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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.

Can quantum physics help solve the hard problem of consciousness? A hypothesis based on entangled spins and photonsSep 08 2018The hard problem of consciousness is the question how subjective experience arises from brain matter. I suggest exploring the possibility that quantum physics could be part of the answer. The simultaneous unity and complexity of subjective experience ... More

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

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

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

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

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

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

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

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

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

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

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

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.

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

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

Quantum Repeaters based on Single Trapped IonsFeb 18 2009Mar 25 2009We analyze the performance of a quantum repeater protocol based on single trapped ions. At each node, single trapped ions embedded into high finesse cavities emit single photons whose polarization is entangled with the ion state. A specific detection ... More

Temperatures are not useful to characterise bright-soliton experiments for ultra-cold atomsOct 28 2016Contrary to many other translationally invariant one-dimensional models, the low-temperature phase for an attractively interacting one-dimensional Bose-gas (a quantum bright soliton) is stable against thermal fluctuations. However, treating the thermal ... 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

Photon-photon gates in Bose-Einstein condensatesSep 30 2010It has recently been shown that light can be stored in Bose-Einstein condensates for over a second. Here we propose a method for realizing a controlled phase gate between two stored photons. The photons are both stored in the ground state of the effective ... 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

Towards long-distance quantum networks with superconducting processors and optical linksDec 20 2018We design a quantum repeater architecture, necessary for long distance quantum networks, using the recently proposed microwave cat state qubits, formed and manipulated via interaction between a superconducting nonlinear element and a microwave cavity. ... 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

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

Theory of cavity-enhanced non-destructive detection of photonic qubits in a solid-state atomic ensembleJul 12 2018Non-destructive detection of photonic qubits will enable important applications in photonic quantum information processing and quantum communications. Here, we present an approach based on a solid-state cavity containing an ensemble of rare-earth ions. ... 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

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

Proposal for the Creation and Optical Detection of Spin Cat States in Bose-Einstein CondensatesApr 04 2014Aug 20 2014We propose a method to create "spin cat states", i.e. macroscopic superpositions of coherent spin states, in Bose-Einstein condensates using the Kerr nonlinearity due to atomic collisions. Based on a detailed study of atom loss, we conclude that cat sizes ... 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

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

Coherent Logic Gate for Light Pulses based on Storage in a Bose-Einstein CondensateNov 30 2012A classical logic gate connecting input and output light pulses is demonstrated. The gate operation is based on three steps: First, two incoming light pulses are stored in a Bose-Einstein condensate, second, atomic four-wave mixing generates a new matter ... 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

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

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

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

Feasibility of efficient room-temperature solid-state sources of indistinguishable single photons using ultrasmall mode volume cavitiesOct 10 2017May 16 2018Highly efficient sources of indistinguishable single photons that can operate at room temperature would be very beneficial for many applications in quantum technology. We show that the implementation of such sources is a realistic goal using solid-state ... 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

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

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

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

Large Energy Superpositions via Rydberg DressingSep 03 2015Jun 20 2016We propose to create superposition states of over 100 Strontium atoms being in a ground state or metastable optical clock state, using the Kerr-type interaction due to Rydberg state dressing in an optical lattice. The two components of the superposition ... 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

AirLab: Autograd Image Registration LaboratoryJun 26 2018Medical image registration is an active research topic and forms a basis for many medical image analysis tasks. Although image registration is a rather general concept specialized methods are usually required to target a specific registration problem. ... More

Towards a Room-Temperature Spin-Photon Interface based on Nitrogen-Vacancy centers and OptomechanicsNov 06 2017Feb 03 2019The 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

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

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

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

Phase-matching condition for enhanced entanglement of colliding indistinguishable quantum bright solitons in a harmonic trapOct 03 2013Dec 10 2013We investigate finite number effects in collisions between two states of an initially well defined number of identical bosons with attractive contact interactions, oscillating in the presence of harmonic confinement in one dimension. We investigate two ... More

From short-time diffusive to long-time ballistic dynamics: the unusual center-of-mass motion of quantum bright solitonsJul 29 2014May 22 2015Brownian motion is ballistic on short time scales and diffusive on long time scales. Our theoretical investigations indicate that one can observe the exact opposite - an "anomaleous diffusion process" where initially diffusive motion becomes ballistic ... 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

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

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

Photonic quantum memory using intra-atomic frequency combOct 17 2018Photonic quantum memory, such as atomic frequency comb (AFC), is essential to make photonic quantum computation and long distance quantum communication scalable and feasible. In standard AFC the frequency of different atoms must be stable relative to ... More

Swept-Frequency Drumhead Mechanical ResonatorsAug 30 2018We demonstrate a high-Q ($>5 \times 10^{6}$) swept-frequency membrane mechanical resonator achieving octave resonance tuning via an integrated heater and an unprecedented acceleration noise floor below 1 $\mu$g Hz$^{-1/2}$ for frequencies above 50 kHz. ... 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

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

Superballistic center-of-mass motion in one-dimensional attractive Bose gases: Decoherence-induced Gaussian random walks in velocity spaceOct 18 2015Jan 09 2017We show that the spreading of the center-of-mass density 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 ... 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

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

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

Vectorial near-field couplingJan 31 2018The coherent exchange of optical near fields between two neighboring dipoles plays an essential role for the optical properties, quantum dynamics and thus for the function of many naturally occurring and artificial nanosystems. These interactions are ... 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

Terahertz light-matter interaction beyond unity coupling strengthJul 02 2018Achieving control over light-matter interaction in custom-tailored nanostructures is at the core of modern quantum electrodynamics [1-15]. In ultrastrongly coupled systems [5-15], excitation is repeatedly exchanged between a resonator and an electronic ... 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

Learning Unsupervised Multi-View Stereopsis via Robust Photometric ConsistencyMay 07 2019We present a learning based approach for multi-view stereopsis (MVS). While current deep MVS methods achieve impressive results, they crucially rely on ground-truth 3D training data, and acquisition of such precise 3D geometry for supervision is a major ... More

Controllable-dipole quantum memoryJun 17 2011Jun 07 2012We present a quantum memory protocol for photons that is based on the direct control of the transition dipole moment. We focus on the case where the light-matter interaction is enhanced by a cavity. We show that the optimal write process (maximizing the ... More

Bose-Einstein condensate as a quantum memory for a photonic polarization qubitDec 20 2011Feb 14 2012A scheme based on electromagnetically induced transparency is used to store light in a Bose-Einstein condensate. In this process, a photonic polarization qubit is stored in atomic Zeeman states. The performance of the storage process is characterized ... More

Raman quantum memory based on an ensemble of nitrogen-vacancy centers coupled to a microcavityDec 18 2013We propose a scheme to realize optical quantum memories in an ensemble of nitrogen-vacancy centers in diamond that are coupled to a micro-cavity. The scheme is based on off-resonant Raman coupling, which allows one to circumvent optical inhomogeneous ... More

Cross-phase modulation of a probe stored in a waveguide for non-destructive detection of photonic qubitsOct 05 2015Non-destructive detection of photonic qubits is an enabling technology for quantum information processing and quantum communication. For practical applications such as quantum repeaters and networks, it is desirable to implement such detection in a way ... More

Prospective applications of optical quantum memoriesJun 28 2013An optical quantum memory can be broadly defined as a system capable of storing a useful quantum state through interaction with light at optical frequencies. During the last decade, intense research was devoted to their development, mostly with the aim ... More

Creating Single Collective Atomic Excitations via Spontaneous Raman Emission in Inhomogeneously Broadened Systems : Beyond the Adiabatic ApproximationMar 18 2009The creation of single collective excitations in atomic ensembles via spontaneous Raman emission plays a key role in several quantum communication protocols, starting with the seminal DLCZ protocol [L.-M.Duan, M.D. Lukin, J.I. Cirac, and P. Zoller, Nature ... More

Phase noise measurements in long fiber interferometers for quantum repeaters applicationsDec 05 2007Aug 18 2008Many protocols for long distance quantum communication require interferometric phase stability over long distances of optical fibers. In this paper we investigate the phase noise in long optical fibers both in laboratory environment and in installed commercial ... More

Rate-loss analysis of an efficient quantum repeater architectureApr 28 2014Sep 14 2015We analyze an entanglement-based quantum key distribution (QKD) architecture that uses a linear chain of quantum repeaters employing photon-pair sources, spectral-multiplexing, linear-optic Bell-state measurements, multi-mode quantum memories and classical-only ... More

Far-field linear optical superresolution via heterodyne detection in a higher-order local oscillator modeJun 08 2016Jun 09 2016The Rayleigh limit has so far applied to all microscopy techniques that rely on linear optical interaction and detection in the far field. Here we demonstrate that detecting the light emitted by an object in higher-order transverse electromagnetic modes ... 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

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

Efficiency of an enhanced linear optical Bell-state measurement scheme with realistic imperfectionsAug 31 2015Sep 22 2016We compare the standard 50%-efficient single beam splitter method for Bell-state measurement to a proposed 75%-efficient auxiliary-photon-enhanced scheme [W. P. Grice, Phys. Rev. A 84, 042331 (2011)] in light of realistic conditions. The two schemes are ... 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

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

Practical Quantum Repeaters with Parametric Down-Conversion SourcesMay 13 2015Conventional wisdom suggests that realistic quantum repeaters will require quasi-deterministic sources of entangled photon pairs. In contrast, we here study a quantum repeater architecture that uses simple parametric down-conversion sources, as well as ... More

Efficient Differentiable Programming in a Functional Array-Processing LanguageJun 06 2018We present a system for the automatic differentiation of a higher-order functional array-processing language. The core functional language underlying this system simultaneously supports both source-to-source automatic differentiation and global optimizations ... More

Creating cat states in one-dimensional quantum walks using delocalized initial statesMay 24 2016Sep 15 2016Cat states are coherent quantum superpositions of macroscopically distinct states and are useful for understanding the boundary between the classical and the quantum world. Due to their macroscopic nature, cat states are difficult to prepare in physical ... More

Creation of equal-spin triplet superconductivity at the Al/EuS interfaceNov 21 2018In conventional superconductors, electrons of opposite spins are bound into Cooper pairs. However, when the superconductor is in contact with a non-uniformly ordered ferromagnet, an exotic type of superconductivity can appear at the interface, with electrons ... More

Three-photon energy-time entanglementMar 28 2012Entangled quantum particles have correlations stronger than those allowed by classical physics. These correlations are the focus of of the deepest issues in quantum mechanics [1-3] and are the basis of many quantum technologies. The entanglement of discrete ... More

Transverse multi-mode effects on the performance of photon-photon gatesJun 18 2010Feb 18 2011The multi-mode character of quantum fields imposes constraints on the implementation of high-fidelity quantum gates between individual photons. So far this has only been studied for the longitudinal degree of freedom. Here we show that effects due to ... More