Past of a particle in an entangled state

Abstract

Vaidman has proposed a controversial criterion for determining the past of a single quantum particle based on the "weak trace" it leaves. We here consider more general examples of entangled systems and analyze the past of single, as well as pairs of entangled pre- and postselected particles. Systems with non-trivial time evolution are also analyzed. We argue that in these cases, examining only the single-particle weak trace provides information which is insufficient for understanding the system as a whole. We therefore suggest to examine, alongside with the past of single particles, also the past of pairs, triplets and eventually the entire system, including higher-order, multipartite traces in the analysis. This resonates with a recently proposed top-down approach by Aharonov, Cohen and Tollaksen for understanding the structure of correlations in pre- and postselected systems.

arXiv commentAdded one reference and corrected a typo. Accepted to Int. J. Quantum Inf

References in corpus (15)

• Revisiting Hardy's Paradox: Counterfactual Statements, Real Measurements, Entanglement and Weak Values
• The past of a quantum particle
• Extracting joint weak values with local, single-particle measurements
• Measuring incompatible observables of a single photon
• Broadening the scope of weak quantum measurements I: A single particle accurately measured yet left superposed
• Broadening the scope of weak quantum measurements II: Past and future measurement effects within a double Mach-Zehnder-interferometer setting
• Particle Path Through a Nested Mach-Zehnder Interferometer
• Tracing the past of a quantum particle
• Past of a quantum particle: Common sense prevails
• The Case of the Disappearing (and Re-Appearing) Particle
• Experimental observation of anomalous trajectories of single photons
• Nonlocal Measurements via Quantum Erasure
• A Comment on "Paradox of photons disconnected trajectories being located by means of 'weak measurements' in the nested Mach-Zehnder interferometer"
• Quantum weak values and logic, an uneasy couple
• Quantum to Classical Transitions via Weak Measurements and Post-Selection

Cited by in corpus (8)

• Comment on "Past of a quantum particle revisited"
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• Weak values and the past of a quantum particle
• Reply to Comment on "Null weak values and the past of a quantum particle" by D. Sokolovski
• Comment on "Multifold paths of neutrons in the three-beam interferometer detected by a tiny energy kick"
• Photonic realization of erasure-based nonlocal measurements
• Time-symmetry and topology of the Aharonov-Bohm effect
• Do neutrons disagree with photons about where they have been inside an interferometer?