Testing macroscopic local realism using local nonlinear dynamics and time settings

Thenabadu, Manushan; Cheng, Guangling; Pham, T.; Drummond, L. V.; Rosales-Zárate, L.; Reid, M. D.

doi:10.1103/physreva.102.022202

Cited by 19 publications

(45 citation statements)

References 97 publications

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“…There is thus a consistency with macroscopic realism, without any need to introduce decoherence. The apparently contradictory claims in the literature of violations of macroscopic Bell inequalities [39] and Leggett-Garg's macro-realism [40,41] can be explained, once one accounts for the dynamical nature of the measurement process [42]. This does not imply that the system in the superposition was actually in one or the other eigenstate |x 1 or |x 2 (or indeed in any quantum state), prior to measurement.…”

Section: Objective Fieldsmentioning

confidence: 99%

Objective Quantum Fields, Retrocausality and Ontology

Drummond

Reid

2021

Entropy

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We compare different approaches to quantum ontology. In particular, we discuss an interpretation of quantum mechanics that we call objective quantum field theory (OQFT), which involves retrocausal fields. Here, objective implies the existence of fields independent of an observer, but not that the results of conjugate measurements are predetermined: the theory is contextual. The ideas and analyses of Einstein and Bohr through to more recent approaches to objective realism are discussed. We briefly describe measurement induced projections, the guided wave interpretation, many-universes, consistent histories and modal theories. These earlier interpretations are compared with OQFT. We argue that this approach is compatible both with Bohr’s quantum complementarity and Einstein’s objective realism.

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Section: Objective Fieldsmentioning

confidence: 99%

Objective Quantum Fields, Retrocausality and Ontology

Drummond

Reid

2021

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“…The dynamics of the unitary evolution ( 5) is well known [29,38,39]. If the system A is prepared in a coherent state |α , then after at time t a = t 3 = π/2Ω, the state of the system A is [30][31][32]…”

Section: A Set-upmentioning

confidence: 99%

“…Specifically, we follow [30][31][32] and map from a microscopic to a macroscopic regime, where spin qubits | ↑ and | ↓ are realised as macroscopically distinct coherent states |α and | − α (α is large), that form a macroscopic qubit. The qubit values η of +1 and −1 corresponding to the coherent states |α and | − α can be distinguished by a measurement of the field quadrature amplitude X, without the need to resolve at the level of .…”

Section: Introductionmentioning

confidence: 99%

“…The qubit values η of +1 and −1 corresponding to the coherent states |α and | − α can be distinguished by a measurement of the field quadrature amplitude X, without the need to resolve at the level of . In analogy with a polarising beam splitter (PBS) used in the photonic experiments, superpositions of the two coherent states (called cat states) [29][30][31][32] cos θ|α + i sin θ| − α…”

Section: Introductionmentioning

confidence: 99%

“…However, recent work establishes the need to also carefully consider whether the unitary rotation U (θ) associated with the measurement setting θ has been performed (or not) prior to t M . This leads to two definitions of macroscopic realism, one of which (deterministic macroscopic realism) can be falsified [31,32]. Deterministic macroscopic realism (dMR) asserts a predetermination of outcomes, at a time t, for multiple future choices of θ (e.g.…”

Section: Introductionmentioning

confidence: 99%

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

Thenabadu,

Reid

2021

Preprint

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We propose delayed choice experiments carried out with macroscopic qubits, realised as macroscopically-distinct coherent states |α and | − α . Quantum superpositions of |α and | − α are created via a unitary interaction U (θ) based on a nonlinear Hamiltonian, in analogy with polarising beam splitters used in photonic experiments. 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 λ θ to determine the macroscopic qubit value (analogous to 'which-way' information), independent of any future measurement setting φ. Using entangled cat 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 λ θ without specification of the state at the level of order , 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 conclusions of 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 λ θ prior to the dynamics U (θ) determining the measurement setting θ. Finally, although there is consistency with wMR for macroscopic observations, we demonstrate Einstein-Podolsky-Rosen-type paradoxes at a microscopic level, based on fringe distributions.

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