Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Macroscopic delayed-choice and retrocausality: quantum eraser,
  Leggett-Garg and dimension witness tests with cat states   We propose delayed choice experiments carried out with macroscopic qubits,
realised as macroscopically-distinct coherent states $|\alpha\rangle$ and
$|-\alpha\rangle$. Quantum superpositions of $|\alpha\rangle$ and
$|-\alpha\rangle$ 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 $\phi$. 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 $\hbar$, 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.

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The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: atom-ph
3
The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-th