Results for "Christoph Simon"

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Conscious observers clarify many worldsAug 03 2009In this brief note I argue that putting conscious observers at the center of the considerations clarifies and strengthens the many-worlds interpretation. The basic assumption, which seems extremely plausible based on our current understanding of the brain ... More
Towards a global quantum networkOct 31 2017The creation of a global quantum network is within reach combining satellite links and quantum memory based approaches. Applications will range from secure communication and fundamental physics experiments to a future quantum internet.
Natural Entanglement in Bose-Einstein CondensatesOct 18 2001Every Bose-Einstein condensate is in a highly entangled state, as a consequence of the fact that the particles in a condensate are distributed over space in a coherent way. It is proved that any two regions within a condensate of finite particle number ... More
Comment on "Separability of quantum states and the violation of Bell-type inequalities"Oct 05 2004The statement of E.R. Loubenets, Phys. Rev. A 69, 042102 (2004), that separable states can violate classical probabilistic constraints is based on a misleading definition of classicality, which is much narrower than Bell's concept of local hidden variables. ... More
The Foundations of Quantum Information and Feasible ExperimentsMar 12 2001This thesis consists of four parts. In the first part it is shown that optimal universal cloning of photons can be realized with the help of stimulated emission. Possible schemes based on three-level systems and on parametric down-conversion are analyzed ... More
Could Energy Decoherence due to Quantum Gravity be observed?Jun 01 2004It has recently been proposed that quantum gravity might lead to the decoherence of superpositions in energy, corresponding to a discretization of time at the Planck scale. At first sight the proposal seems amenable to experimental verification with methods ... More
Robustness of Multi-Party EntanglementSep 20 2001How common is large-scale entanglement in nature? As a first step towards addressing this question, we study the robustness of multi-party entanglement under local decoherence, modeled by partially depolarizing channels acting independently on each subsystem. ... More
Proposal to demonstrate the non-locality of Bohmian mechanics with entangled photonsJul 11 2012Bohmian mechanics reproduces all statistical predictions of quantum mechanics, which ensures that entanglement cannot be used for superluminal signaling. However, individual Bohmian particles can experience superluminal influences. We propose to illustrate ... More
Measuring small longitudinal phase shifts: weak measurements or standard interferometry?Nov 26 2009Jul 09 2010Recently, weak measurements were used to measure small effects that are transverse to the propagation direction of a light beam. Here we address the question whether weak measurements are also useful for measuring small longitudinal phase shifts. We show ... More
Precision of single-qubit gates based on Raman transitionsOct 03 2005We analyze the achievable precision for single-qubit gates that are based on Raman transitions between two near-degenerate ground states via a virtually excited state. In particular, we study the errors due to non-perfect adiabaticity and due to spontaneous ... More
Theory of an Entanglement LaserFeb 03 2003We consider the creation of polarization entangled light from parametric down- conversion driven by an intense pulsed pump inside a cavity. The multi-photon states produced are close approximations to singlet states of two very large spins. A criterion ... More
Impedance-matched cavity quantum memoryApr 14 2010We consider an atomic frequency comb based quantum memory inside an asymmetric optical cavity. In this configuration it is possible to absorb the input light completely in a system with an effective optical depth of one, provided that the absorption per ... More
Integer Vector Addition Systems with StatesJun 10 2014Jul 28 2014This paper studies reachability, coverability and inclusion problems for Integer Vector Addition Systems with States (ZVASS) and extensions and restrictions thereof. A ZVASS comprises a finite-state controller with a finite number of counters ranging ... More
Multi-Partite Entanglement Inequalities via Spin Vector GeometryApr 11 2005Oct 25 2005We introduce inequalities for multi-partite entanglement, derived from the geometry of spin vectors. The criteria are constructed iteratively from cross and dot products between the spins of individual subsystems, each of which may have arbitrary dimension. ... More
Creating single time-bin entangled photon pairsSep 16 2004When a single emitter is excited by two phase-coherent pulses with a time delay, each of the pulses can lead to the emission of a photon pair, thus creating a ``time-bin entangled'' state. Double pair emission can be avoided by initially preparing the ... More
Polarization Entanglement Purification using Spatial EntanglementAug 13 2001Parametric down-conversion can produce photons that are entangled both in polarization and in space. Here we show how the spatial entanglement can be used to purify the polarization entanglement using only linear optical elements. Spatial entanglement ... More
Fock-state view of weak-value measurements and implementation with photons and atomic ensemblesOct 18 2010Weak measurements in combination with post-selection can give rise to a striking amplification effect (related to a large "weak value"). We show that this effect can be understood by viewing the initial state of the pointer as the ground state of a fictional ... More
An implementation of Deflate in CoqSep 05 2016The widely-used compression format "Deflate" is defined in RFC 1951 and is based on prefix-free codings and backreferences. There are unclear points about the way these codings are specified, and several sources for confusion in the standard. We tried ... More
Photon-photon gate via the interaction between two collective Rydberg excitationsJul 28 2014We propose a scheme for a deterministic controlled-phase gate between two photons based on the strong interaction between two stationary collective Rydberg excitations in an atomic ensemble. The distance-dependent character of the interaction causes both ... More
Robust long-distance entanglement and a loophole-free Bell test with ions and photonsMar 05 2003Feb 18 2004Two trapped ions that are kilometers apart can be entangled by the joint detection of two photons, each coming from one of the ions, in a basis of entangled states. Such a detection is possible with linear optical elements. The use of two-photon interference ... More
Context-Free Commutative Grammars with Integer Counters and ResetsNov 16 2015Jun 24 2016We study the computational complexity of reachability, coverability and inclusion for extensions of context-free commutative grammars with integer counters and reset operations on them. Those grammars can alternatively be viewed as an extension of communication-free ... More
On the quantification of entanglement in infinite-dimensional quantum systemsDec 11 2001Apr 03 2002We investigate entanglement measures in the infinite-dimensional regime. First, we discuss the peculiarities that may occur if the Hilbert space of a bi-partite system is infinite-dimensional, most notably the fact that the set of states with infinite ... More
The no-signaling condition and quantum dynamicsFeb 23 2001We show that the basic dynamical rules of quantum physics can be derived from its static properties and the condition that superluminal communication is forbidden. More precisely, the fact that the dynamics has to be described by linear completely positive ... More
Multi-Photon Entanglement Concentration and Quantum CryptographySep 26 2001Jun 05 2002Multi-photon states from parametric down-conversion can be entangled both in polarization and photon number. Maximal high-dimensional entanglement can be concentrated from these states via photon counting. This makes them natural candidates for quantum ... More
Single-photon source based on Rydberg exciton blockadeFeb 04 2017We propose to implement a new kind of solid-state single-photon source based on the recently observed Rydberg blockade effect for excitons in cuprous oxide. The strong interaction between excitons in levels with high principal quantum numbers prevents ... More
Chimera patterns in conservative systems and ultracold atoms with mediated nonlocal hoppingAug 15 2017Chimera patterns, characterized by coexisting regions of phase coherence and incoherence, have so far been studied in non-conservative systems with dissipation. Here, we show that the formation of chimera patterns can also be observed in conservative ... More
Temporally multiplexed quantum repeaters with atomic gasesJul 28 2010We propose a temporally multiplexed version of the Duan-Lukin-Cirac-Zoller (DLCZ) quantum repeater protocol using controlled inhomogeneous spin broadening in atomic gases. A first analysis suggests that the advantage of multiplexing is negated by noise ... More
Proposal for Inverting the Quantum Cloning of PhotonsNov 30 2011Mar 23 2012We propose an experiment where a photon is first cloned by stimulated parametric down-conversion, making many (imperfect) copies, and then the cloning transformation is inverted, regenerating the original photon while destroying the copies. Focusing on ... More
Cross-Kerr nonlinearity between continuous-mode coherent states and single photonsFeb 18 2011Mar 07 2011Weak cross-Kerr nonlinearities between single photons and coherent states are the basis for many applications in quantum information processing. These nonlinearities have so far mainly been discussed in terms of highly idealized single-mode models. We ... More
Photonic quantum memory in two-level ensembles based on modulating the refractive index in time: equivalence to gradient echo memoryMay 23 2012We present a quantum memory protocol that allows to store light in ensembles of two-level atoms, e.g. rare-earth ions doped into a crystal, by modulating the refractive index of the host medium of the atoms linearly in time. We show that under certain ... More
Hidden-variable theorems for real experimentsJun 08 2000Mar 28 2001It has recently been questioned whether the Kochen-Specker theorem is relevant to real experiments, which by necessity only have finite precision. We give an affirmative answer to this question by showing how to derive hidden-variable theorems that apply ... More
Lambda's, V's and optimal cloning with stimulated emissionMar 07 2000We show that optimal universal cloning of the polarization state of photons can be achieved via stimulated emission in three-level systems, both of the Lambda and the V type. We establish the equivalence of our systems with coupled harmonic oscillators, ... More
On Global Solutions for Quasilinear One-Dimensional Parabolic Problems with Dynamical Boundary ConditionsMay 01 2015We provide sufficient and almost optimal conditions for global existence of classical solutions in parabolic H\"older spaces to quasilinear one-dimensional parabolic problems with dynamical boundary conditions.
Focus on Quantum MemoriesApr 10 2015Quantum memories are essential for quantum information processing and long-distance quantum communication. The field has recently seen a lot of progress, and the present focus issue offers a glimpse of these developments, showing both experimental and ... More
Optimal curvature estimates for homogeneous Ricci flowsApr 10 2016Jun 01 2016We prove uniform curvature estimates for homogeneous Ricci flows: For a solution defined on $[0,t]$ the norm of the curvature tensor at time $t$ is bounded by the maximum of $C(n)/t$ and $C(n) ( scal(g(t)) - scal(g(0)) )$. This is used to show that solutions ... More
Partially dualized Hopf algebras have equivalent Yetter-Drinfel'd modulesFeb 10 2014Given a Hopf algebra $H$ and a projection $H\to A$ to a Hopf subalgebra, we construct a Hopf algebra $r(H)$, called the partial dualization of $H$, with a projection to the Hopf algebra dual to $A$. This construction provides powerful techniques in the ... More
Creating and detecting micro-macro photon-number entanglement by amplifying and de-amplifying a single-photon entangled stateOct 04 2012We propose a scheme for the observation of micro-macro entanglement in photon number based on amplifying and de-amplifying a single-photon entangled state in combination with homodyne quantum state tomography. The created micro-macro entangled state, ... More
Demonstrating macroscopic entanglement based on Kerr non-linearities requires extreme phase resolutionJun 16 2012Entangled coherent states, which can in principle be created using strong Kerr non-linearities, allow the violation of Bell inequalities for very coarse-grained measurements. This seems to contradict a recent conjecture that observing quantum effects ... More
Coarse Graining Makes It Hard to See Micro-Macro EntanglementAug 09 2011Feb 19 2012Observing quantum effects such as superpositions and entanglement in macroscopic systems requires not only a system that is well protected against environmental decoherence, but also sufficient measurement precision. Motivated by recent experiments, we ... More
Heralded amplification for precision measurements with spin ensemblesJul 14 2011We propose a simple heralded amplification scheme for small rotations of the collective spin of an ensemble of particles. Our protocol makes use of two basic primitives for quantum memories, namely partial mapping of light onto an ensemble, and conversion ... More
Optimal Quantum Cloning via Stimulated EmissionOct 12 1999We show that optimal universal quantum cloning can be realized via stimulated emission. Universality of the cloning procedure is achieved by choosing systems that have appropriate symmetries. We first discuss a scheme based on stimulated emission in certain ... More
Quantum Cryptography with Entangled PhotonsDec 28 1999By realizing a quantum cryptography system based on polarization entangled photon pairs we establish highly secure keys, because a single photon source is approximated and the inherent randomness of quantum measurements is exploited. We implement a novel ... More
Purification of single-photon entanglement with linear opticsNov 18 2008We show that single-photon entangled states of the form |0>|1>+|1>|0> can be purified with a simple linear-optics based protocol, which is eminently feasible with current technology. Besides its conceptual interest, this result is relevant for attractive ... More
Why the two-pulse photon echo is not a good quantum memory protocolOct 03 2008We consider in this paper a two-pulse photon echo sequence as a potential quantum light storage protocol. It is widely believed that a two-pulse scheme should lead to very low efficiency and is then not relevant for this specific application. We show ... More
Multimode quantum memory based on atomic frequency combsMay 27 2008May 22 2009An efficient multi-mode quantum memory is a crucial resource for long-distance quantum communication based on quantum repeaters. We propose a quantum memory based on spectral shaping of an inhomogeneously broadened optical transition into an atomic frequency ... More
A feasible "Kochen-Specker" experiment with single particlesSep 19 2000We present a simple experimental scheme which can be used to demonstrate an all-or-nothing type contradiction between non-contextual hidden variables and quantum mechanics. The scheme, which is inspired by recent ideas by Cabello and Garcia-Alcaine, shows ... More
Hochschild Cohomology and the Modular GroupJul 13 2017It has been shown in previous work that the modular group acts projectively on the center of a factorizable ribbon Hopf algebra. The center is the zeroth Hochschild cohomology group. In this article, we extend this projective action of the modular group ... More
Cloning Entangled Qubits to Scales One Can SeeMay 27 2010By amplifying photonic qubits it is possible to produce states that contain enough photons to be seen with a human eye, potentially bringing quantum effects to macroscopic scales [1]. In this paper we theoretically study quantum states obtained by amplifying ... More
Quantum experiments with human eyes as detectors based on cloning via stimulated emissionFeb 17 2009We show theoretically that the multi-photon states obtained by cloning single-photon qubits via stimulated emission can be distinguished with the naked human eye with high efficiency and fidelity. Focusing on the "micro-macro" situation realized in a ... More
Are there optical communication channels in the brain?Aug 23 2017Despite great progress in neuroscience, there are still fundamental unanswered questions about the brain, including the origin of subjective experience and consciousness. Some answers might rely on new physical mechanisms. Given that biophotons have been ... More
Towards a Room-Temperature Spin-Photon Interface based on Nitrogen-Vacancy centers and OptomechanicsNov 06 2017The implementation of quantum networks involving quantum memories and photonic channels without the need for cryogenics would be a major technological breakthrough. Nitrogen-vacancy centers have excellent spin properties even at room temperature, but ... More
Coherent frequency-down-conversion interface for quantum repeatersJun 23 2010Oct 13 2010We report a coherence-preserving photon frequency down-conversion experiment based on difference-frequency generation in a periodically poled Lithium niobate waveguide, at the single-photon level. The coherence of the process has been demonstrated by ... More
Detection loophole in asymmetric Bell experimentsFeb 13 2007Feb 21 2007The problem of closing the detection loophole with asymmetric systems, such as entangled atom-photon pairs, is addressed. We show that, for the Bell inequality I_3322, a minimal detection efficiency of 43% can be tolerated for one of the particles, if ... More
Analysis of a quantum memory for photons based on controlled reversible inhomogeneous broadeningNov 15 2006Jan 30 2007We present a detailed analysis of a quantum memory for photons based on controlled and reversible inhomogeneous broadening (CRIB). The explicit solution of the equations of motion is obtained in the weak excitation regime, making it possible to gain insight ... More
Towards room temperature indistinguishable single-photon sources using ultra-small mode volume cavities and solid-state emittersOct 10 2017Efficient sources of indistinguishable single photons that can operate at room temperature would be highly beneficial for many applications in quantum technology. We show that the implementation of such sources is a realistic goal using solid-state emitters ... More
Advanced tools for smartphone-based experiments: phyphoxApr 17 2018The sensors in modern smartphones are a promising and cost-effective tool for experimentation in physics education, but many experiments face practical problems. Often the phone is inaccessible during the experiment and the data usually needs to be analyzed ... More
Fully Quantum Approach to Optomechanical EntanglementAug 27 2013Aug 12 2014The radiation pressure induced coupling between an optical cavity field and a mechanical oscillator can create entanglement between them. In previous works this entanglement was treated as that of the quantum fluctuations of the cavity and mechanical ... More
Can coarse measurements reveal macroscopic quantum effects?Jul 02 2013It has recently been conjectured that detecting quantum effects such as superposition or entanglement for macroscopic systems always requires high measurement precision. Analyzing an apparent counter-example involving macroscopic coherent states and Kerr ... More
Quantum repeaters based on atomic ensembles and linear opticsJun 15 2009Jun 23 2009The distribution of quantum states over long distances is limited by photon loss. Straightforward amplification as in classical telecommunications is not an option in quantum communication because of the no-cloning theorem. This problem could be overcome ... More
Violation of Bell's inequality under strict Einstein locality conditionsOct 26 1998We observe strong violation of Bell's inequality in an Einstein, Podolsky and Rosen type experiment with independent observers. Our experiment definitely implements the ideas behind the well known work by Aspect et al. We for the first time fully enforce ... More
Macroscopic superpositions via nested interferometry: finite temperature and decoherence considerationsJul 09 2012Recently there has been much interest in optomechanical devices for the production of macroscopic quantum states. Here we focus on a proposed scheme for achieving macroscopic superpositions via nested interferometry. We consider the effects of finite ... More
Experimental Quantum Cloning of Single PhotonsMay 23 2002Although perfect copying of unknown quantum systems is forbidden by the laws of quantum mechanics, approximate cloning is possible. A natural way of realizing quantum cloning of photons is by stimulated emission. In this context the fundamental quantum ... More
Preference-based TeachingFeb 06 2017Feb 08 2017We introduce a new model of teaching named "preference-based teaching" and a corresponding complexity parameter---the preference-based teaching dimension (PBTD)---representing the worst-case number of examples needed to teach any concept in a given concept ... More
Non-destructive photon detection using a single rare earth ion coupled to a photonic cavityAug 24 2016We study the possibility of using single rare-earth ions coupled to a photonic cavity with high cooperativity for performing non-destructive measurements of photons, which would be useful for global quantum networks and photonic quantum computing. We ... More
Binary Mixtures of Particles with Different Diffusivities DemixMay 04 2015Feb 14 2016The influence of size differences, shape, mass and persistent motion on phase separation in binary mixtures has been intensively studied. Here we focus on the exclusive role of diffusivity differences in binary mixtures of equal-sized particles. We find ... More
Collision dynamics and entanglement generation of two initially independent and indistinguishable boson pairs in one-dimensional harmonic confinementMar 06 2013We investigate finite number effects in collisions between two states of an initially well known number of identical bosons with contact interactions, oscillating in the presence of harmonic confinement in one dimension. We investigate two N/2 (interacting) ... More
Quantum theory of bright matter wave solitons in harmonic confinementMar 27 2012May 14 2012This paper investigates bright quantum-matter-wave solitons beyond the Gross-Pitaevskii equation (GPE). As proposals for interferometry and creating nonlocal quantum superpositions have been formed, it has become necessary to investigate effects not present ... More
Towards quantum superpositions of a mirrorSep 30 2002We propose a scheme for creating quantum superposition states involving of order $10^{14}$ atoms via the interaction of a single photon with a tiny mirror. This mirror, mounted on a high-quality mechanical oscillator, is part of a high-finesse optical ... More
Optomechanical superpositions via nested interferometryNov 24 2011Apr 03 2012We present a scheme for achieving macroscopic quantum superpositions in optomechanical systems by using single photon postselection and detecting them with nested interferometers. This method relieves many of the challenges associated with previous optical ... More
Feasible Entanglement Purification for Quantum CommunicationDec 05 2000The distribution of entangled states between distant locations will be essential for the future large scale realization of quantum communication schemes such as quantum cryptography and quantum teleportation. Because of the unavoidable noise in the quantum ... More
Simple time-of-flight measurement of the speed of sound using smartphonesApr 17 2018We propose an easy experiment that allows to determine the speed of sound through a simple time-of-flight measurement using two smartphones
Superballistic center-of-mass motion in one-dimensional attractive Bose gases: Decoherence-induced Gaussian random walks in velocity spaceOct 18 2015We show that the center-of-mass motion of ultracold attractively interacting bosons can become superballistic in the presence of decoherence, via single-, two- and/or three-body losses. In the limit of weak decoherence, we analytically solve the numerical ... More
Modeling H2 formation in the turbulent ISM: Solenoidal versus compressive turbulent forcingMar 15 2011Dec 30 2011We present results from high-resolution three-dimensional simulations of the turbulent interstellar medium that study the influence of the nature of the turbulence on the formation of molecular hydrogen. We have examined both solenoidal (divergence-free) ... More
Entangling two distinguishable quantum bright solitons via collisionsJan 03 2014The generation of mesoscopic Bell states via collisions of distinguishable bright solitons has been suggested in Phys. Rev. Lett. 111, 100406 (2013). Here, we extend our former proposal to two hyperfine states of 85Rb instead of two different atomic species, ... More
Electric control of collective atomic coherence in an Erbium doped solidJul 14 2009Jul 24 2009We demonstrate fast and accurate control of the evolution of collective atomic coherences in an Erbium doped solid using external electric fields. This is achieved by controlling the inhomogeneous broadening of Erbium ions emitting at 1536 nm using an ... More
Quantum Repeaters with Photon Pair Sources and Multi-Mode MemoriesJan 31 2007Apr 05 2007We propose a quantum repeater protocol which builds on the well-known DLCZ protocol [L.M. Duan, M.D. Lukin, J.I. Cirac, and P. Zoller, Nature 414, 413 (2001)], but which uses photon pair sources in combination with memories that allow to store a large ... More
Quantum Communication with Quantum Dot SpinsSep 05 2006Nov 24 2006Single electron spins in quantum dots are attractive for quantum communication because of their expected long coherence times. We propose a method to create entanglement between two remote spins based on the coincident detection of two photons emitted ... More
Quantum Storage and Retrieval of Light by Sweeping the Atomic FrequencyApr 11 2013We propose a quantum memory protocol based on dynamically changing the resonance frequency of an ensemble of two-level atoms. By sweeping the atomic frequency in an adiabatic fashion, photons are reversibly transferred into atomic coherences. We present ... More
Nonclassical States of Light and MechanicsNov 12 2012This book chapter reports on theoretical protocols for generating nonclassical states of light and mechanics. Nonclassical states are understood as squeezed states, entangled states or states with negative Wigner function, and the nonclassicality can ... More
Principal Component Analysis of Molecular Clouds: Can CO reveal the dynamics?Feb 10 2014We use Principal Component Analysis (PCA) to study the gas dynamics in numerical simulations of typical MCs. Our simulations account for the non-isothermal nature of the gas and include a simplified treatment of the time-dependent gas chemistry. We model ... More
Strong micro-macro entanglement from a weak cross-Kerr nonlinearityDec 09 2014We study the entanglement generated by a weak cross-Kerr nonlinearity between two initial coherent states, one of which has an amplitude close to the single-photon level, while the other one is macroscopic. We show that strong micro-macro entanglement ... More
Bridging microscopic nonlinear polarizations toward far-field second harmonic radiationNov 27 2017Since the first observation of second harmonic generation, there have been extensive studies on this nonlinear phenomenon, to not only clarify its physical origin but also realize unconventional applications, including multiplexed holography, bio-imaging, ... More
Small Drone Field Experiment: Data Collection & ProcessingNov 29 2017Following an initiative formalized in April 2016 formally known as ARL West between the U.S. Army Research Laboratory (ARL) and University of Southern California's Institute for Creative Technologies (USC ICT), a field experiment was coordinated and executed ... More
Giant and accessible conductivity of charged domain walls in lithium niobateMar 07 2017Ferroelectric domain walls are nm-sized interfaces between sections of different allowed values of the spontaneous polarization, the so-called domains. These walls - neutral or charged - can be created, displaced, deleted, and recreated again in ferroelectric ... More
Quantum repeaters based on Rydberg-blockade coupled atomic ensemblesMar 11 2010We propose a scheme for realizing quantum repeaters with Rydberg-blockade coupled atomic ensembles, based on a recently proposed collective encoding strategy. Rydberg-blockade mediated two-qubit gates and efficient cooperative photon emission are employed ... More
Two-photon dynamics in coherent Rydberg atomic ensembleJan 07 2014Mar 12 2014We study the interaction of two photons in a Rydberg atomic ensemble under the condition of electromagnetically induced transparency, combining a semi-classical approach for pulse propagation and a complete quantum treatment for quantum state evolution. ... More
Precision requirements for spin-echo based quantum memoriesDec 02 2010Spin echo techniques are essential for achieving long coherence times in solid-state quantum memories for light because of inhomogeneous broadening of the spin transitions. It has been suggested that unrealistic levels of precision for the radio frequency ... More
Practical private database queries based on a quantum key distribution protocolFeb 23 2010Sep 09 2010Private queries allow a user Alice to learn an element of a database held by a provider Bob without revealing which element she was interested in, while limiting her information about the other elements. We propose to implement private queries based on ... More
Adaptive resolution molecular dynamics simulation through coupling to an internal particle reservoirDec 14 2011Nov 11 2012For simulation studies of (macro) molecular liquids it would be of significant interest to be able to adjust or increase the level of resolution within one region of space, while allowing for the free exchange of molecules between open regions of different ... More
The Small-Scale Dynamo and Non-Ideal MHD in Primordial Star FormationApr 03 2012May 23 2012We study the amplification of magnetic fields during the formation of primordial halos. The turbulence generated by gravitational infall motions during the formation of the first stars and galaxies can amplify magnetic fields very efficiently and on short ... More
Decomposition of split-step quantum walks for simulating Majorana modes and edge statesMar 17 2017May 30 2017We construct a decomposition procedure for converting split-step quantum walks into ordinary quantum walks with alternating coins, and we show that this decomposition enables a feasible linear optical realization of split-step quantum walks by eliminating ... More
Quantum Synchronization Blockade: Energy Quantization hinders Synchronization of Identical OscillatorsMar 14 2017Jun 22 2017Classically, the tendency towards spontaneous synchronization is strongest if the natural frequencies of the self-oscillators are as close as possible. We show that this wisdom fails in the deep quantum regime, where the uncertainty of amplitude narrows ... More
Testing a Bell inequality in multi-pair scenariosOct 06 2008Nov 11 2008To date, most efforts to demonstrate quantum nonlocality have concentrated on systems of two (or very few) particles. It is however difficult in many experiments to address individual particles, making it hard to highlight the presence of nonlocality. ... More
Giant Optical Non-linearity induced by a Single Two-Level System interacting with a Cavity in the Purcell RegimeOct 20 2006Apr 23 2007A two-level system that is coupled to a high-finesse cavity in the Purcell regime exhibits a giant optical non-linearity due to the saturation of the two-level system at very low intensities, of the order of one photon per lifetime. We perform a detailed ... More
Performing private database queries in a real-world environment using a quantum protocolMar 04 2013Oct 16 2013In the well-studied cryptographic primitive 1-out-of-N oblivious transfer, a user retrieves a single element from a database of size N without the database learning which element was retrieved. While it has previously been shown that a secure implementation ... More
Relaxation dynamics of an isolated large-spin Fermi gas far from equilibriumDec 23 2013Mar 12 2014A fundamental question in many-body physics is how closed quantum systems reach equilibrium. We address this question experimentally and theoretically in an ultracold large-spin Fermi gas where we find a complex interplay between internal and motional ... More
Coherent multi-flavour spin dynamics in a fermionic quantum gasMar 05 2012Microscopic spin interaction processes are fundamental for global static and dynamical magnetic properties of many-body systems. Quantum gases as pure and well isolated systems offer intriguing possibilities to study basic magnetic processes including ... More
Probabilistic instantaneous quantum computationSep 04 2001Jan 08 2003The principle of teleportation can be used to perform a quantum computation even before its quantum input is defined. The basic idea is to perform the quantum computation at some earlier time with qubits which are part of an entangled state. At a later ... More
Etch-Tuning and Design of Silicon Nitride Photonic Crystal ReflectorsSep 03 2016Sep 08 2016By patterning a freestanding dielectric membrane into a photonic crystal reflector (PCR), it is possible to resonantly enhance its normal-incidence reflectivity, thereby realizing a thin, single-material mirror. In many PCR applications, the operating ... More
Testing Star Formation Laws in a Starburst Galaxy At Redshift 3 Resolved with ALMADec 11 2017Dec 18 2017Using high-resolution (sub-kiloparsec scale) submillimeter data obtained by ALMA, we analyze the star formation rate (SFR), gas content and kinematics in SDP 81, a gravitationally-lensed star-forming galaxy at redshift 3. We estimate the SFR surface density ... More