Asking Photons Where They Have Been

Abstract

We present surprising experimental evidence regarding the past of photons passing through an interferometer. The information about the positions through which the photons pass in the interferometer is retrieved from modulations of the detected signal at the vibration frequencies of mirrors the photons bounce off. From the analysis we conclude that the past of the photons is not represented by continuous trajectories, although a "common sense" analysis adopted in various welcher weg measurements, delayed-choice which-path experiments, and counterfactual communication demonstrations yields a single trajectory. The experimental results have a simple explanation in the framework of the two-state vector formalism of quantum theory.

Can the two-time interpretation of quantum mechanics solve the measurement problem?

“…Here I am grateful to Emily Adlam. 19 That is: determinism is restored in the two-time, and so 'looking ahead', sense discussed in section 3.1.3.…”

“…Can we, or should, we assign a trajectory? In this connection, Vaidman suggests that the TSVF is illuminating: in particular, it is the right formalism for describing the past of a quantum particle [40,19].…”

“…18 The generic twostate vector fails to determine all measurement outcomes and so the final state Φ| DES is needed to restore determinism. 19 However, this move undermines the treatment of Φ| and |Ψ in the two-time 3), it is not necessary to think that Φ| causes it. Whilst it is consistent to think of Φ| as determining the outcome in these special cases, one could equally hold that the intermediate measurement changes |Ψ to |Ψ which then determines that postselection outcome (and thus defines Φ|).…”

Honoring Epimenides of Crete (±Δx): From Quantum Paradoxes, through Weak Measurements, to the Nature of Time

“…A recent experiment of joint weak and interaction free measurement is suggested in [30,31]. Weak measurements validating the Hardy paradox (Sec.…”

Beyond the operator algebra—To be nonlocal realism of quantum mechanics

“…the determinists argued that the past of photons should be realistic and deterministic prior to the detection. Despite the results obtained 5 years ago in various delayed-choice experiments seem to have rejected the realistic interpretation, the recently observed wave-particle superposition and disconnected propagation history make the long-standing debate more intense [6,7]. Owing to the recent advance in science of structured light [8,9], the new finding of the subluminal feature of twisted light enables us to see the real past of photons after being registered; consequently, the nonlocal reality of the quantum world was finally confirmed in 2017 [10,11].…”