Measuring bipartite quantum correlations of an unknown state

Abstract

We report the experimental measurement of bipartite quantum correlations of an unknown two-qubit state. Using a liquid state Nuclear Magnetic Resonance (NMR) setup and employing geometric discord, we evaluate the quantum correlations of a state without resorting to prior knowledge of its density matrix. The method is applicable to any (2 x d) system and provides, in terms of number of measurements required, an advantage over full state tomography scaling with the dimension d of the unmeasured subsystem. The negativity of quantumness is measured as well for reference. We also observe the phenomenon of sudden transition of quantum correlations when local phase and amplitude damping channels are applied to the state.

5+2 pages, 3+1 figures. Published in PRL

References in corpus (45)

• A computable measure of entanglement
• Introducing Quantum Discord
• Classical, quantum and total correlations
• The classical-quantum boundary for correlations: discord and related measures
• NMR Techniques for Quantum Control and Computation
• Necessary and sufficient condition for non-zero quantum discord
• Experimental quantum computing without entanglement
• Robustness of quantum discord to sudden death
• Sudden transition between classical and quantum decoherence
• Classical and quantum correlations under decoherence
• Almost all quantum states have non-classical correlations
• Quantum discord as resource for remote state preparation
• Non-Markovian Dynamics of Quantum Discord
• Experimental investigation of classical and quantum correlations under decoherence
• Entanglement and the Power of One Qubit
• Interpreting quantum discord through quantum state merging
• Operational interpretations of quantum discord
• Linking Quantum Discord to Entanglement in a Measurement
• The problem with the geometric discord
• All non-classical correlations can be activated into distillable entanglement
• Operational Significance of Discord Consumption: Theory and Experiment
• Revival of quantum correlations without system-environment back-action
• An observable entanglement measure for unknown mixed quantum states
• Direct measurement of non-linear properties of bipartite quantum states
• Environment-induced sudden transition in quantum discord dynamics
• Observable measure of bipartite quantum correlations
• Theoretical and experimental aspects of quantum discord and related measures
• Experimentally Witnessing the Quantumness of Correlations
• Nonclassical correlation in NMR quadrupolar systems
• Interplay between computable measures of entanglement and other quantum correlations
• Detecting nonclassical system-environment correlations by local operations
• Quantum resources for hybrid communication via qubit-oscillator states
• Homodyne estimation of Gaussian quantum discord
• Experimental Investigation of the Evolution of Gaussian Quantum Discord in an Open System
• Analysis of Density Matrix reconstruction in NMR Quantum Computing
• Emergence of the pointer basis through the dynamics of correlations
• Necessary and sufficient conditions of freezing phenomena of quantum discord under phase damping
• Detecting the quantum discord of an unknown state by a single observable
• Witnessing nonclassical multipartite states
• Direct scheme for measuring the geometric quantum discord
• Thermal Equilibrium as an Initial State for Quantum Computation by NMR
• On the quantumness of correlations in nuclear magnetic resonance
• Classicality witness for two-qubit states
• Quantum discord in nuclear magnetic resonance systems at room temperature
• Theoretical insights on measuring quantum correlations

Cited by in corpus (49)

• Observable measure of quantum coherence in finite dimensional systems
• Measures and applications of quantum correlations
• Frozen Quantum Coherence
• Geometric quantum discord through the Schatten 1-norm
• Generalized Geometric Quantum Speed Limits
• Quantum discord and its allies: a review
• Genuine quantum correlations in quantum many-body systems: a review of recent progress
• Comparative investigation of the freezing phenomena for quantum correlations under nondissipative decoherence
• Negativity of quantumness and its interpretations
• One-norm geometric quantum discord under decoherence
• Observation of time-invariant coherence in a room temperature quantum simulator
• Quantum discord and steering in top quarks at the LHC
• Local Detection of Quantum Correlations with a Single Trapped Ion
• Hierarchy and dynamics of trace distance correlations
• Universal freezing of quantum correlations within the geometric approach
• Observation of environment-induced double sudden transitions in geometric quantum correlations
• Unifying approach to the quantification of bipartite correlations by Bures distance
• Quantum discord cannot be shared
• Experimental entanglement activation from discord in a programmable quantum measurement
• Observing optical coherence across Fock layers with weak-field homodyne detectors
• Geometric classical and total correlations via trace distance
• Experimental estimation of quantum discord for polarization qubit and the use of fidelity to assess quantum correlations
• Trace-distance correlations for X states and emergence of the pointer basis in Markovian and non-Markovian regimes
• Experimental detection of polarization-frequency quantum correlations in a photonic quantum channel by local operations
• Quantum correlation measure in arbitrary bipartite systems
• There is more to quantum interferometry than entanglement
• Single and double changes of Entanglement
• Entanglement detection on an NMR quantum information processor using random local measurements
• How to observe and quantify quantum-discorded states
• How to observe and quantify quantum-discorded states via correlations
• Sudden Freezing and Thawing of Entanglement Sharing in a Shrunken Volume
• Sudden transitions of trace distance discord of dipole-dipole coupled two qubits
• Non-Markovianity through Multipartite Correlation Measures
• No-activation theorem for Gaussian nonclassical correlations by Gaussian operations
• Entanglement and quantum teleportation via decohered tripartite entangled states
• Witnessing nonclassical correlations via a single-shot experiment on an ensemble of spins using NMR
• Negativity of quantumness and non-Markovianity in a qubit coupled to a thermal Ising spin bath system
• Schrödinger cat and Werner state disentanglement simulated by trapped ion systems
• Simulating the effect of weak measurements by a phase damping channel and determining different measures of bipartite correlations in nuclear magnetic resonance
• Correlation evolution and monogamy of two geometric quantum discords in multipartite systems
• Adiabatic freezing of long-range quantum correlations in spin chains
• The local detection method: Dynamical detection of quantum discord with local operations
• Computing coherence vectors and correlation matrices, with application to quantum discord quantification
• Quantum Discord Witness With Uncharacterized Devices
• Unified scheme for correlations using linear relative entropy
• Hierarchy of quantum correlations in qubit-qutrit axially symmetric states
• Complete condition for nonzero quantum correlation in continuous variable systems
• A showing of entangling and discording power for cooper-pair gate
• Geometric measure for two-qubit CS-states: an exactly solvable model