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Clocks without “Time” in Entangled-State Experiments

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Harvard School of Engineering and Applied Sciences, Cambridge, MA 02138, USA
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Entropy 2020, 22(4), 434;
Received: 15 February 2020 / Revised: 30 March 2020 / Accepted: 8 April 2020 / Published: 11 April 2020
(This article belongs to the Collection Locality and Non-Locality, and Their Relation to Time)
Entangled states of light exhibit measurable correlations between light detections at separated locations. These correlations are exploited in entangled-state quantum key distribution. To do so involves setting up and maintaining a rhythm of communication among clocks at separated locations. Here, we try to disentangle our thinking about clocks as used in actual experiments from theories of time, such as special relativity or general relativity, which already differ between each other. Special relativity intertwines the concept of time with a particular definition of the synchronization of clocks, which precludes synchronizing every clock to every other clock. General relativity imposes additional barriers to synchronization, barriers that invite seeking an alternative depending on any global concept of time. To this end, we focus on how clocks are actually used in some experimental situations. We show how working with clocks without worrying about time makes it possible to generalize some designs for quantum key distribution and also clarifies the need for alternatives to the special-relativistic definition of synchronization. View Full-Text
Keywords: entangled light states; synchronization; agent; unpredictability entangled light states; synchronization; agent; unpredictability
MDPI and ACS Style

Madjid, F.H.; Myers, J.M. Clocks without “Time” in Entangled-State Experiments. Entropy 2020, 22, 434.

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