Latest in quant-ph

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Transmission spectra of an ultrastrongly coupled qubit-dissipative resonator systemJun 13 2019We calculate the transmission spectra of a flux qubit coupled to a dissipative resonator in the ultrastrong coupling regime. Such a qubit-oscillator system constitutes the building block of superconducting circuit QED platforms. The calculated transmission ... More
How the modified Bertrand theorem explains regularities of the periodic table I. From conformal invariance to Hopf mappingJun 13 2019Bertrand theorem permits closed orbits in 3d Euclidean space only for 2 types of central potentials. These are of Kepler-Coulomb and harmonic oscillator type. Volker Perlick recently extended Bertrand theorem. He designed new static spherically symmetric ... More
Stopped and stationary light at the single-photon level inside a hollow-core fiberJun 13 2019An experimental platform operating at the level of individual quanta is a key requirement for quantum information processing. We report on narrowband light storage and retrieval as well as stationary light for weak coherent light pulses down to the single-photon ... More
Adaptive Tracking of Enzymatic Reactions with Quantum LightJun 13 2019Enzymes are essential to maintain organisms alive. Some of the reactions they catalyze are associated with a change in reagents chirality, hence their activity can be tracked by using optical means. However, illumination affects enzyme activity: the challenge ... More
Evaluating the Holevo Cramér-Rao bound for multi-parameter quantum metrologyJun 13 2019Only with the simultaneous estimation of multiple parameters are the quantum aspects of metrology fully revealed. This is due to the incompatibility of observables. The fundamental bound for multi-parameter quantum estimation is the Holevo Cram\'er-Rao ... More
Cooperative spontaneous emission via renormalization approach: Classical versus semi-classical effectsJun 13 2019We address the many-atom emission of a dilute cloud of two-level atoms through a renormalized perturbation theory. An analytical solution for the truncated coupled-dipole equations is derived, which contains an effective spectrum associated to the initial ... More
Hilbert Space Fragmentation and Many-Body LocalizationJun 13 2019Investigating many-body localization (MBL) using exact numerical methods is limited by the exponential growth of the Hilbert space. However, localized eigenstates display multifractality and only extend over a vanishing fraction of the Hilbert space. ... More
Direct optical excitation of an NV center via a nanofiber Bragg-cavity: A theoretical simulationJun 13 2019Direct optical excitation of a nitrogen-vacancy (NV) center in nanodiamond by light via a nanofiber is of interest for all-fiber-integrated quantum applications. However, the background light induced by the excitation light via the nanofiber is problematic ... More
Invariant Off-Diagonality: SICs as Equicoherent Quantum StatesJun 13 2019Coherence, treated as a resource in quantum information theory, is a basis-dependent quantity. Looking for states that have constant coherence under canonical changes of basis yields highly symmetric structures in state space. For the case of a qubit, ... More
Control of quantum memory assisted entropic uncertainty lower bound for topological qubits in open quantum system through environmentJun 13 2019The uncertainty principle is one of the most important issues that clarify the distinction between classical and quantum theory. This principle sets a bound on our ability for prediction of the measurement outcomes of two incompatible observable precisely. ... More
Analysis of assumptions in BIG Bell Test experimentsJun 13 2019Recent group of experiments tested local realism with random choices prepared by humans. These various tests were subject to additional assumptions, which lead to loopholes in the interpretations of almost all the experiments. Among these assumptions ... More
Emergent Gauge Symmetries and Quantum OperationsJun 13 2019The algebraic approach to quantum physics emphasizes the role played by the structure of the algebra of observables and its relation to the space of states. An important feature of this point of view is that subsystems can be described by subalgebras, ... More
Simulating quantum thermodynamics of a finite system and bath with variable temperatureJun 13 2019We construct a finite bath with variable temperature for quantum thermodynamic simulations in which heat flows between a system $\mathcal{S}$ and the bath environment $\mathcal{E}$ in time evolution of an initial $\mathcal{SE}$ pure state. The bath consists ... More
Microwave Packaging for Superconducting QubitsJun 12 2019Over the past two decades, the performance of superconducting quantum circuits has tremendously improved. The progress of superconducting qubits enabled a new industry branch to emerge from global technology enterprises to quantum computing startups. ... More
Quantum security of the Fiat-Shamir transform of commit and open protocolsJun 12 2019Applying the Fiat-Shamir transform on identification schemes is one of the main ways of constructing signature schemes. While the classical security of this transformation is well understood, it is only very recently that generic results for the quantum ... More
Controllable Finite-Momenta Dynamical Quasicondensation in the Periodically Driven One-Dimensional Fermi-Hubbard ModelJun 12 2019In the strongly interacting limit of the Hubbard model localized double-occupancies form effective hard-core bosonic excitations, called a doublons, which are long-lived due to energy conservation. Using time-dependent density-matrix renormalisation group ... More
Evolution of Pair Correlation Symmetries and Supercurrent Reversal in Tilted Weyl SemimetalsJun 12 2019We study the effective symmetry profiles of superconducting pair correlations and the flow of charge supercurrent in ballistic Weyl semimetal systems with a tilted dispersion relation. Utilizing a microscopic method in the ballistic regime and starting ... More
Multifractality of open quantum systemsJun 12 2019We study the eigenstates of open maps whose classical dynamics is pseudointegrable and for which the corresponding closed quantum system has multifractal properties. Adapting the existing general framework developed for open chaotic quantum maps, we specify ... More
Strongly Correlated Quantum Gas Prepared by Direct Laser CoolingJun 12 2019We create a one-dimensional strongly correlated quantum gas of $^{133}$Cs atoms with attractive interactions by direct laser cooling in 300~ms. After compressing and cooling the optically trapped atoms to the vibrational ground state along two tightly ... More
Skymionic beamsJun 12 2019Vector vortex beams possess a topological property that derives both from the spatially varying amplitude of the field and also from its varying polarization. This property arises as a consequence of the natural Skyrmionic nature of such beams and is ... More
Twin-beam sub-shot-noise raster-scanning microscope with a hybrid detection schemeJun 12 2019By exploiting the quantised nature of light, we demonstrate a sub-shot-noise scanning optical transmittance microscope. Our microscope demonstrates, with micron scale resolution, a factor of improvement in precision of 1.76(9) in transmittance estimation ... More
Quantum Many-body Scars in a Landau Level on a Thin TorusJun 12 2019We study a kinetically constrained pair hopping model that arises within a Landau level in the quantum Hall effect. At filling $\nu = 1/3$, the model exactly maps onto the so-called ``PXP model", a constrained model for the Rydberg atom chain that is ... More
Out-of-time-order correlators at infinite temperature: Scrambling, Order and Topological Phase TransitionsJun 12 2019We report a numerical observation where the infinite-temperature out-of-time-order correlators (OTOCs) directly probe quantum phase transitions at zero temperature. This is in direct contrast to common intuition where quantum effects are washed away by ... More
Simulating quantum circuits by adiabatic computation: improved spectral gap estimates via eigenstate ansatzJun 12 2019Adiabatic quantum computing is a framework for quantum computing that is superficially very different to the standard circuit model. However, it can be shown that the two models are computationally equivalent. The key to the proof is a mapping of a quantum ... More
Electromagnetism at finite temperature: a density operator approachJun 12 2019In order to analyse classical electromagnetism in a medium at finite temperature, we introduce "optical density operator," and reformulate Maxwell equations with the operator, starting from the Dirac-equation-like formulation of electromagnetism. The ... More
Perfect control of photoelectron anisotropy for randomly oriented ensembles of molecules by XUV REMPI and polarization shapingJun 12 2019We report two schemes to generate perfect anisotropy in the photoelectron angular distribution of a randomly oriented ensemble of polyatomic molecules. In order to exert full control over the anisotropy of photoelectron emission, we exploit interferences ... More
Outcoupling from a Bose-Einstein condensate in the strong-field limitJun 12 2019Atoms can be extracted from a trapped Bose-Einstein condensate (BEC) by driving spin-flips to untrapped states. The coherence properties of the BEC are transfered to the released atoms, creating a coherent beam of matter refered to as an atom laser. In ... More
Parameter regimes for surpassing the PLOB bound with error-corrected qudit repeatersJun 12 2019A potential quantum internet would open up the possibility of realizing numerous new applications, including provably secure communication. Since losses of photons limit long-distance, direct quantum communication and widespread quantum networks, quantum ... More
Topological ordering in the Majorana Toric CodeJun 12 2019At zero temperature, a two-dimensional lattice of Majorana zero modes on mesoscopic superconducting islands exhibits a topologically-ordered toric code phase. Recently, a Landau field theory was used to describe the different phases of the aforementioned ... More
Observation of a large, resonant, cross-Kerr nonlinearity in a free-space Rydberg mediumJun 12 2019We report the experimental observation of a cross-Kerr nonlinearity in a free-space medium based on resonantly-excited, interacting Rydberg atoms and electromagnetically induced transparency. The nonlinearity is used to implement cross-phase modulation ... More
Entanglement as geometry and flowJun 12 2019We explore the connection between the area law for entanglement and geometry by representing the entanglement entropies corresponding to all $2^N$ bipartitions of an $N$-party pure quantum system by means of a (generalized) adjacency matrix. In the cases ... More
A generating integral for the matrix elements of the Coulomb Green's function with the Coulomb wave functionsJun 12 2019We analytically evaluate the generating integral $K_{nl}(\beta,\beta') = \int_{0}^{\infty}\int_{0}^{\infty} e^{-\beta r - \beta' r'}G_{nl} r^{q} r'^{q'} dr dr'$ and integral moments $J_{nl}(\beta, r') = \int_{0}^{\infty} dr' G_{nl}(r,r') r'^{q} e^{-\beta ... More
Heralded dissipative preparation of nonclassical states in a Kerr oscillatorJun 12 2019We present a heralded state preparation scheme for driven nonlinear open quantum systems. The protocol is based on a continuous photon counting measurement of the system's decay channel. When no photons are detected for a period of time, the system has ... More
A no-go result for the quantum damped harmonic oscillatorJun 12 2019In this letter we show that it is not possible to set up a canonical quantization for the damped harmonic oscillator using the Bateman lagrangian. In particular, we prove that no square integrable vacuum exists for the {\em natural} ladder operators of ... More
Generating single longitudinal mode entangled photons in telecom band via a submillimeter monolithic cavityJun 12 2019A high-quality, compact, and narrow-bandwidth entangled photon source (EPS) is indispensable for realization of many quantum communication protocols. Usually, a free space cavity containing a nonlinear crystal is used to generate a narrow bandwidth EPS ... More
Experimental observation of information flow in the anti-$\mathcal{PT}$-symmetric systemJun 12 2019The recently theoretical and experimental researches related to $\mathcal{PT}$-symmetric system have attracted unprecedented attention because of various novel features and potentials in extending canonical quantum mechanics. However, as the counterpart ... More
Elastic propagation of fast electron vortices through amorphous materialsJun 12 2019In this work, we study the elastic scattering behavior of electron vortices when propagating through amorphous samples. We use a formulation of the multislice approach in cylindrical coordinates to theoretically investigate the redistribution of intensity ... More
Enhanced spin state readout of Nitrogen-Vacancy centers in diamond using IR fluorescenceJun 12 2019Nitrogen-Vacancy (NV) centers in diamond have been used in recent years for a wide range of applications, from nano-scale NMR to quantum computation. These applications depend strongly on the efficient readout of the NV center's spin state, which is currently ... More
Continuous-variables quantum cryptography: asymptotic and finite-size security analysisJun 12 2019In this thesis we study the finite-size analysis of two continuous-variables quantum key distribution schemes. The first one is the one-way protocol using Gaussian modulation of thermal states and the other is the measurement-device-independent protocol. ... More
Many-body topological invariants from randomized measurementsJun 12 2019The classification of symmetry-protected topological (SPT) phases in one dimension has been recently achieved, and had a fundamental impact in our understanding of quantum phases in condensed matter physics. In this framework, SPT phases can be identified ... More
Partner formula for an arbitrary moving mirror in $1+1$ dimensionJun 12 2019In the information loss problem in black hole evaporation, investigation of the purification partner of a Hawking particle is crucial. It is a well-known fact that 3+1 dimensional spherically symmetric gravitational collapse can be approximately described ... More
Quantum Memory Assisted Precision Rotation SensingJun 12 2019We propose to implement a solid-state rotation sensor by employing a many-body quantum spin system which takes the advantages of the easy controllability of electron spin and the robustness provided by the collective nuclear spin state. The sensor consists ... More
Strong Chaos of Fast Scrambling Yields Order: Emergence of Decoupled Quantum Information CapsulesJun 12 2019The information loss problem in black hole evaporation is one of fundamental issues. Its resolution requires more profound understanding of information storage mechanism in quantum systems. In this Letter, we argue that when multiple unknown parameters ... More
One-shot Distillation in a General Resource TheoryJun 12 2019We present a general framework of a quantum resource theory based on the assumption of a) convexity and b) that the overlap of free states with maximally resourceful state is bounded. Using this structure, we derive bounds on the one-shot distillation ... More
Quantum mechanics as a noncommutative representation of classical conditional probabilitiesJun 12 2019The aim of this paper is to analyze the reconstructability of quantum mechanics from classical conditional probabilities representing measurement outcomes conditioned on measurement choices. We will investigate how the quantum mechanical representation ... More
Embedding entanglement generation within a measurement-feedback coherent Ising machineJun 12 2019We present a new scheme to efficiently establish entanglement between optical modes in a time-multiplexed coherent Ising machine (CIM) by means of nonlocal measurement and feedback. We numerically simulate and evaluate the generation of steady-state entanglement ... More
Testing macroscopic local realism using cat-states and Bell inequalities in timeJun 12 2019We show how one may test macroscopic local realism using nonlinear beam splitters, where $N$ bosons are either transmitted or reflected, after an interaction. Such beam-splitters are realisable (at least mesoscopically) with a nonlinear Josephson interaction, ... More
Testing macroscopic local realism using cat-states and Bell inequalities in timeJun 12 2019Jun 13 2019We show how one may test macroscopic local realism using nonlinear beam splitters, where $N$ bosons are either transmitted or reflected, after an interaction. Such beam-splitters are realisable (at least mesoscopically) with a nonlinear Josephson interaction, ... More
Quantum Kibble-Zurek physics in long-range transverse-field Ising modelsJun 12 2019We analyze the quantum phase transitions taking place in a one-dimensional transverse field Ising model with long-range couplings that decay algebraically with distance. We are interested in the Kibble-Zurek universal scaling laws emerging in non-equilibrium ... More
Fine's Theorem for Leggett-Garg tests with an arbitrary number of measurement timesJun 12 2019If the time evolution of a system can be understood classically, then there must exist an underlying probability distribution for the variables describing the system at all times. It is well known that for systems described by a single time-evolving dichotomic ... More
Resource-efficient and fault-tolerant topological quantum computation with hybrid entanglement of lightJun 11 2019We propose an all-linear-optical scheme to ballistically generate a cluster state for measurement based topological fault-tolerant quantum computation using hybrid photonic qubits entangled in a continuous-discrete domain. Availability of near-deterministic ... More
Evolution speed of open quantum dynamicsJun 11 2019The space of density matrices is embedded in a Euclidean space to deduce the dynamical equation satisfied by the state of an open quantum system. The Euclidean norm is used to obtain an explicit expression for the speed of the evolution of the state. ... More
Necessary conditions for steerability of two qubits, from consideration of local operationsJun 11 2019EPR-steering refers to the ability of one observer to convince a distant observer that they share entanglement by making local measurements. Determining which states allow a demonstration of EPR-steering remains an open problem in general, even for the ... More
Quantum, Nonlocal Aberration CancellationJun 11 2019Phase distortions, or aberrations, can negatively influence the performance of an optical imaging system. Through the use of position-momentum entangled photons, we nonlocally correct for aberrations in one photon's optical path by intentionally introducing ... More
Wavefunction positivization via automatic differentiationJun 11 2019We introduce a procedure to systematically search for a local unitary transformation that maps a wavefunction with a non-trivial sign structure into a positive-real form. The transformation is parametrized as a quantum circuit compiled into a set of one ... More
Nanoscale Sensing and Quantum CoherenceJun 11 2019Small solid state qubits, most prominently single spins in solids, can be remarkable sensors for various physical quantities ranging from magnetic fields to temperature. They package the performance of their bulk semiconductor counterparts into a nanoscale ... More
The low-energy Goldstone mode in a trapped dipolar supersolidJun 11 2019A supersolid is a counter-intuitive state of matter that combines the frictionless flow of a superfluid with the crystal-like periodic density modulation of a solid. Since the first prediction in the 1950s, experimental efforts to realize this state have ... More
Semiparametric estimation for incoherent optical imagingJun 11 2019The theory of semiparametric estimation offers an elegant way to compute the Cram\'er-Rao bound for a parameter of interest in the midst of infinitely many nuisance parameters. Here I apply the theory to the problem of moment estimation for incoherent ... More
On the explicit constructions of certain unitary $t$-designsJun 11 2019Unitary $t$-designs are `good' finite subsets of the unitary group $U(d)$ that approximate the whole unitary group $U(d)$ well. Unitary $t$-designs have been applied in randomized benchmarking, tomography, quantum cryptography and many other areas of ... More
The possibility of direct observation of the Bloch-Siegert shift in coherent dynamics of multiphoton Raman transitionsJun 11 2019We study Rabi oscillations of the second-order Raman transition realized on dressed states of a qubit excited by an amplitude-modulated microwave field. The co-rotating component of the ultrastrong low-frequency modulation field excites virtual multiple ... More
The Non-m-Positive Dimension of a Positive Linear MapJun 11 2019We introduce a property of a matrix-valued linear map $\Phi$ that we call its "non-m-positive dimension" (or "non-mP dimension" for short), which measures how large a subspace can be if every quantum state supported on the subspace is non-positive under ... More
Testing the gravitational field generated by a quantum superpositionJun 11 2019What gravitational field is generated by a massive quantum system in a spatial superposition? Despite decades of intensive theoretical and experimental research, we still do not know the answer. On the experimental side, the difficulty lies in the fact ... More
Coherent transfer of quantum information in silicon using resonant SWAP gatesJun 11 2019Solid state quantum processors based on spins in silicon quantum dots are emerging as a powerful platform for quantum information processing. High fidelity single- and two-qubit gates have recently been demonstrated and large extendable qubit arrays are ... More
Generalized Product Formulas and Quantum ControlJun 11 2019We study the quantum evolution under the combined action of the exponentials of two not necessarily commuting operators. We consider the limit in which the two evolutions alternate at infinite frequency. This case appears in a plethora of situations, ... More
A quantum walk with both a continuous-time and a continuous-spacetime limitJun 11 2019Nowadays, quantum simulation schemes come in two flavours. Either they are continuous-time discrete-space models (a.k.a Hamiltonian-based), pertaining to non-relativistic quantum mechanics. Or they are discrete-spacetime models (a.k.a Quantum Walks or ... More
A short introduction to the Lindblad Master EquationJun 11 2019The theory of open quantum system is one of the most important tools for the development of quantum technologies. Furthermore, the Lindblad (or Gorini- Kossakowski-Sudarshan-Lindblad) Master Equation plays a key role as it is the most general generator ... More
Floquet oscillations in periodically driven Dirac systemsJun 11 2019Electrons in a lattice exhibit time-periodic motion, known as Bloch oscillation, when subject to an additional static electric field. Here we show that a corresponding dynamics can occur upon replacing the spatially periodic potential by a time-periodic ... More
A quantum emitter coated with graphene interacting in the strong coupling regimeJun 11 2019Jun 12 2019We investigate the optical response of a graphene spherical shell which has a semi-conducting material core through their absorption spectrum. The semi-conducting material is described by a Lorenztian expression, which approximates the optical responce ... More
A quantum emitter coated with graphene interacting in the strong coupling regimeJun 11 2019We investigate the optical response of a graphene spherical shell which has a semi-conducting material core through their absorption spectrum. The semi-conducting material is described by a Lorenztian expression, which approximates the optical responce ... More
Fast-forward approach to adiabatic quantum dynamics of regular spin clusters: nature of geometry-dependent driving interactionsJun 11 2019The fast forward scheme of adiabatic quantum dynamics is applied to finite regular spin clusters with various geometries and the nature of driving interactions is elucidated. The fast forward is the quasi-adiabatic dynamics guaranteed by regularization ... More
Quantum satellites and tests of relativityJun 11 2019Deployment of quantum technology in space provides opportunities for new types of precision tests of gravity. On the other hand, the operational demands of such technology can make previously unimportant effects practically relevant. We describe a novel ... More
Quantum Random Numbers generated by the Cloud Superconducting Quantum ComputerJun 11 2019A cloud quantum computer is similar to a random number generator in that its physical mechanism is inaccessible to the users. In this respect, a cloud quantum computer is a black box. In both devices, the users decide the device condition from the output. ... More
A cosmic shadow on CSLJun 11 2019The Continuous Spontaneous Localisation (CSL) model solves the measurement problem of standard quantum mechanics, by coupling the mass density of a quantum system to a white-noise field. Since the mass density is not uniquely defined in general relativity, ... More
Discovery of ST1 centers in natural diamondJun 11 2019The ST1 center is a point defect in diamond with bright fluorescence and a mechanism for optical spin initialization and readout. The center has impressive potential for applications in diamond quantum computing as a quantum bus to a register of nuclear ... More
Multi-level quantum Rabi model for anharmonic vibrational polaritonsJun 11 2019We propose a cavity QED approach to describe light-matter interaction between an individual anharmonic molecular vibration and an infrared cavity field. Starting from a generic Morse oscillator with quantized nuclear motion, we derive a multi-level quantum ... More
An optimized twist angle to find the twist-averaged correlation energy applied to the uniform electron gasJun 11 2019We explore an alternative to twist averaging in order to obtain more cost-effective and accurate extrapolations to the thermodynamic limit (TDL) for coupled cluster doubles (CCD) calculations. We seek a single twist angle to perform calculations at, instead ... More
General Linear Group Action on Tensors: A Candidate for Post-Quantum CryptographyJun 11 2019Starting from the one-way group action framework of Brassard and Yung (Crypto '90), we revisit building cryptography based on group actions. Several previous candidates for one-way group actions no longer stand, due to progress both on classical algorithms ... More
Bell's Theorem and Spacetime-Based Reformulations of Quantum MechanicsJun 10 2019In this critical review of Bell's Theorem, its implications for reformulations of quantum theory are considered. The assumptions of the theorem are set out explicitly, within a framework of mathematical models with well-defined inputs and outputs. Attention ... More
Thermodynamic bounds on coherent transport in periodically driven conductorsJun 10 2019We establish a family of new thermodynamic constraints on heat and particle transport in coherent multi-terminal conductors subject to slowly oscillating driving fields as well as moderate electrical and thermal biases. These bounds depend only on the ... More
The structure of chaotic eigenstates and their entanglement entropyJun 10 2019We consider a chaotic many-body system that is split into two subsystems, with an interaction along their mutual boundary, and study the entanglement properties of an energy eigenstate with nonzero energy density. When the two subsystems have nearly equal ... More
Polaron-transformed dissipative Lipkin-Meshkov-Glick ModelJun 10 2019We investigate the Lipkin-Meshkov-Glick model coupled to a thermal bath. Since the isolated model itself exhibits a quantum phase transition, we explore the critical signatures of the open system. Starting from a system-reservoir interaction written in ... More
How much entanglement can be created in a closed system?Jun 10 2019In a closed system, the total number of particles is fixed. We ask how much does this conservation law restricts the amount of entanglement that can be created. We derive a tight upper bound on the bipartite entanglement entropy in closed systems, and ... More
Magic entanglement renormalization for quantum fieldsJun 10 2019Continuous tensor networks are variational wavefunctions proposed in recent years to efficiently simulate quantum field theories (QFTs). Prominent examples include the continuous matrix product state (cMPS) and the continuous multi-scale entanglement ... More
Twisted and untwisted negativity spectrum of free fermionsJun 10 2019A basic diagnostic of entanglement in mixed quantum states is known as the positive partial transpose (PT) criterion. Such criterion is based on the observation that the spectrum of the partially transposed density matrix of an entangled state contains ... More
Adaptive optics benefit for quantum key distribution uplink from ground to a satelliteJun 10 2019For quantum communications, the use of Earth-orbiting satellites to extend distances has gained significant attention in recent years, exemplified in particular by the launch of the Micius satellite in 2016. The performance of applied protocols such as ... More
Disentangling the Generalized Double Semion ModelJun 10 2019We analyze the class of Generalized Double Semion (GDS) models in arbitrary dimensions from the point of view of lattice Hamiltonians. We show that on a $d$-dimensional spatial manifold $M$ the dual of the GDS is equivalent, up to constant depth local ... More
Complexity phase diagram for interacting and long-range bosonic HamiltoniansJun 10 2019Recent years have witnessed a growing interest in topics at the intersection of many-body physics and complexity theory. Many-body physics aims to understand and classify emergent behavior of systems with a large number of particles, while complexity ... More
Experimental kernel-based quantum machine learning in finite feature spaceJun 10 2019We implement an all-optical setup demonstrating kernel-based quantum machine learning for two-dimensional classification problems. In this hybrid approach, kernel evaluations are outsourced to projective measurements on suitably designed quantum states ... More
Bayesian multi-parameter quantum metrology with limited dataJun 10 2019We propose a strategy to study - and possibly design - protocols for multi-parameter scenarios where the measurement data is limited, and for which our prior knowledge is moderate. While this is a realistic regime that emerges frequently in practice, ... More
High-dimension experimental tomography of a path-encoded photon quantum-stateJun 10 2019Quantum information protocols often rely on tomographic techniques to determine the state of the system. A popular method of encoding information is on the different paths a photon may take, for example, parallel waveguides in integrated optics. However, ... More
Loop update for infinite projected entangled-pair states in two spatial dimensionsJun 10 2019We propose an improved approach to carry out the imaginary time evolution of infinite projected entangled-pair states (iPEPS), especially for systems with criticality. A cyclic optimal truncation is introduced to update the tensors along a closed loop, ... More
Coherence cost for violating conservation lawsJun 10 2019The laws of physics place many restrictions on the operations that we can perform. Many of these restrictions require some ``resource'' as a cost to realize the desired operation. For example, the Wigner-Araki-Yanase theorem, a remarkable theorem on quantum ... More
Mass-energy equivalence in harmonically trapped particlesJun 10 2019Precise understanding of the dynamics of trapped particles is crucial for nascent quantum technologies, including atomic clocks and quantum simulators. Here we present a framework to systematically include quantum effects arising from the mass-energy ... More
Dissipative quantum state preparation and metastability in two-photon micromasersJun 10 2019We study the preparation of coherent quantum states via a two-photon micromaser for applications in quantum metrology. While this setting can be in principle realized in a host of physical systems, we focus here on a situations where atoms interact with ... More
Nonlinear evolution and signalingJun 10 2019We propose a condition, called convex quasi-linearity, for deterministic nonlinear quantum evolutions. Evolutions satisfying this condition do not allow for arbitrary fast signaling, therefore, they cannot be ruled out by a standard argument. We also ... More
Quantum supremacy with analog quantum processors for material science and machine learningJun 10 2019Quantum supremacy is the ability of quantum processors to outperform classical computers at certain tasks. In digital random quantum circuit approaches for supremacy, the output distribution produced is described by the Porter-Thomas (PT) distribution. ... More
Quantum algorithm for logistic regressionJun 10 2019Logistic regression (LR) is an important machine learning model for classification, with wide applications in text classification, image analysis, medicine diagnosis, etc. However, training LR generally entails an iterative the gradient descent method, ... More
Machine learning continuous-variable quantum key distribution embedded with quantum multi-label classifierJun 10 2019We propose a brand-new protocol called machine learning continuous-variable quantum key distribution (ML-CVQKD), aiming to break the limitation of traditional pattern in CVQKD and establish a cross research platform between CVQKD and machine learning. ... More
Sequential nonabsorbing microwave single-photon detectorJun 10 2019We propose a nonabsorbing microwave single-photon detector that uses an artificial atom as a coherent interaction mediator between a traveling photon and a high-Q resonator, fully exploiting the knowledge of the photon's arrival time. Our proposal can ... More
Room Temperature Initialisation and Readout of Intrinsic Spin Defects in a Van der Waals CrystalJun 10 2019Optically addressable spins in widebandgap semiconductors have become one of the most prominent platforms for exploring fundamental quantum phenomena. While several candidates in 3D crystals including diamond and silicon carbide have been extensively ... More