single Earth orbiter and a ground station. By compensating for other degrees of freedom and the motion of the orbiter, this setup aims to detect the influence of general relativistic

  • Reliability of analog quantum simulation
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2017-01-03
    Mohan Sarovar; Jun Zhang; Lishan Zeng

    Analog quantum simulators (AQS) will likely be the first nontrivial application of quantum technology for predictive simulation. However, there remain questions regarding the degree of confidence that can be placed in the results of AQS since they do not naturally incorporate error correction. Specifically, how do we know whether an analog simulation of a quantum model will produce predictions that

  • Geometric control theory for quantum back-action evasion
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-10-28
    Yu Yokotera; Naoki Yamamoto

    Engineering a sensor system for detecting an extremely tiny signal such as the gravitational-wave force is a very important subject in quantum physics. A major obstacle to this goal is that, in a simple detection setup, the measurement noise is lower bounded by the so-called standard quantum limit (SQL), which is originated from the intrinsic mechanical back-action noise. Hence, the sensor system has

  • Silicon nanophotonics for scalable quantum coherent feedback networks
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-10-22
    Mohan Sarovar; Daniel BS Soh; Jonathan Cox; Constantin Brif; Christopher T DeRose; Ryan Camacho; Paul Davids

    The emergence of coherent quantum feedback control (CQFC) as a new paradigm for precise manipulation of dynamics of complex quantum systems has led to the development of efficient theoretical modeling and simulation tools and opened avenues for new practical implementations. This work explores the applicability of the integrated silicon photonics platform for implementing scalable CQFC networks. If

  • 3D microwave cavity with magnetic flux control and enhanced quality factor
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-10-18
    Yarema Reshitnyk; Markus Jerger; Arkady Fedorov

    Three-dimensional (3D) microwave cavities have been extensively used for coupling and interacting with superconducting quantum bits (qubits), providing a versatile platform for quantum control experiments and for realizing hybrid quantum systems. While having high quality factors (>106) superconducting cavities do not permit magnetic field control of qubits. In contrast, cavities made of normal metals

  • Nanosatellite experiments to enable future space-based QKD missions
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-10-18
    Robert Bedington; Xueliang Bai; Edward Truong-Cao; Yue Chuan Tan; Kadir Durak; Aitor Villar Zafra; James A Grieve; Daniel KL Oi; Alexander Ling

    We present a programme for establishing the space worthiness of highly-miniaturised, polarisation-entangled, photon pair sources using CubeSat nanosatellites. Once demonstrated, the photon pair sources can be deployed on more advanced satellites that are equipped with optical links to establish a global space-based quantum key distribution network. In doing so, this work will also bring experimental

  • Few-qubit quantum-classical simulation of strongly correlated lattice fermions
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-08-08
    Juha M Kreula; Laura García-Álvarez; Lucas Lamata; Stephen R Clark; Enrique Solano; Dieter Jaksch

    We study a proof-of-principle example of the recently proposed hybrid quantum-classical simulation of strongly correlated fermion models in the thermodynamic limit. In a ‘two-site’ dynamical mean-field theory (DMFT) approach we reduce the Hubbard model to an effective impurity model subject to self-consistency conditions. The resulting minimal two-site representation of the non-linear hybrid setup

  • Tunable coupling of transmission-line microwave resonators mediated by an rf SQUID
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-07-28
    Friedrich Wulschner; Jan Goetz; Fabian R Koessel; Elisabeth Hoffmann; Alexander Baust; Peter Eder; Michael Fischer; Max Haeberlein; Manuel J Schwarz; Matthias Pernpeintner; Edwar Xie; Ling Zhong; Christoph W Zollitsch; Borja Peropadre; Juan-Jose Garcia Ripoll; Enrique Solano; Kirill G Fedorov; Edwin P Menzel; Frank Deppe; Achim Marx; Rudolf Gross

    We realize tunable coupling between two superconducting transmission line resonators. The coupling is mediated by a non-hysteretic rf SQUID acting as a flux-tunable mutual inductance between the resonators. We present a spectroscopic characterization of the device. In particular, we observe couplings $g/2\pi$ ranging between −320 MHz and 37 MHz. In the case of $g \simeq 0$ , the microwave power cross

  • Quantum simulation of the Anderson Hamiltonian with an array of coupled nanoresonators: delocalization and thermalization effects
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-06-08
    John Lozada-Vera; Alejandro Carrillo; Olimpio P de Sá Neto; Jalil K Moqadam; Matthew D LaHaye; Marcos C de Oliveira

    The possibility of using nanoelectromechanical systems as a simulation tool for quantum many-body effects is explored. It is demonstrated that an array of electrostatically coupled nanoresonators can effectively simulate the Bose-Hubbard model without interactions, corresponding in the single-phonon regime to the Anderson tight-binding model. Employing a density matrix formalism for the system coupled

  • Thermal noise in BEC-phononic gravitational wave detectors
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-05-20
    Carlos Sabín; Jan Kohlrus; David Edward Bruschi; Ivette Fuentes

    Quasiparticles in a Bose-Einstein condensate are sensitive to space-time distortions. Gravitational waves can induce transformations on the state of phonons that can be observed through quantum state discrimination techniques. We show that this method is highly robust to thermal noise and depletion. We derive a bound on the strain sensitivity that shows that the detection of waves in the kHz regime

  • Quantum interferences reconstruction with low homodyne detection efficiency
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-05-04
    Martina Esposito; Francesco Randi; Kelvin Titimbo; Georgios Kourousias; Alessio Curri; Roberto Floreanini; Fulvio Parmigiani; Daniele Fausti; Klaus Zimmermann; Fabio Benatti

    Optical homodyne tomography consists in reconstructing the quantum state of an optical field from repeated measurements of its amplitude at different field phases (homodyne data). The experimental noise, which unavoidably affects the homodyne data, leads to a detection efficiency $\eta<1$ . The problem of reconstructing quantum states from noisy homodyne data sets prompted an intense scientific debate

  • Multi-qubit joint measurements in circuit QED: stochastic master equation analysis
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-04-04
    Ben Criger; Alessandro Ciani; David P DiVincenzo

    We derive a family of stochastic master equations describing homodyne measurement of multi-qubit diagonal observables in circuit quantum electrodynamics. In the regime where qubit decay can be neglected, our approach replaces the polaron-like transformation of previous work, which required a lengthy calculation for the physically interesting case of three qubits and two resonator modes. The technique

  • Macroscopic Quantum Resonators (MAQRO): 2015 update
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-03-24
    Rainer Kaltenbaek; Markus Aspelmeyer; Peter F Barker; Angelo Bassi; James Bateman; Kai Bongs; Sougato Bose; Claus Braxmaier; Časlav Brukner; Bruno Christophe; Michael Chwalla; Pierre-François Cohadon; Adrian Michael Cruise; Catalina Curceanu; Kishan Dholakia; Lajos Diósi; Klaus Döringshoff; Wolfgang Ertmer; Jan Gieseler; Norman Gürlebeck; Gerald Hechenblaikner; Antoine Heidmann; Sven Herrmann; Sabine

    Do the laws of quantum physics still hold for macroscopic objects - this is at the heart of Schrödinger’s cat paradox - or do gravitation or yet unknown effects set a limit for massive particles? What is the fundamental relation between quantum physics and gravity? Ground-based experiments addressing these questions may soon face limitations due to limited free-fall times and the quality of vacuum

  • Methodology for bus layout for topological quantum error correcting codes
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-03-09
    Martin Wosnitzka; Fabio L Pedrocchi; David P DiVincenzo

    Most quantum computing architectures can be realized as two-dimensional lattices of qubits that interact with each other. We take transmon qubits and transmission line resonators as promising candidates for qubits and couplers; we use them as basic building elements of a quantum code. We then propose a simple framework to determine the optimal experimental layout to realize quantum codes. We show that

  • Trapped modes in linear quantum stochastic networks with delays
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-03-03
    Gil Tabak; Hideo Mabuchi

    Networks of open quantum systems with feedback have become an active area of research for applications such as quantum control, quantum communication and coherent information processing. A canonical formalism for the interconnection of open quantum systems using quantum stochastic differential equations (QSDEs) has been developed by Gough, James and co-workers and has been used to develop practical

  • Quantum metamaterials in the microwave and optical ranges
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-02-20
    Alexandre M Zagoskin; Didier Felbacq; Emmanuel Rousseau

    Quantum metamaterials generalize the concept of metamaterials (artificial optical media) to the case when their optical properties are determined by the interplay of quantum effects in the constituent ‘artificial atoms’ with the electromagnetic field modes in the system. The theoretical investigation of these structures demonstrated that a number of new effects (such as quantum birefringence, strongly

  • Dynamical nuclear polarization using multi-colour control of color centers in diamond
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2016-01-13
    Pengcheng Yang; Martin B Plenio; Jianming Cai

    Dynamical nuclear polarization (DNP) transfers the polarization of electron spins at cryogenic temperatures to achieve strong nuclear polarization for applications in nuclear magnetic resonance. Recently introduced approaches employ optical pumping of nitrogen-vacancy (NV) centers in diamond to achieve DNP even at ambient temperatures. In such schemes microwave radiation is used to establish a Hartmann-Hahn

  • Quantum teleportation of propagating quantum microwaves
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2015-12-15
    R Di Candia; KG Fedorov; L Zhong; S Felicetti; EP Menzel; M Sanz; F Deppe; A Marx; R Gross; E Solano

    Propagating quantum microwaves have been proposed and successfully implemented to generate entanglement, thereby establishing a promising platform for the realisation of a quantum communication channel. However, the implementation of quantum teleportation with photons in the microwave regime is still absent. At the same time, recent developments in the field show that this key protocol could be feasible

  • Interpolation approach to Hamiltonian-varying quantum systems and the adiabatic theorem
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2015-11-25
    Yu Pan; Zibo Miao; Nina H Amini; Valery Ugrinovskii; Matthew R James

    Quantum control could be implemented by varying the system Hamiltonian. According to adiabatic theorem, a slowly changing Hamiltonian can approximately keep the system at the ground state during the evolution if the initial state is a ground state. In this paper we consider this process as an interpolation between the initial and final Hamiltonians. We use the mean value of a single operator to measure

  • Neutral impurities in a Bose-Einstein condensate for simulation of the Fröhlich-polaron
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2015-11-14
    Michael Hohmann; Farina Kindermann; Benjamin Gänger; Tobias Lausch; Daniel Mayer; Felix Schmidt; Artur Widera

    We present an experimental system to study the Bose polaron by immersion of single, well-controllable neutral Cs impurities into a Rb Bose-Einstein condensate (BEC). We show that, by proper optical traps, independent control over impurity and BEC allows for precision relative positioning of the two sub-systems as well as for dynamical studies and independent read-out. We furthermore estimate that measuring

  • Longitudinal spin relaxation in nitrogen-vacancy ensembles in diamond
    EPJ Quantum Technol. (IF 3.0) Pub Date : 2015-10-29
    Mariusz Mrózek; Daniel Rudnicki; Pauli Kehayias; Andrey Jarmola; Dmitry Budker; Wojciech Gawlik

    We present an experimental study of the longitudinal electron-spin relaxation of ensembles of negatively charged nitrogen-vacancy (NV−) centers in diamond. The measurements were performed with samples having different NV− concentrations and at different temperatures and magnetic fields. We found that the relaxation rate $T_{1}^{-1}$ increases when transition frequencies in NV− centers with different

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