Entanglement swapping between photons that never coexist in laboratory time provides a clean test of the temporal ordering of quantum measurements without invoking retrocausal signaling. We review the 2013 Physical Review Letters experiment by Megidish et al., correcting several common secondary-source simplifications: the temporal separation was implemented with a 31.6 m free-space delay line (105 ns), the final state of photons 1 and 4 was characterized by quantum-state tomography, and the reported result was a conditional entangled state with approximately 77% fidelity to the target Bell state rather than a standalone Bell-inequality test. We then integrate this experimental basis with a DQ-12 interpretation in which photonic excitations are modeled phenomenologically as phase modes of a higher-dimensional continuous state substrate. Within that interpretation, detection is treated as a local relaxation map, while the Bell-state projection on the intermediate photons is represented as a conditional phasebridging operation. Crucially, the standard quantum-mechanical account is sufficient for the observed experiment; DQ-12 is therefore presented not as a confirmed explanation but as an additional ontology that acquires scientific content only through differential, falsifiable predictions. We propose residual observables, delay-dependent tests, matched controls, and a null hypothesis that reduce the DQ-12 claim to an experimentally decidable extension.Keywords: entanglement swapping; temporal entanglement; Bell-state measurement; quantum-state tomography; timelike separation; DQ-12; phase connectivity; emergent time; quantum foundations.
Entanglement swapping between photons that never coexist in laboratory time provides a clean test of the temporal ordering of quantum measurements without invoking retrocausal signaling. We review the 2013 Physical Review Letters experiment by Megidish et al., correcting several common secondary-source simplifications: the temporal separation was implemented with a 31.6 m free-space delay line (105 ns), the final state of photons 1 and 4 was characterized by quantum-state tomography, and the reported result was a conditional entangled state with approximately 77% fidelity to the target Bell state rather than a standalone Bell-inequality test. We then integrate this experimental basis with a DQ-12 interpretation in which photonic excitations are modeled phenomenologically as phase modes of a higher-dimensional continuous state substrate. Within that interpretation, detection is treated as a local relaxation map, while the Bell-state projection on the intermediate photons is represented as a conditional phasebridging operation. Crucially, the standard quantum-mechanical account is sufficient for the observed experiment; DQ-12 is therefore presented not as a confirmed explanation but as an additional ontology that acquires scientific content only through differential, falsifiable predictions. We propose residual observables, delay-dependent tests, matched controls, and a null hypothesis that reduce the DQ-12 claim to an experimentally decidable extension.Keywords: entanglement swapping; temporal entanglement; Bell-state measurement; quantum-state tomography; timelike separation; DQ-12; phase connectivity; emergent time; quantum foundations.
The role of the timing and order of quantum measurements is not just a fundamental question of quantum mechanics, but also a puzzling one. Any part of a quantum system that has finished evolving can be measured immediately or saved for later, without affecting the final results, regardless of the continued evolution of the rest of the system. In addition, the nonlocality of quantum mechanics, as manifested by entanglement, does not apply only to particles with spacelike separation, but also to particles with timelike separation. In order to demonstrate these principles, we generated and fully characterized an entangled pair of photons that have never coexisted. Using entanglement swapping between two temporally separated photon pairs, we entangle one photon from the first pair with another photon from the second pair. The first photon was detected even before the other was created. The observed two-photon state demonstrates that entanglement can be shared between timelike separated quantum systems.
A 2015 experiment by Hanson and Delft colleagues provided new confirmation that the quantum world violates the Bell inequalities, being the first Bell test to close two known experimental loopholes simultaneously. The experiment was also taken to provide new evidence of quantum nonlocality. Here we argue for caution about the latter claim. The Delft experiment relies on entanglement swapping, and our main claim is that this geometry introduces new loopholes in the argument from violation of the Bell inequalities to nonlocality. In the absence of retrocausality, the sensitivity of such experiments to these new loopholes depends on the temporal relation between the entanglement swapping measurement C and the two measurements A and B between which we seek to infer nonlocality. The loopholes loom large if the C is in the future of A and B, but not if C is in the past. The Delft experiment itself is the intermediate case, in which the separation is spacelike. We argue that this leaves it vulnerable to the new loopholes, unable to establish conclusively that it avoids them. We also discuss the implications of permitting retrocausality for the issue of causal influence across entanglement swapping measurements.
This article develops an expanded critical-propositional analysis of Xiao-song Ma, Stefan Zotter, Johannes Kofler, Rupert Ursin, Thomas Jennewein, Časlav Brukner, and Anton Zeilinger’s 2012 experiment, “Experimental Delayed-Choice Entanglement Swapping,” published in Nature Physics 8: 479–484, DOI 10.1038/nphys2294, in systematic dialogue with the Theory of Objectivity (TO) formulated by Vidamor Cabannas and Denivaldo Silva. Ma et al. experimentally realized Asher Peres’s delayed-choice entanglement- swapping proposal by producing two entangled photon pairs and temporally delaying a randomly selected measurement on two of the photons until after the other two photons had already been detected. Victor’s later measurement could be configured either as a Bell-state measurement or as a separable-state measurement. Conditional sorting of the earlier records of Alice and Bob then yielded subensembles exhibiting either quantum entanglement or separable correlations. The experiment employed approximately 7 m optical paths for photons measured by Alice and Bob and approximately 104 m fiber delays for the photons sent to Victor. Victor’s measurement occurred about 485 ns after Alice’s and Bob’s detections, while his choice occurred between approximately 14 and 313 ns after those detections. The Bell-state configuration produced a reported fidelity of FBSM = 0.681 ± 0.034 and an entanglement-witness value of WBSM = −0.181 ± 0.034, whereas the separable-state configuration yielded a fidelity of FSSM = 0.421 ± 0.029 and a witness value of WSSM = 0.078 ± 0.029 (Ma et al. 2012). The article examines these results in relation to the Seven Absolute Truths of TO, with particular emphasis on the Fifth Absolute Truth, according to which an element requires relational observation or inclusion within the frequency of at least two other elements in order to possess logical existence. In TO, observation is not reducible to human consciousness; it is an objective relation among physical elements. The Ma experiment does not prove this universal modal proposition, but it offers an unusually relevant empirical domain in which physically meaningful classifications are dependent on multipartite relations rather than on isolated local records. The Fourth and Sixth Absolute Truths are likewise examined in relation to physical boundaries, interfaces, composition, and redistribution of entanglement. The Second Absolute Truth generates a productive tension with quantum indistinguishability, because TO attributes to every element its own exclusive field of individuation, whereas quantum optical interference presupposes operational indistinguishability among identical photons. Special attention is given to the TO concept of the transcendent element as knowledge or information generated in atomic relations and equivalent, within TO, to atomic radiation. Ma et al.’s experiment directly establishes an operational nexus among electromagnetic radiation, polarization information, physical correlations, measurement contexts, and recorded data, but it does not independently establish the stronger ontological identity between information and radiation proposed by TO. The article therefore distinguishes empirical consonance, operational compati- bility, ontological interpretation, and modal necessity. It argues that the scientifically strongest relation between Ma et al. and TO lies not in claiming confirmation of the entire theory but in constructing testable operational bridges, especially around relational observation, boundaries, physical information, non-simultaneity, and the dis- tinction between individual and relational properties. A TO-style appendix concludes the paper by formalizing possible operational bridges and research propositions for future empirical investigation. Keywords: Theory of Objectivity; delayed-choice entanglement swapping; quantum entanglement; relational observation; information; photon; Bell-state measurement; modal ontology; non-simultaneity; transcendent element; quantum foundations.
Quantum entanglement is a central resource of quantum information science, yet its correlations are ordinarily treated as properties of the quantum state rather than as the outcome of an underlying physical process. Here we explore the hypothesis that these correlations are mediated dynamically by a field propagating locally at finite velocity through an extension of ordinary spacetime. The model embeds physical (3,1)-dimensional spacetime in a warped five-dimensional geometry containing an additional timelike coordinate. Within the adopted geometric ansatz, the form of the extended spacetime metric is determined by the five-dimensional vacuum Einstein equations. A massless field propagating through the resulting five-dimensional bulk can mediate correlations whose projection onto observable four-dimensional spacetime connects arbitrarily distant locations at equal laboratory time, while preserving operational no-signaling. Coupling this field to a Bohm--Bub-inspired collapse scheme provides a possible dynamical realization of entanglement correlations and, under a stated statistical consistency condition, reproduces Born statistics. The framework leads to a concrete experimental test. Two nominally independent Bell pairs are predicted to develop a weak, distance-dependent contextual correlation between particles belonging to different pairs, as a consequence of bulk-field mediation. This cross-pair correlation is absent in standard quantum mechanics for independently prepared systems and is predicted to decrease as the inverse square of their separation. It could therefore be tested by varying the distance between two simultaneous Bell experiments using existing photonic technology. Observation of such a signal would support a dynamical spacetime account of quantum entanglement and could have implications for quantum networks employing multiple independent entangled resources.
John Bell’s theorem of 1964 states that local elements of physical reality, existing independent of measurement, are inconsistent with the predictions of quantum mechanics (Bell, J. S. (1964), Physics (College. Park. Md). Specifically, correlations between measurement results from distant entangled systems would be smaller than predicted by quantum physics. This is expressed in Bell’s inequalities. Employing modifications of Bell’s inequalities, many experiments have been performed that convincingly support the quantum predictions. Yet, all experiments rely on assumptions, which provide loopholes for a local realist explanation of the measurement. Here we report an experiment with polarization-entangled photons that simultaneously closes the most significant of these loopholes. We use a highly efficient source of entangled photons, distributed these over a distance of 58.5 meters, and implemented rapid random setting generation and high-efficiency detection to observe a violation of a Bell inequality with high statistical significance. The merely statistical probability of our results to occur under local realism is less than 3.74×10-31, corresponding to an 11.5 standard deviation effect.
We experimentally entangle freely propagating particles that never physically interacted with one another or which have never been dynamically coupled by any other means. This demonstrates that quantum entanglement requires the entangled particles neither to come from a common source nor to have interacted in the past. In our experiment we take two pairs of polarization entangled photons and subject one photon from each pair to a Bell-state measurement. This results in projecting the other two outgoing photons into an entangled state.