Macroscopic delayed-choice and retrocausality: quantum eraser, Leggett-Garg and dimension witness tests with cat states

Abstract

We propose delayed choice experiments carried out with macroscopic qubits, realised as macroscopically-distinct coherent states $|\alpha ⟩$ and $|-\alpha ⟩$. Quantum superpositions of $|\alpha ⟩$ and $|-\alpha ⟩$ are created via a unitary interaction $U(\theta )$ based on a nonlinear Hamiltonian. Macroscopic delayed-choice experiments give a compelling reason to develop interpretations not allowing macroscopic retrocausality (MrC). We therefore consider weak macroscopic realism (wMR), which specifies a hidden variable ${\lambda }_{\theta }$ to determine the macroscopic qubit value (analogous to 'which-way' information), independent of any future measurement setting $\varphi$. Using entangled states, we demonstrate a quantum eraser where the choice to measure a which-way or wave-type property is delayed. Consistency with wMR is possible, if we interpret the macroscopic qubit value to be determined by ${\lambda }_{\theta }$ without specification of the state at the level of $\hslash$, where fringes manifest. We then demonstrate violations of a delayed-choice Leggett-Garg inequality, and of the dimension witness inequality applied to the Wheeler-Chaves-Lemos-Pienaar experiment, where measurements need only distinguish the macroscopic qubit states. This negates all two-dimensional non-retrocausal models, thereby suggesting MrC. However, one can interpret consistently with wMR, thus avoiding MrC, by noting extra dimensions, and by noting that the violations require further unitary dynamics $U$ for each system. The violations are then explained as failure of deterministic macroscopic realism (dMR), which specifies validity of ${\lambda }_{\theta }$ prior to the dynamics $U(\theta )$ determining the measurement setting $\theta$. Finally, although there is consistency with wMR for macroscopic observations, we demonstrate EPR paradoxes at a microscopic level.

References in corpus (67)

• Bell nonlocality
• Steering, Entanglement, Nonlocality, and the EPR Paradox
• Collapse and Revival of the Matter Wave Field of a Bose-Einstein Condensate
• Quantum Optical Metrology -- The Lowdown on High-N00N States
• The Einstein-Podolsky-Rosen paradox: from concepts to applications
• Experimental criteria for steering and the Einstein-Podolsky-Rosen paradox
• Quantum Steering
• Experimental realization of Wheeler's delayed-choice GedankenExperiment
• Observation of quantum state collapse and revival due to the single-photon Kerr effect
• A Delayed Choice Quantum Eraser
• Entanglement, EPR-correlations, Bell-nonlocality, and Steering
• Leggett-Garg Inequalities
• Experimental violation of a Bell's inequality in time with weak measurement
• A Schrodinger Cat Living in Two Boxes
• A double-slit quantum eraser
• Testing the Hilbert space dimension
• Device-independent tests of classical and quantum dimensions
• Violation of the Leggett-Garg inequality with weak measurements of photons
• A quantum delayed choice experiment
• Soundness and completeness of quantum root-mean-square errors
• Weak values and the Leggett-Garg inequality in solid-state qubits
• Unconditional violation of the shot noise limit in photonic quantum metrology
• Delayed-choice gedanken experiments and their realizations
• Macroscopic quantum states: measures, fragility and implementations
• Entanglement-enabled delayed choice experiment
• Experimental Violation of Two-Party Leggett-Garg Inequalities with Semi-weak Measurements
• Proposal for a quantum delayed-choice experiment
• A strict experimental test of macroscopic realism in a superconducting flux qubit
• Experimental Device-independent Tests of Classical and Quantum Dimensions
• Certifying the dimension of classical and quantum systems in a prepare-and-measure scenario with independent devices
• Quantum erasure with causally disconnected choice
• Generic Bell inequalities for multipartite arbitrary dimensional systems
• Leggett-Garg inequality with a kicked quantum pump
• Deterministic protocol for mapping a qubit to coherent state superpositions in a cavity
• Entanglement of photons in their dual wave-particle nature
• Necessary and sufficient conditions for macroscopic realism from quantum mechanics
• Probing macroscopic realism via Ramsey correlations measurements
• Failure of Local Realism Revealed by Extremely Coarse-Grained Measurements
• Coarsening Measurement References and the Quantum-to-Classical Transition
• Decoherence of Einstein-Podolsky-Rosen steering
• A measure of physical reality
• Experimental test of non-macrorealistic cat-states in the cloud
• Causal modeling the delayed choice experiment
• Quantum non-demolition measurement enables macroscopic Leggett-Garg tests
• Multiparty multilevel Greenberger-Horne-Zeilinger states
• Leggett-Garg macrorealism and the quantum nondisturbance conditions
• Spin entanglement, decoherence and Bohm's EPR paradox
• Is wave-particle objectivity compatible with determinism and locality?
• Quantum delayed-choice experiment with a beam splitter in a quantum superposition
• Quantifying the mesoscopic quantum coherence of approximate NOON states and spin-squeezed two-mode Bose-Einstein condensates
• Interference experiment, anomalous weak value and Leggett-Garg test of macrorealism
• Avoiding Loopholes with Hybrid Bell-Leggett-Garg Inequalities
• Device independent certification of a quantum delayed choice experiment
• Leggett-Garg tests for macrorealism: interference experiments and the simple harmonic oscillator
• Realization of a causal-modeled delayed-choice experiment using single photons
• Irrealism from fringe visibility in matter-wave double-slit interference with initial contractive states
• Signifying the nonlocality of NOON states using Einstein-Podolsky-Rosen steering inequalities
• A loophole-free Wheeler-delayed-choice experiment
• Leggett-Garg tests of macro-realism for multi-particle systems including double-well Bose-Einstein condensates
• The 'Delayed Choice Quantum Eraser' Neither Erases Nor Delays
• Testing macroscopic local realism using cat-states and Bell inequalities in time
• Leggett-Garg tests of macro-realism for dynamical cat-states evolving in a nonlinear medium
• Classical model of delayed-choice quantum eraser
• Restrictions for the Causal Inferences in an Interferometric System
• Conditions for Macrorealism for Systems Described by Many-Valued Variables
• Modified quantum delayed-choice experiment without quantum control
• Alternative analysis of the delayed-choice quantum eraser with two entangled particles

Cited by in corpus (7)

• Mesoscopic and macroscopic quantum correlations in photonic, atomic and optomechanical systems
• Weak versus deterministic macroscopic realism, and Einstein-Podolsky-Rosen's elements of reality
• A macroscopic quantum three-box paradox: finding consistency with weak macroscopic realism
• Quantum observable's reality erasure with spacelike-separated operations
• Violation of Diagonal Non-Invasiveness: A Hallmark of Non-Classical Memory Effects
• Correlating Local Quantum Reality with Causally Disconnected Choices
• Forward-backward stochastic simulations: Q-based model for measurement and Bell-nonlocality consistent with weak local realistic premises