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Title: Bell test for temporal order using a mass in superposition
Plain: If a heavy mass is in a superposition of two positions, nearby clocks tick at superposed rates, which can put the order of two events in superposition. A proposed Bell-type test would show this order is not fixed in advance by hidden variables.
Precise: Zych, Costa, Pikovski and Brukner (Nature Communications 2019) proposed a Bell-type inequality for the temporal order of events controlled by a massive body in spatial superposition. Using the weak-field proper-time difference $\Delta \tau \sim G M \Delta x t / (c^{2} d^{2})$, determine the minimal mass, separation and coherence time for a violation, and demonstrate it.
Settled by: Observation of the predicted violation with a source mass in spatial superposition.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: (empty)
Posed since: 2019