Multi-photon entanglement and interferometry

Abstract

Multi-photon interference reveals strictly non-classical phenomena. Its applications range from fundamental tests of quantum mechanics to photonic quantum information processing, where a significant fraction of key experiments achieved so far comes from multi-photon state manipulation. We review the progress, both theoretical and experimental, of this rapidly advancing research. The emphasis is given to the creation of photonic entanglement of various forms, tests of the completeness of quantum mechanics (in particular, violations of local realism), quantum information protocols for quantum communication (e.g., quantum teleportation, entanglement purification and quantum repeater), and quantum computation with linear optics. We shall limit the scope of our review to "few photon" phenomena involving measurements of discrete observables.

71 pages, 38 figures; updated version accepted by Rev. Mod. Phys

References in corpus (108)

• Quantum entanglement
• The Quantum Internet
• Experimental quantum teleportation
• Entanglement detection
• Photonic quantum technologies
• Quantum interface between light and atomic ensembles
• Free-Space distribution of entanglement and single photons over 144 km
• Optical Quantum Computing
• Measurement-based quantum computation
• Hidden Variables and the Two Theorems of John Bell
• Silica-on-Silicon Waveguide Quantum Circuits
• Quantum walks of correlated particles
• Review: Semiconductor Quantum Light Sources
• Entangled Photon Pairs from Semiconductor Quantum Dots
• Beating the channel capacity limit for linear photonic superdense coding
• Experimental demonstration of quantum memory for light
• Beating the Standard Quantum Limit with Four Entangled Photons
• Resource-efficient linear optical quantum computation
• Towards Quantum Chemistry on a Quantum Computer
• Quantum key distribution over 40 dB channel loss using superconducting single photon detectors
• Experimental entanglement of six photons in graph states
• Heralded Generation of Ultrafast Single Photons in Pure Quantum States
• Topological fault-tolerance in cluster state quantum computation
• Stationary pulses of light in an atomic medium
• A simple test for hidden variables in spin-1 system
• Mapping photonic entanglement into and out of a quantum memory
• Research on Hidden Variable Theories: a review of recent progresses
• Experimental demonstration of a BDCZ quantum repeater node
• Shor's quantum factoring algorithm on a photonic chip
• A wavelength-tunable fiber-coupled source of narrowband entangled photons
• Experimental demonstration of a heralded entanglement source
• Observation of eight-photon entanglement
• An experimental test of non-local realism
• Bell inequality violation with two remote atomic qubits
• Experimental Long-Distance Decoy-State Quantum Key Distribution Based On Polarization Encoding
• Functional Quantum Nodes for Entanglement Distribution over Scalable Quantum Networks
• High-speed linear optics quantum computing using active feed-forward
• Detecting Genuine Multipartite Entanglement with Two Local Measurements
• Long distance decoy state quantum key distribution in optical fiber
• Experimental demonstration of a hyper-entangled ten-qubit Schrödinger cat state
• Tunable Indistinguishable Photons From Remote Quantum Dots
• Experimental demonstration of Shor's algorithm with quantum entanglement
• Entangling Independent Photons by Time Measurement
• Experimental realization of Dicke states of up to six qubits for multiparty quantum networking
• Experimental non-classicality of an indivisible quantum system
• Quantum Beat of Two Single Photons
• Experimental entanglement of a six-photon symmetric Dicke state
• A millisecond quantum memory for scalable quantum networks
• Experimental Analysis of a 4-Qubit Cluster State
• Demonstration of Shor's quantum factoring algorithm using photonic qubits
• Experimental Observation of Four-Photon Entangled Dicke State with High Fidelity
• Closing the detection loophole in Bell experiments using qudits
• Polarization entangled state measurement on a chip
• How good must single photon sources and detectors be for efficient linear optical quantum computation?
• An avalanche-photodiode-based photon-number-resolving detector
• Robust creation of entanglement between ions in spatially separate cavities
• State-independent quantum contextuality with single photons
• Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber
• Experimental Quantum Teleportation of a Two-Qubit Composite System
• Optimal control of light pulse storage and retrieval
• High-fidelity transmission of entanglement over a high-loss freespace channel
• Experimental interference of independent photons
• Experimental realization of one-way quantum computing with two-photon four-qubit cluster states
• Photonic crystal fibre source of photon pairs for quantum information processing
• Generation of Narrow-Band Polarization-Entangled Photon Pairs for Atomic Quantum Memories
• Quantum simulation of the wavefunction to probe frustrated Heisenberg spin systems
• Heralded generation of entangled photon pairs
• Generation and transfer of single photons on a photonic crystal chip
• Toolbox for entanglement detection and fidelity estimation
• Quantum entanglement of a large number of photons
• A fast and robust approach to long-distance quantum communication with atomic ensembles
• Deterministic single photons via conditional quantum evolution
• Demonstrating anyonic fractional statistics with a six-qubit quantum simulator
• Multistage Entanglement Swapping
• Experimental observation of an entire family of four-photon entangled states
• Experimental Falsification of Leggett's Non-Local Variable Model
• Conditional control of the quantum states of remote atomic memories for quantum networking
• Nonclassical 2-photon interference with separate intrinsically narrowband fibre sources
• Generation of high-fidelity four-photon cluster state and quantum-domain demonstration of one-way quantum computing
• Experimental test of nonlocal realistic theories without the rotational symmetry assumption
• High-fidelity entanglement swapping with fully independent sources
• A scheme for demonstration of fractional statistics of anyons in an exactly solvable model
• Efficient retrieval of a single excitation stored in an atomic ensemble
• High-fidelity operation of quantum photonic circuits
• Realization of a Knill-Laflamme-Milburn C-NOT gate -a photonic quantum circuit combining effective optical nonlinearities
• A pulsed Sagnac source of narrowband polarization-entangled photons
• Experimental Realization of a Controlled-NOT Gate with Four-Photon Six-Qubit Cluster States
• Proposed Bell experiment with genuine energy-time entanglement
• Scalable Generation of Graph-State Entanglement through Realistic Linear Optics
• Optical Nondestructive Controlled-NOT Gate without Using Entangled Photons
• Experimental quantum coding against photon loss error
• Optical Quantum Computation
• Synchronized Independent Narrow-band Single Photons and Efficient Generation of Photonic Entanglement
• High performance NbN nanowire superconducting single photon detectors fabricated on MgO substrates
• The Wavefunction of an Anyon
• Towards a loophole-free test of Bell's inequality with entangled pairs of neutral atoms
• Experimental Demonstration of Decoherence-Free One-Way Information Transfer
• Multi-qubit entanglement engineering via projective measurements
• Efficient construction of 2-D cluster states with probabilistic quantum gates
• One-way quantum computation with two-photon multiqubit cluster states
• Delay of Squeezing and Entanglement using Electromagnetically Induced Transparency in a Vapour Cell
• Preparation of Decoherence Free Cluster States with Optical Superlattices
• Interference contrast in multi-source few photon optics
• Experimentally generating and tuning robust entanglement between photonic qubits
• One-way quantum computing in a decoherence-free subspace
• Error tolerance and tradeoffs in loss- and failure-tolerant quantum computing schemes
• Quantum repeaters based on atomic ensembles and linear optics
• Linear optical quantum computation with imperfect entangled photon-pair sources and inefficient non-photon-number-resolving detectors

Cited by in corpus (615)

• Bell nonlocality
• Entanglement detection
• Secure quantum key distribution with realistic devices
• Near optimal single photon sources in the solid state
• Measuring entanglement entropy through the interference of quantum many-body twins
• Universal Linear Optics
• Cavity-based quantum networks with single atoms and optical photons
• Ground-to-satellite quantum teleportation
• On-Demand Single Photons with High Extraction Efficiency and Near-Unity Indistinguishability from a Resonantly Driven Quantum Dot in a Micropillar
• Twisted Photons: New Quantum Perspectives in High Dimensions
• Broadband waveguide quantum memory for entangled photons
• On-demand semiconductor single-photon source with near-unity indistinguishability
• Experimental ten-photon entanglement
• On-chip quantum interference between silicon photon-pair sources
• Quantum limits in optical interferometry
• Boson sampling with 20 input photons in 60-mode interferometers at $10^{14}$ state spaces
• On-demand generation of indistinguishable polarization-entangled photon pairs
• Towards optimal single-photon sources from polarized microcavities
• 18-qubit entanglement with photon's three degrees of freedom
• Metasurfaces for Quantum Photonics
• Experimental demonstration of a heralded entanglement source
• Fisher Information and entanglement of non-Gaussian spin states
• 12-photon entanglement and scalable scattershot boson sampling with optimal entangled-photon pairs from parametric down-conversion
• Entanglement Distillation between Solid-State Quantum Network Nodes
• Nonlinear optical signals and spectroscopy with quantum light
• On-demand semiconductor source of entangled photons which simultaneously has high fidelity, efficiency, and indistinguishability
• Active learning machine learns to create new quantum experiments
• Witnessing Quantum Coherence: from solid-state to biological systems
• Micius quantum experiments in space
• Deterministic quantum teleportation of photonic quantum bits by a hybrid technique
• Perspective: Toward large-scale fault-tolerant universal photonic quantum computing
• Delayed-choice gedanken experiments and their realizations
• Macroscopic quantum states: measures, fragility and implementations
• Quantum-Enhanced Sensing Based on Time Reversal of Nonlinear Dynamics
• Towards real-world quantum networks: a review
• Entanglement-Based Machine Learning on a Quantum Computer
• Bell nonlocality in networks
• BosonSampling with single-photon Fock states from a bright solid-state source
• Long-Distance Measurement-Device-Independent Multiparty Quantum Communication
• Observation of Laughlin states made of light
• Near Transform-Limited Single Photons from an Efficient Solid-State Quantum Emitter
• Quantum Image Processing and Its Application to Edge Detection: Theory and Experiment
• Frequency-domain Hong-Ou-Mandel interference
• Three-photon bosonic coalescence in an integrated tritter
• Phonon limit to simultaneous near-unity efficiency and indistinguishability in semiconductor single photon sources
• Direct generation of three-photon polarization entanglement
• Experimental Quantum Computing to Solve Systems of Linear Equations
• Photonic tensor networks produced by a single quantum emitter
• Quantum dots for photonic quantum information technology
• Entangled Mechanical Oscillators
• Experimental GHZ Entanglement beyond Qubits
• Nonseparable states of light: From quantum to classical
• Semiconductor devices for entangled photon pair generation: a review
• Experimental Machine Learning of Quantum States
• Quantum Conference Key Agreement: A Review
• A Time-Multiplexed Heralded Single-Photon Source
• Quantifying photonic high-dimensional entanglement
• Entanglement by Path Identity
• Observation of three-photon bound states in a quantum nonlinear medium
• Entangled Photon-Pair Sources based on three-wave mixing in bulk crystals
• Secret Sharing with a Single d-level Quantum System
• Enhancement in performance of quantum battery by ordered and disordered interactions
• Optomechanical sensing of spontaneous wave-function collapse
• Experimental Three-Particle Quantum Nonlocality under Strict Locality Conditions
• Fast charging of quantum battery assisted by noise
• Cascaded emission of single photons from the biexciton in monolayered WSe2
• Noisy intermediate-scale quantum computers
• Subnatural-linewidth biphotons from a Doppler-broadened hot atomic vapor cell
• Quantum Cloning Machines and the Applications
• Hybrid Entangled Entanglement in Vector Vortex Beams
• Bipartite and tripartite output entanglement in 3-mode optomechanical systems
• Entanglement in indistinguishable particle systems
• Macroscopic quantum entanglement in modulated optomechanics
• Solid-state ensemble of highly entangled photon sources at rubidium atomic transitions
• Partial indistinguishability theory for multi-photon experiments in multiport devices
• Optical parametric generation in a lithium niobate microring with modal phase matching
• Quantum-memory-assisted multi-photon generation for efficient quantum information processing
• The Oxford Questions on the foundations of quantum physics
• Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting Zeeman degeneracy
• Gouy Phase Radial Mode Sorter for Light: Concepts and Experiments
• Testing Bell's Inequality with Cosmic Photons: Closing the Setting-Independence Loophole
• Testing foundations of quantum mechanics with photons
• Highly efficient entanglement swapping and teleportation at telecom wavelength
• Heralded single photons based on spectral multiplexing and feed-forward control
• Interference of Identical Particles from Entanglement to Boson-Sampling
• Entanglement-enhanced quantum metrology: from standard quantum limit to Heisenberg limit
• Multiphoton Quantum-State Engineering using Conditional Measurements
• Entanglement-Based Quantum Information Technology
• Quantum Indistinguishability by Path Identity: The awakening of a sleeping beauty
• Recent advances for quantum classifiers
• Quantum memory and gates using a Lambda-type quantum emitter coupled to a chiral waveguide
• Four-photon orbital angular momentum entanglement
• Quantum interference between light sources separated by 150 million kilometers
• Flexible resources for quantum metrology
• Coherently driving a single quantum two-level system with dichromatic laser pulses
• Nonreciprocal enhancement of remote entanglement between nonidentical mechanical oscillators
• Hong-Ou-Mandel interferometry on a biphoton beat note
• Demonstration of active routing of entanglement in a multi-user network
• Generation of non-classical light in a photon-number superposition
• Computer-inspired Quantum Experiments
• Requirements for a loophole-free photonic Bell test using imperfect setting generators
• Pulsed Sagnac polarization-entangled photon source with a PPKTP crystal at telecom wavelength
• Observation of genuine three-photon interference
• Imaging of optically active defects with nanometer resolution
• Computer-inspired concept for high-dimensional multipartite quantum gates
• Highly efficient heralding of entangled single photons
• General rules for bosonic bunching in multimode interferometers
• Multiboson Correlation Interferometry with arbitrary single-photon pure states
• Generation and Detection of Atomic Spin Entanglement in Optical Lattices
• Quantum logic and entanglement by neutral Rydberg atoms: methods and fidelity
• Quantum state fusion in photons
• Entangled Two-Photon Absorption by Atoms and Molecules: A Quantum Optics Tutorial
• Emulating anyonic fractional statistical behavior in a superconducting quantum circuit
• Experimental progress on quantum coherence: detection, quantification, and manipulation
• An on-chip coupled resonator optical waveguide single-photon buffer
• Full analysis of multi-photon pair effects in spontaneous parametric down conversion based photonic quantum information processing
• Entanglement of Polarization and Orbital Angular Momentum
• Entanglement of Identical Particles and the Detection Process
• Sequential generation of multiphoton entanglement with a Rydberg superatom
• Multiphoton interference in quantum Fourier transform circuits and applications to quantum metrology
• Tomography of Ultra-relativistic Nuclei with Polarized Photon-gluon Collisions
• Compact engineering of path-entangled sources from a monolithic quadratic nonlinear photonic crystal
• Entangling Color-Different Photons via Time-Resolved Measurement and Active Feed-Forward
• Dissipative Quantum Metrology with Spin Cat States
• Fundamental building block for all-optical scalable quantum networks
• Scalable generation of multi-photon entangled states by active feed-forward and multiplexing
• Hanbury Brown and Twiss Interferometry with Twisted Light
• Observation of Ten-photon Entanglement Using Thin BiB${}_3$O${}_6$ Crystals
• High-yield fabrication of entangled photon emitters for hybrid quantum networking using high-temperature droplet epitaxy
• Quantum Experiments and Graphs II: Quantum Interference, Computation and State Generation
• Hierarchical Joint Remote State Preparation in Noisy Environment
• Simple preparation of Bell and GHZ states using ultrastrong-coupling circuit QED
• On-chip multiplexed multiple entanglement sources in a single silicon nanowire
• Generation of two-giant-atom entanglement in waveguide-QED systems
• Rydberg superatoms: An artificial quantum system for quantum information processing and quantum optics
• Young's double slit interference pattern from a twisted beam
• Near-unity indistinguishability single photon source for large-scale integrated quantum optics
• Topological photonics: fundamental concepts, recent developments, and future directions
• Tunable source of correlated atom beams
• No Return to Classical Reality
• Rydberg Quantum Gates Free from Blockade Error
• Emission-frequency separated high quality single-photon sources enabled by phonons
• Storage of hyperentanglement in a solid-state quantum memory
• Generation of Bell and GHZ states from a hybrid qubit-photon-magnon system
• Conceptual understanding through efficient inverse-design of quantum optical experiments
• Temporal and spectral manipulations of correlated photons using a time-lens
• Enhanced magnetic sensitivity with non-gaussian quantum fluctuations
• Probing quantum correlations in many-body systems: a review of scalable methods
• Nearly Deterministic Bell Measurement for Multiphoton Qubits and Its Application to Quantum Information Processing
• From the Physics to the Computational Complexity of Multiboson Correlation Interference
• Ultra-bright single photon source based on an atomically thin material
• A source of entangled photons based on a cavity-enhanced and strain-tuned GaAs quantum dot
• Secure Quantum Secret Sharing without Signal Disturbance Monitoring
• Quantum teleportation of physical qubits into logical code-spaces
• Benchmarking photon number resolving detectors
• Quantum NETwork: from theory to practice
• Quantum fluctuations and coherence in high-precision single-electron capture
• Efficient generation of twin photons at telecom wavelengths with 10 GHz repetition-rate tunable comb laser
• Direct generation of time-energy-entangled W triphotons in atomic vapor
• Cross-correlation between photons and phonons in quadratically coupled optomechanical systems
• Tunable two-photon quantum interference of structured light
• To freeze or not to: Quantum correlations under local decoherence
• Fundamental phenomena of quantum mechanics explored with neutron interferometers
• Generalized Geometric Measure of Entanglement for Multiparty Mixed States
• Hong-Ou-Mandel Interference between Two Deterministic Collective Excitations in an Atomic Ensemble
• All Multiparty Quantum States Can Be Made Monogamous
• Phase-imprinted multiphoton subradiant states
• Spin-based single-photon transistor, dynamic random access memory, diodes and routers in semiconductors
• Characterization of quantum correlations with local dimension constraints and its device-independent applications
• Bell Inequalities for Quantum Optical Fields
• Direct generation of frequency-bin entangled photons via two-period quasi-phase-matched parametric downconversion
• Interference of Temporally Distinguishable Photons Using Frequency-Resolved Detection
• Topological quantum transport and spatial entanglement distribution via disordered bulk channel
• Three-Photon Discrete-Energy-Entangled W State in Optical Fiber
• Experimental multi-location remote state preparation
• Multipartite Entanglement Accumulation in Quantum States: Localizable Generalized Geometric Measure
• Atomtronic protocol designs for NOON states
• Photonic graph state generation from quantum dots and color centers for quantum communications
• Manipulation of two-photon fluorescence spectra of chromophore aggregates with entangled photons: A simulation study
• Reducing $g^{(2)}(0)$ of a parametric down-conversion source via photon-number resolution with superconducting nanowire detectors
• Multiplexed entangled photon sources for all fiber quantum networks
• Interfering distinguishable photons
• Quantum interferometers: principles and applications
• On Chip Manipulation of Single Photons from a Diamond Defect
• Quantum optics: Push-button photon entanglement
• Two-photon interference from a quantum dot--microcavity: Persistent pure-dephasing and suppression of time-jitter
• Single pairs of time-bin entangled photons
• Multipartite entanglement detection with minimal effort
• Continuous-variable entanglement distillation over a pure loss channel with multiple quantum scissors
• Measurement-based entanglement of noninteracting bosonic atoms
• Extended linear regime of cavity-QED enhanced optical circular birefringence induced by a charged quantum dot
• Non-Gaussian Precision Metrology via Driving through Quantum Phase Transitions
• Path-controlled time reordering of paired photons in a dressed three-level cascade
• Experimental Generation of Spin-Photon Entanglement in Silicon Carbide
• Thermal-noise-resistant optomechanical entanglement via general dark-mode control
• Resource-efficient analyzer of Bell and Greenberger-Horne-Zeilinger states of multiphoton systems
• Near-deterministic hybrid generation of arbitrary photonic graph states using a single quantum emitter and linear optics
• Realization of a Universal Quantum Gate Set for Itinerant Microwave Photons
• Entanglement engineering and topological protection by discrete-time quantum walks
• Antibunched photon-pair source based on photon blockade effect in a nondegenerate optical parametric oscillator
• Probe optimization for quantum metrology via closed-loop learning control
• Nonlinear fluctuations and dissipation in matter revealed by quantum light
• Phonon-induced enhancement of photon entanglement in quantum dot-cavity systems
• Entanglement filter with Rydberg atoms
• Quantum internet using code division multiple access
• High visibility time-energy entangled photons from a silicon nanophotonic chip
• Observation of quasiparticle pair-production and quantum entanglement in atomic quantum gases quenched to an attractive interaction
• Two-particle interference of electron pairs on a molecular level
• Two-Photon Excitation Sets Limit to Entangled Photon Pair Generation from Quantum Emitters
• Generation and Eight-port Homodyne Characterization of Time-bin Qubits for Continuous-variable Quantum Information Processing
• Testing higher-order quantum interference with many-particle states
• Towards On-Demand Heralded Single-Photon Sources via Photon Blockade
• Phase-Matching Quantum Cryptographic Conferencing
• Shaping field correlations with quantum antennas
• Two-photon interference of temporally separated photons
• Giant Kerr nonlinearities and magneto-optical rotations in a Rydberg-atom gas via double electromagnetically induced transparency
• Quantum speed limit of a photon under non-Markovian dynamics
• Towards scalable entangled photon sources with self-assembled InAs/GaAs quantum dots
• Do Large Number of Parties Enforce Monogamy in All Quantum Correlations?
• Exciton-Enhanced Spontaneous Parametric Down-Conversion in Two-Dimensional Crystals
• Universal quantum multi-qubit entangling gates with auxiliary spaces
• Scientific intuition inspired by machine learning generated hypotheses
• Non post-selected indistinguishable single photons generated by a quantum dot under resonant excitation
• Theory of filtered type-II PDC in the continuous-variable domain: Quantifying the impacts of filtering
• Semi-Deterministic Entanglement between a Single Photon and an Atomic Ensemble
• Quantum steering inequality with tolerance for measurement-setting-errors: experimentally feasible signature of unbounded violation
• Quantum interference of resonance fluorescence from Germanium-vacancy color centers in diamond
• Efimov States of Strongly Interacting Photons
• Experimental Observation of Earth's Rotation with Quantum Entanglement
• Deterministic generation of bright single resonance fluorescence photons from a Purcell-enhanced quantum dot-micropillar system
• Detecting genuine multipartite entanglement of pure states with bipartite correlations
• High-Dimensional Entanglement for Quantum Communication in the Frequency Domain
• Generation of a frequency-degenerate four-photon entangled state using a silicon nanowire
• Entangling three qubits without ever touching
• Two-Particle Interference with Double Twin-Atom Beams
• Entanglement Witnesses and Measures for Bright Squeezed Vacuum
• Exclusion Principle for Quantum Dense Coding
• Quantum Computer-Aided design of Quantum Optics Hardware
• Digital Discovery of 100 diverse Quantum Experiments with PyTheus
• Intrinsic and environmental effects on the interference properties of a high-performance quantum dot single photon source
• Resonance fluorescence spectral dynamics of an acoustically modulated quantum dot
• Multiplexed spin-wave-photon entanglement source using temporal-multimode memories and feedforward-controlled readout
• Helicity sensitive plasmonic teraherts interferometer
• Ultrabright Entanglement Based Quantum Key Distribution over a 404 km Optical Fiber
• Exploration of photon-number entangled states using weak nonlinearities
• Multi-Boson Correlation Sampling
• Hybrid quantum-classical approach to enhanced quantum metrology
• Hong-Ou-Mandel Interference between Two Hyper-Entangled Photons Enables Observation of Symmetric and Anti-Symmetric Particle Exchange Phases
• Quantum information
• Loss-tolerant all-photonic quantum repeater with generalized Shor code
• Photonic multipartite entanglement conversion using nonlocal operations
• Learning Interpretable Representations of Entanglement in Quantum Optics Experiments using Deep Generative Models
• Experimental Demonstration of Robust Bidirectional Quantum Optical Communications
• Experimental Demonstration of Instrument-specific Quantum Memory Effects and Non-Markovian Process Recovery for Common-Cause Processes
• From strong to weak temperature dependence of the two-photon entanglement resulting from the biexciton cascade inside a cavity
• A high visibility Hong-Ou-Mandel interference via a time-resolved coincidence measurement
• Experimental high fidelity six-photon entangled state for telecloning protocols
• Efficient detection of a highly bright photon source using superconducting nanowire single photon detectors
• Non-linear two-photon resonance fluorescence on a single artificial atom
• Greenberger-Horne-Zeilinger theorem for N qudits
• Experimental violation of Bell inequalities for multi-dimensional systems
• Observation of intensity squeezing in resonance fluorescence from a solid-state device
• Heralded Generation of Macroscopic Superposition States in a Spinor Bose-Einstein Condensate
• Multipath Correlation Interference and Controlled-NOT Gate Simulation with a Thermal Source
• Narrowband Biphotons with Polarization-Frequency Coupled Hyperentanglement
• Multi-setting Greenberger-Horne-Zeilinger theorem
• Many-particle interference to test Born's rule
• Dynamical learning of a photonics quantum-state engineering process
• Localization of relativistic particles and uncertainty relations
• Detection-dependent six-photon NOON state interference
• Polarization dependent light-matter coupling and highly indistinguishable resonance fluorescence photons from quantum dot-micropillar cavities with elliptical cross-section
• Symmetries and entanglement features of inner-mode resolved correlations of interfering nonidentical photons
• Entangling time-bin qubits with a switch
• Twin photon pairs in a high-Q silicon microresonator
• Frequency Feedback for Two-Photon Interference from Separate Quantum Dots
• Sudden change of geometric quantum discord in finite temperature reservoirs
• Preparation of multiphoton high-dimensional GHZ state
• Revival of Quantum Interference by Modulating the Biphotons
• Repeater-like asynchronous measurement-device-independent quantum conference key agreement
• Growth of genuine multipartite entanglement in random unitary circuits
• Quantum Conference
• Recent advances in high-dimensional mode-locked quantum frequency combs
• High production rate of single-photon and two-photon Fock states for quantum state engineering
• Quantum Communication using Code Division Multiple Access Network
• Quantum optical coherence: From linear to nonlinear interferometers
• Highly efficient and indistinguishable single-photon sources via phonon-decoupled two-color excitation
• Nearly deterministic Bell measurement with multiphoton entanglement for efficient quantum information processing
• Overcoming correlation fluctuations in two-photon interference experiments with differently bright and independently blinking remote quantum emitters
• Characterization of two distant double-slits by chaotic light second-order interference
• Dressed-state analysis of two-color excitation schemes
• Robust Self-Testing of Multiparticle Entanglement
• Single-mode fiber coupling with a M-SPGD algorithm for long-range quantum communications
• Influence of quantum dot geometry on p-shell transitions in differently charged quantum dots
• Modulation of single-photon-level wave packets with two-component electromagnetically induced transparency
• Interference contrast in multi-source few photon optics
• Relativistic frame-dragging and the Hong-Ou-Mandel dip $-$ a primitive to gravitational effects in multi-photon quantum-interference
• Remote entanglement distribution in a quantum network via multinode indistinguishability of photons
• Quantifying Quantum-Mechanical Processes
• Direct method for measuring and witnessing quantum entanglement of arbitrary two-qubit states through Hong-Ou-Mandel interference
• Generation of narrow-band polarization-entangled photon pairs at a rubidium D1 line
• Experimental Test of Relation between Coherence and Path Information
• Entangling two microwave modes via optomechanics
• Unified quantum density matrix description of coherence and polarization
• Deterministic single-atom source of quasi-superradiant $N$-photon pulses
• Quantum Process Capability
• Efficient Measurement of Multiparticle Entanglement with Embedding Quantum Simulator
• Optical Phase Measurement Using a Deterministic Source of Entangled Multi-photon States
• Single-photon interference over 8.4 km urban atmosphere: towards testing quantum effects in curved spacetime with photons
• Measuring nonclassical correlations of two-photon states
• Beyond the four-level model: Dark and hot states in quantum dots degrade photonic entanglement
• Design of quantum optical experiments with logic artificial intelligence
• Generating NOON states in circuit QED using multi-photon resonance in the presence of counter-rotating interactions
• Photon-pair generation in photonic crystal fibrebre with a 1.5GHz modelocked VECSEL
• Cloning of Quantum Entanglement
• Normalized Stokes operators for polarization correlations of entangled optical fields
• A Scanning 2-Grating Free Electron Mach-Zehnder Interferometer
• Temporally versatile polarization entanglement from Bragg-reflection waveguides
• Spin- and Momentum-Correlated Atom Pairs Mediated by Photon Exchange and Seeded by Vacuum Fluctuations
• Many-Particle Interferometry and Entanglement by Path Identity
• Simulating the Dynamics of Single Photons in BosonSampling Devices with Matrix Product States
• Measuring Entanglement in a Photonic Embedding Quantum Simulator
• Persistency of non-n-local correlations in noisy linear networks
• Designing Robust Quantum Refrigerators in Disordered Spin Models
• Quantum repeaters based on atomic ensembles and linear optics
• Optimal conditions for Bell test using spontaneous parametric down-conversion sources
• Deterministic Quantum Dense Coding Networks
• Two-photon interference of polarization-entangled photons in a Franson interferometer
• Noise resistance of violation of local causality for pure three-qutrit entangled states
• Measuring entanglement of photons produced by a pulsed source
• Signatures of Many-Particle Interference
• Genuine multipartite nonlocality with causal-diagram postselection
• Quantum metrology enhanced by coherence-induced-driving in a cavity QED setup
• Entanglement swapping with energy-polarization entangled photons from quantum dot cascade decay
• Experimental demonstration of genuine tripartite nonlocality under strict locality conditions
• Local versus Global Two-Photon Interference in Quantum Networks
• N-particle nonclassicality without N-particle correlations
• Scale-invariant freezing of entanglement
• Entangling two giant atoms via a topological waveguide
• Higher Order Mode Entanglement in a Type II Optical Parametric Oscillator
• Phase-stable source of high-quality three-photon polarization entanglement by cascaded downconversion
• Extending the Hong-Ou-Mandel Effect: the power of nonclassicality
• Simultaneous generation of two spin-wave-photon entangled states in an atomic ensemble
• Measurement of magic-wavelength optical dipole trap by using the laser-induced fluorescence spectra of trapped single cesium atoms
• Efficient linear optical generation of a multipartite W state
• One-shot conclusive multiport quantum dense coding capacities
• Generation of a time-bin Greenberger--Horne--Zeilinger state with an optical switch
• Graphene as a source of entangled plasmons
• Reducing Computational Complexity of Quantum Correlations
• Entangled state generation with an intrinsically pure single-photon source and a weak coherent source
• Parametric down conversion with a depleted pump as a model for classical information transmission capacity of quantum black holes
• Spectral characterization of photon-pair sources via classical sum-frequency generation
• True Multipartite Entanglement Hardy Test
• Interference of macroscopic beams on a beam splitter: phase uncertainty converted into photon-number uncertainty
• Conservation of angular momentum on a single-photon level
• Highly efficient source for frequency-entangled photon pairs generated in a 3rd order periodically poled MgO-doped stoichiometric LiTaO3 crystal
• High-dimensional quantum encoding via photon-subtracted squeezed states
• Limits to multipartite entanglement generation with bosons and fermions
• Enhancing robustness of multiparty quantum correlations using weak measurement
• Detecting the dimensionality of genuine multi-particle entanglement
• Optimal interferometry for Bell$-$nonclassicality by a vacuum$-$one$-$photon qubit
• Directional subradiance from helical-phase-imprinted multiphoton states
• Witnessing negativity of Wigner function by estimating fidelities of cat-like states from homodyne measurements
• Compact Bell inequalities for multipartite experiments
• Multi-photon nonclassical correlations in entangled squeezed vacuum states
• Proposal for distribution of multi-photon entanglement with optimal rate-distance scaling
• The first- and second-order temporal interference between thermal and laser light
• Experimental Test of Irreducible Four-Qubit Greenberger-Horne-Zeilinger Paradox
• Nonclassical correlated deterministic single-photon pairs for a trapped atom in bimodal cavities
• Cascaded cold atomic ensembles in a diamond configuration as a spectrally entangled multiphoton source
• Preparation and purification of four-photon Greenberger-Horne-Zeilinger state
• Dipole-Coupled Defect Pairs as Deterministic Entangled Photon Pair Sources
• Optical Detection and Storage of Entanglement in Plasmonically Coupled Quantum Dot Qubits
• The inflation hierarchy and the polarization hierarchy are complete for the quantum bilocal scenario
• Measurement of photon correlations with multipixel photon counters
• Engineering Arbitrary Hamiltonians in Phase Space
• Designing refrigerators in higher dimensions using quantum spin models
• Programmable coherent linear quantum operations with high-dimensional optical spatial modes
• Experimental Measurement-Device-Independent Quantum Cryptographic Conferencing
• Constructive Simulation and Topological Design of Protocols
• Hyper-entanglement between pulse modes and frequency bins
• Four-Photon GHZ Entanglement via Collective Two-Photon Coherence in Doppler-Broadened Atoms
• Measurement-Induced Entanglement Phase Transition in Free Fermion Systems
• Fourier processing of quantum light
• Effect of incoherent pump on two-mode entanglement in optical parametric generation
• Topologically Protected Quantum Entanglement
• Joining and splitting the quantum states of photons
• Coherent states of the Laguerre-Gauss modes
• Entanglement distribution over quantum code-division-multiple-access networks
• Two Copies of the Einstein-Podolsky-Rosen State of Light Lead to Refutation of EPR Ideas
• Linear-Optic Heralded Photon Source
• Scattershot multiboson correlation sampling with random photonic inner-mode multiplexing
• Simulating arbitrary Gaussian circuits with linear optics
• Certification of Genuine Multipartite Entanglement with General and Robust Device-independent Witnesses
• Two-photon excitation with finite pulses unlocks pure dephasing-induced degradation of entangled photons emitted by quantum dots
• Determinism, independence and objectivity are incompatible
• Quantum many-body simulation using monolayer exciton-polaritons in coupled-cavities
• Phase conjugation and mode conversion in stimulated parametric down-conversion with orbital angular momentum: a geometrical interpretation
• Optimized state independent entanglement detection based on geometrical threshold criterion
• Certifying Quantum Temporal Correlation via Randomized Measurements: Theory and Experiment
• Many-body quantum lock-in amplifier
• Polarization and Orbital Angular Momentum Encoded Quantum Toffoli Gate Enabled by Diffractive Neural Networks
• Improving the performance of quantum approximate optimization for preparing non-trivial quantum states without translational symmetry
• Heralded preparation of polarization entanglement via quantum scissors
• Taming numerical errors in simulations of continuous variable non-Gaussian state preparation
• Aperiodic bandgap structures for enhanced quantum two-photon sources
• Distance sensing emerging from second-order interference of thermal light
• Absolute separability witnesses for symmetric multiqubit states
• Rating the performance of noisy teleportation using fluctuations in fidelity
• Introduction to gravitational redshift of quantum photons propagating in curved spacetime
• Effect of long-range interactions on multipartite entanglement in Heisenberg chains
• On-Chip Multiphoton Entangled States by Path Identity
• Dicke States Generation via Selective Interactions in Dicke-Stark Model
• Partitioning dysprosium's electronic spin to reveal entanglement in non-classical states
• Heralded generation of Bell states using atomic ensembles
• Synchronization and phase shaping of single photons with high-efficiency quantum memory
• Photon-pair blockade in a Josephson-photonics circuit with two nondegenerate microwave resonators
• Distinguishability in quantum interference with the squeezed states
• Monogamy relations of all quantum correlation measures for multipartite quantum systems
• Towards Quantum Repeaters with Solid-State Qubits: Spin-Photon Entanglement Generation using Self-Assembled Quantum Dots
• The persistence of spin coherence in a crystalline environment
• Eliminating temporal correlation in quantum-dot entangled photon source by quantum interference
• Electromagnetic fields, size, and copy of a single photon
• Quantum interference between non-identical single particles
• All-optical tailoring of single-photon spectra in a quantum-dot microcavity system
• Violation of generalized Bell inequality and its optimal measurement settings
• Maximum entanglement of mixed symmetric states under unitary transformations
• Active Temporal Multiplexing of Photons
• Entanglement of Nambu Spinors and Bell Inequality Test Without Beam Splitters
• Tomographic characterisation of correlations in a photonic tripartite state
• Symmetric quantum states: a review of recent progress
• Observation of two-photon interference effect with single non-photon-number resolving detector
• Two methods for measuring Bell nonlocality via local unitary invariants of two-qubit systems in Hong-Ou-Mandel interferometers
• Geometric chained inequalities for higher-dimensional systems
• Different types of photon entanglement from a constantly driven quantum emitter inside a cavity
• Harnessing spontaneous emission of correlated photon pairs from ladder-type giant atoms
• Collateral coupling between superconducting resonators: Fast and high fidelity generation of qudit-qudit entanglement
• Violating Bell inequality using weak coherent states
• Fault-tolerant syndrome extraction and cat state preparation with fewer qubits
• Swapping Intra-photon entanglement to Inter-photon entanglement using linear optical devices
• Entanglement and non-locality in quantum protocols with identical particles
• A High-Finesse Suspended Interferometric Sensor for Macroscopic Quantum Mechanics with Femtometre Sensitivity
• Scalable Bell inequalities for multiqubit systems
• Scalable quantum information transfer between nitrogen-vacancy-center ensembles
• Wavelength conversion for single-photon polarization qubits through continuous variable quantum teleportation
• Performance of the nanopost single-photon source: beyond the single-mode model
• Squeezed gravitons from superradiant axion fields around rotating black holes
• Quantum interface between frequency-uncorrelated down-converted entanglement and atomic-ensemble quantum memory
• Rebuilding of destroyed spin squeezing in noisy environments
• Schmidt-number benchmarks for continuous-variable quantum devices
• Photonic realization of quantum resetting
• Time-bin entanglement in the deterministic generation of linear photonic cluster states
• Polarized indistinguishable single photons from a quantum dot in an elliptical micropillar
• Role of indistinguishability and entanglement in Hong-Ou-Mandel interference and finite bandwidth effects of frequency entangled photons
• Arbitrary entanglement of three qubits via linear optics
• Verification of Bell Nonlocality by Violating Quantum Monogamy Relations
• Propagation-invariant high-dimensional orbital angular momentum states
• Modeling of quasi-phase-matched cavity enhanced second harmonic generation
• Vector Properties of Entanglement in a Three-Qubit System
• Quantifying entanglement preservability of experimental processes
• Non-classicality of bright GHZ-like radiation of an optical parametric source
• How efficient is transport of quantum cargo through multiple highways?
• Statistical limits for quantum networks with semiconductor entangled photon sources
• Experimental self-testing for photonic graph states
• A Quantum Optical Microphone in the Audio Band
• Superiority in dense coding through non-Markovian stochasticity
• Complete spectral characterization of biphotons by simultaneously determining its frequency sum and difference in a single quantum interferometer
• Quantum and Classical Two-photon Interference of Single Photons with Ultralong Coherence Time
• Low-loss polarization-maintaining router for single and entangled photons at a telecom wavelength
• Correlation-based entanglement criterion in bipartite multiboson systems
• Continuously tunable single-photon level nonlinearity with Rydberg state wave-function engineering
• Low-Loss Polarization-Maintaining Optical Router for Photonic Quantum Information Processing
• Device-independent Verification of Quantum Coherence without Quantum Control
• Sine wave gating Silicon single-photon detectors for multiphoton entanglement experiments
• Multi-photon quantum interference with high visibility using multiport beam splitters
• Violations of entropic Bell inequalities with coarse-grained quadrature measurements for continuous-variable states
• Correlations of cascaded photons: An analytical study in the two-photon Mollow regime
• Photonic quantum simulation of ground state configurations of Heisenberg square and checkerboard lattice spin systems
• Remote state preparation by multiple observers using a single copy of a two-qubit entangled state
• A nonlocal polarization interferometer for entanglement detection
• Interfacing a two-photon NOON state with an atomic quantum memory
• Nonmaximally entangled states can be better for quantum correlation distribution and storage
• Hong-Ou-Mandel Interference in a temporal-average-inversion-symmetric chain
• Scaling Enhancement of Photon Blockade in Output Fields
• Three-particle quantum correlation interferometry
• Scalable Determination of Multipartite Entanglement in Quantum Networks
• General mapping of multi-qu$d$it entanglement conditions to non-separability indicators for quantum optical fields
• Coarse-grained spectral projection (CGSP): a deep learning-assisted approach to quantum unitary dynamics
• Control and enhancement of interferometric coupling between two photonic qubits
• Scalable symmetry detector and its applications by using beam splitters and weak nonlinearities
• Experimental characterization of a non-local convertor for quantum photonic networks
• Hong-Ou-Mandel effect in terms of the temporal biphoton wave function with two arrival-time variables
• Bunching Effect and Quantum Statistics of Partially Indistinguishable Photons
• Time-dependent switching of the photon entanglement type using a driven quantum emitter-cavity system
• Quantum gate description for induced coherence without induced emission and related phenomena
• Berry phase and the Mandel parameter of the non-degenerate parametric amplifier
• Deterministic single-photon source in the ultrastrong coupling regime
• Which role does multiphoton interference play in small phase estimation in quantum Fourier transform interferometers?
• Quantum synchronization in an all-optical stroboscopic quantum simulator
• Reversed interplay of quantum interference and which-way information in multi-photon entangled states
• Tripartite multiphoton Jaynes-Cummings model: Analytical solution and Wigner nonclassicalities
• Experimental characterization of photon-number noise in Rarity-Tapster type interferometers
• Phonon-induced transition between entangled and nonentangled photon emission in constantly driven quantum-dot--cavity systems
• Digital Discovery of a Scientific Concept at the Core of Experimental Quantum Optics
• Interactive Entanglement in Hybrid Opto-magno-mechanics System
• Electrically-Pumped Wavelength-Tunable GaAs Quantum Dots Interfaced with Rubidium Atoms
• Reconstruction of Quantum Particle Statistics: Bosons, Fermions, and Transtatistics
• Observation of quantum nonlocality in Greenberger-Horne-Zeilinger entanglement on a silicon chip
• Spectral compression and entanglement reduction in the cascaded biphoton state with cavities
• Two-mode correlated multiphoton bundle emission
• Discrimination strategies for inequivalent classes of multipartite entangled states
• Questions on the Structure of Perfect Matchings inspired by Quantum Physics
• Geometric extension of Clauser-Horne inequality to more qubits
• Multi-Path and Multi-Particle Tests of Complex vs. Hyper-Complex Quantum Theory
• Quantum walks and entanglement in cavity networks
• Protecting temporal correlations of two-qubit states using quantum channels with memory
• Clearer visibility Hong-Ou-Mandel effect with correlation function based on rates rather than intensities
• Fast atom-photon entangling gates with a superconducting coplanar waveguide
• Two-photon spin states and entanglement states
• Photo-Thermally Tunable Photon-Pair Generation in Dielectric Metasurfaces
• Super sensitivity and super resolution with quantum teleportation
• Serial-parallel conversion for single photons with heralding signals
• Flexible and experimentally feasible shortcut to quantum Zeno dynamic passage
• Feasible quantum engineering of quantum multiphoton superpositions
• Quantum Coherence and Distinguishability as Complementary Resources: A Resource-Theoretic Perspective from Wave-Particle Duality
• Monogamy-of-entanglement-inspired protocol to quantify bipartite entanglement using spin squeezing
• Precisely resolve energy-time entanglement by dual channel Fabry-Perot interferometry
• Detecting single photons is not always necessary to evidence interference of photon probability amplitudes
• Quantum Interference in Atomic Systems
• Genuine monogamy relations in no-signaling theories - a geometric approach
• Zero-threshold correlated-photon laser with a single trapped atom in a bimodal cavity
• Kerr-enhanced optomechanical entanglement generation via reservoir design
• Frequency-Bin Entanglement with Tunable Phase
• Distribution of entanglement with variable range interactions
• Controlled emission of entangled multiphoton states from cascaded quantum wells
• Quantifying interference in multipartite quantum systems
• Resonance fluorescence from an atomic-quantum-memory compatible single photon source based on GaAs droplet quantum dots
• Three-Photon Polarization Entanglement of Green Light
• Interference in Quantum Mechanics
• Entanglement robustness to excitonic spin precession in a quantum dot
• Measurement-Disturbance Tradeoff Outperforming Optimal Cloning
• Entanglement indicators for quantum optical fields: three-mode multiport beamsplitters EPR interference experiments
• Coherent quantum dynamics of systems with coupling-induced creation pathways
• Interference between distinguishable photons
• Twin GHZ-states behave differently
• Entanglement Meter: Estimation of entanglement with single copy in Interferometer
• Threefold Way for Typical Entanglement
• Precision of the acoustic control of single photon scattering with semiconductor quantum dots
• Adding Photonic Entanglement to Superradiance by Using Multilevel Atoms
• Universal Entanglement and an Information-Complete Quantum Theory
• Quantum Phase Imaging using Spatial Entanglement
• Ultra-broadband spectral and polarisation entanglement using dispersion-engineered nanophotonic waveguides
• Incoherent control of two-photon induced optical measurements in open quantum systems: quantum heat engine perspective
• Non-Abelian interference of topological edge states
• Optimal filtering and generation of entangled photons for quantum applications in the presence of noise
• Experimental Quantum Channel Purification
• Tripartite State Characterization via Activated Bipartite Entanglement
• Multisetting Bell inequalities for $N$ spins-1 avoiding KS contradiction
• Quantum walk on a square lattice with identical particles
• Entangled photons from composite cascade emitters
• Entanglement conditions involving intensity correlations of optical fields: the case of multi-port interferometry
• Manipulation of tripartite-to-bipartite entanglement localization under quantum noises and its application to entanglement distribution
• Collective unitary evolution with linear optics by Cartan decomposition
• Room Temperature Continuous-wave Excited Biexciton Emission in CsPbBr3 Nanocrystals
• On the connection between quantum nonlocality and phase sensitivity of two-mode entangled Fock state superpositions
• Hanbury Brown and Twiss interference of electrons in free space from independent needle tip sources
• Entangled-photon interferometry for plasmas
• Recycling the resource: Sequential usage of shared state in quantum teleportation with weak measurements
• Interference and wave-particle duality of single photons
• On safe post-selection for Bell tests with ideal detectors: Causal diagram approach
• Gaussian state entanglement witnessing through lossy compression
• Conditional states and entropy in qudit-qubit systems
• Hong-Ou-Mandel interference of unconventional temporal laser modes
• Quantum coherent feedback control of an N-level atom with multiple excitations
• Quantum correlation generation capability of experimental processes
• Gate Teleportation-based Universal Blind Quantum Computation
• Tunable single photon and two-photon emission in a four-level quantum dot-bimodal cavity system
• Experimental interference of uncorrelated photons
• A full characterization of the polarization of vector light beams
• Nonreciprocal photon bundle emission
• Semi-nonlinear nanophotonic waveguides for highly efficient second-harmonic generation
• On six-photon entangled state emitted from a single third-order parametric down-conversion process
• Creating two-qudit maximally entangled quantum link through bulk
• Coincidence detection techniques for direct measurement of many-body correlations in strongly correlated electron systems
• Open dynamics of entanglement in mesoscopic bosonic systems
• Renormalization and small-world model of fractal quantum repeater networks
• Entanglement Superactivation in Multiphoton Distillation Networks
• Does Quantum Information Require Additional Structure?
• Imperfect Entangling Power of Quantum Gates
• Hong-Ou-Mandel interference between two independent all fiber photon sources
• A vapor-cavity-QED system for quantum computation and communication
• Phase and Photon Number Dependent NOON State Localization in Flat Band Lattices
• Photonic quantum information with time-bins: Principles and applications
• Generating quantum non-local entanglement with mechanical rotations
• Bosonic fields in states with undefined particle numbers possess detectable non-contextuality features, plus more
• Optimal randomized measurements for a family of non-linear quantum properties
• Entanglement dynamics of two modes coupled through a dissipative movable mirror in an optomechanical system
• Energy-tunable entangled photon sources on a III-V/Silicon chip
• Minimum Number of Copies in the Measurement of Multi-Photon Entanglement
• Experimental generation of tripartite telecom photons via an atomic ensemble and a nonlinear waveguide
• Hyperentanglement-enhanced Weak Value Amplification with High-Order Correlation Function
• Quantum teleportation of multiple properties of a single quantum particle
• Interference of interference effects
• Are vector vortex beams endowed with any entanglement?
• Tunable cavity-enhanced photon pairs source in Hermite-Gaussian mode
• Design of Voltage Pulse Control Module for Free Space Measurement-Device-Independent Quantum Key Distribution
• Feasible logic Bell-state analysis with linear optics
• Emergence of Classical Objectivity of Quantum Darwinism in a Photonic Quantum Simulator
• Outperforming classical estimation of Post-Newtonian parameters of Earth's gravitational field using quantum metrology
• Different Types of Coherence: Young-type Interference versus Dicke Superradiance
• Experimental Test of Generalized Hardy's Paradox
• Generation and dynamical manipulation of polarization entangled Bell states by a silicon quantum photonic circuit
• Near-unity efficiency and photon indistinguishability for the "hourglass" single-photon source using suppression of background emission
• Topological phases and entanglement in real space for 1D SSH topological insulator: effects of first and second neighbor-hoppings
• Dissipative engineering a tripartite Greenberger-Horne-Zeilinger state for neutral atoms
• Generation of frequency entanglement by rotating Doppler effect