Violating the Leggett-Garg inequalities with classical light
arXiv:2009.02219 · doi:10.1103/PhysRevA.103.043707
Abstract
In an endeavour to better define the distinction between classical macroscopic and quantum microscopic regimes, the Leggett-Garg inequalities were established as a test of macroscopic-realistic theories, which are commonly thought to be a suitable class of descriptions for classical dynamics. The relationship between their violation and non-classicality is however not obvious. We show that classical states of light, which in the quantum optical sense are any convex sums of coherent states, may not satisfy the Leggett-Garg inequalities. After introducing a simple Mach-Zehnder setup and showing how to obtain a violation with a single photon using negative measurements, we focus on classical states of light, in particular those of low average photon number. We demonstrate how one can still perform negative measurements with an appropriate assignment of variables, and show that the inequalities are violable with coherent states. Finally, we abandon initial phase reference and demonstrate that the violation is still possible, in particular with thermal states of light, and we investigate the effect of intermediate dephasing.
arXiv comment-Minor changes in abstract and introduction. -Added a comprehensive table with all possible cases for clarity. -Corrected result for thermal state. 10 pages, 5 figures
References in corpus (38)
- Advances in Quantum Metrology
- Quantum-enhanced measurements: beating the standard quantum limit
- Quantum metrology
- Decoherence, the measurement problem, and interpretations of quantum mechanics
- Quantum Computing
- Operational Resource Theory of Coherence
- Quantum Mechanical Interaction-Free Measurements
- Contextuality for preparations, transformations, and unsharp measurements
- Preserving coherence in quantum computation by pairing quantum bits
- Leggett-Garg Inequalities
- Converting Coherence to Quantum Correlations
- Efficient Quantum Computation using Coherent States
- Witnessing Quantum Coherence: from solid-state to biological systems
- Violation of the Leggett-Garg inequality with weak measurements of photons
- Coherence as a resource in decision problems: The Deutsch-Jozsa algorithm and a variation
- Experimental Violation of Two-Party Leggett-Garg Inequalities with Semi-weak Measurements
- Condition for macroscopic realism beyond the Leggett-Garg inequalities
- Ideal negative measurements in quantum walks disprove theories based on classical trajectories
- Nonclassicality as a Quantifiable Resource for Quantum Metrology
- A resource theory of superposition
- No Fine theorem for macrorealism: Limitations of the Leggett-Garg inequality
- Violation of Leggett-Garg inequalities in quantum measurements with variable resolution and back-action
- Simulation of quantum random walks using interference of classical field
- Operational resource theory of continuous-variable nonclassicality
- Experimental violation of the Leggett-Garg inequality under decoherence
- Leggett-Garg test of superconducting qubit addressing the clumsiness loophole
- A macro-realism inequality for opto-electro-mechanical systems
- Experimental violation of the Leggett-Garg inequality in a 3-level system
- Comparing Conditions for Macrorealism: Leggett-Garg Inequalities vs No-Signaling in Time
- The Leggett-Garg inequality in electron interferometers
- Modeling Leggett-Garg-inequality violation
- Leggett-Garg tests for macrorealism: interference experiments and the simple harmonic oscillator
- Violations of a Leggett-Garg inequality without signalling for a photonic qutrit probed with ambiguous measurements
- Leggett-Garg tests of macro-realism for dynamical cat-states evolving in a nonlinear medium
- Necessary and sufficient conditions for macrorealism using two and three-time Leggett-Garg inequalities
- Leggett-Garg inequalities for the statistics of electron transport
- Influence of equilibrium and nonequilibrium environments on macroscopic realism through the Leggett-Garg inequalities
- Violation of Leggett-Garg type inequalities in a driven two level atom interacting with a squeezed thermal reservoir
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