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arXiv:2208.05792

Anti-Correlated Photons from Classical Electromagnetism

K. B. Wharton, Emily Adlam

Published Aug 11, 2022• 0 citations
arXivHTMLPDF

Abstract

For any experiment with two entangled photons, some joint measurement outcomes can have zero probability for a precise choice of basis. These perfect anti-correlations would seem to be a purely quantum phenomenon. It is therefore surprising that these very anti-correlations are also evident when the input to the same experiment is analyzed via classical electromagnetic theory. Demonstrating this quantum-classical connection for arbitrary two-photon states (and analyzing why it is successful) motivates alternative perspectives concerning entanglement, the path integral, and other topics in quantum foundations.

DOI
10.48550/arxiv.2208.05792

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V18 Future B Event: Conditional Correlation vs No-SignallingTests whether later B measurement outcomes correlate with the earlier Path while checking whether the unconditional earlier Path marginal remains unchanged. Version 19 — Explicit Causal Ordering:Introduced density-matrix tracking, trace-distance, and mutual-information tests. Results confirmed zero accessible information about future random measurement choices in earlier path records, supporting no-signalling and causal ordering within the computational model. Version 20 — Unified Quantum–Temporal Computational Model:Integrated Bell-state entanglement, controlled photon diversion, and path-dependent temporal wavepackets with effective positive/negative temporal shifts. The framework enables both future-conditioned correlations and non-selective analysis, while preserving the no-signalling constraint. Version 21 — Causality & No-Signalling Test This version computationally tests causal influence in the Quantum Feed-Forward Diverter Loop using entanglement, controlled photon diversion, temporal wavepackets, and effective negative time shifts. The results distinguish quantum correlation from controllable retrocausal signalling. The negative temporal shift remains a mathematical model, not literal backward time propagation. No physical retrocausality or violation of the No-Signalling Theorem is demonstrated. Version 22 Figure 1 — Path-dependent Temporal Wavepackets Shows two path-dependent temporal wavepackets with different effective temporal shifts. Path-0 is centered at zero, while Path-1 is shifted to an earlier effective time coordinate. 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•Aug 24, 2026•0 citations
For any experiment with two entangled photons, some joint measurement outcomes can have zero probability for a precise choice of basis. These perfect anti-correlations would seem to be a purely quantum phenomenon. It is therefore surprising that these very anti-correlations are also evident when the input to the same experiment is analyzed via classical electromagnetic theory. Demonstrating this quantum-classical connection for arbitrary two-photon states (and analyzing why it is successful) motivates alternative perspectives concerning entanglement, the path integral, and other topics in quantum foundations.
For any experiment with two entangled photons, some joint measurement outcomes can have zero probability for a precise choice of basis. These perfect anti-correlations would seem to be a purely quantum phenomenon. It is, therefore, surprising that these very anti-correlations are also evident when the input to the same experiment is analyzed via classical electromagnetic theory. Demonstrating this quantum–classical connection for arbitrary two-photon states and analyzing why it is successful motivates alternative perspectives concerning entanglement, the path integral, and other topics in quantum foundations.
We wish to report an experimental observation of anti-correlation from first-order incoherent classical chaotic light. We explain why the classical statistical theory does not apply and provide a quantum interpretation. In quantum theory, either correlation or anti-correlation is a two-photon interference phenomenon, which involves the superposition of two-photon amplitudes, a nonclassical entity corresponding to different yet indistinguishable alternative ways of producing a joint-photodetection event.
The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell's theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell's theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single- and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein's contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that nature cannot be local, that objective randomness exists and about the emergence of a classical world. It is suggestive that information plays a fundamental role also in the foundations of quantum physics.
At what level of energy does a classical experiment become quantum mechanical? Where does classical electromagnetic theory apply and where do we have to turn to quantum optics? Is there a sharp line between these two models? And if so: why, and why at this level? Or if not: what are the common features of the formalisms, and what are the di erences? With our upcoming experimental work, we hope to be able to gain some insight into these challenging questions. The starting point is an investigation of the results from an ordinary Bell type experiment showing entanglement between two photons, where the photons has been generated using spontaneous parametric down conversion, and the same experiment but with a classical source where two highly attenuated pulses are combined. Here we will present in detail our planned experiment.
This scientific proposal outlines a unique thought experiment combining ultra-cold Rubidium atomic clouds in a negative time dwell state with quantum entanglement triggers. The framework utilizes a quantum feed-forward mechanism to route incoming photon light pulses onto an alternate path, effectively presenting a theoretical layout to bypass temporal grandfather paradoxes without inducing a system-wide wavefunction collapse. "Update (Version 2): Added Python (Qiskit) simulation script to verify quantum state routing logic." Implemented a 4-Case Marginal Probability Matrix simulation (Z-basis, X-basis, No-measurement, and Random-basis) to rigorously verify that the system strictly obeys the No-Signaling Theorem and preserves causality under feed-forward routing conditions. Update (Version 4): Integrated an advanced Time-Symmetric / Post-Selected Diverter Test framework. Successfully verified a 100% quantum state correlation conditioned on future measurement outcomes while strictly preserving the global No-Signaling theorem constraint. Version 5 Update — Temporal Wavepacket and Effective Negative Group-Delay Model This version extends the Quantum Feed-Forward Diverter Loop thought experiment by introducing a temporal wavepacket model for the photon and an effective frequency-domain transfer function representing positive and negative group delays. The photon is modeled as a Gaussian temporal wavepacket. Two alternative pathways are assigned effective delays, with Path-1 represented by a positive delay and Path-2 by an effective negative group delay. The resulting temporal wavepackets are numerically propagated and compared to visualize the corresponding temporal shifts. The quantum-routing component is then combined with an entangled A–B pair, photon–B interaction, and A-controlled quantum path diversion. The simulation evaluates both the unconditional photon-path distribution and the post-selected correlation between the earlier photon path and the later B measurement outcome. Using 20,000 simulated shots, the unconditional path probabilities were approximately: P(Path=0) = 0.5000P(Path=1) = 0.5000 Post-selection produced perfect conditional correlations in this circuit model: P(Path=0 | B=0) = 1.0000P(Path=1 | B=1) = 1.0000 These results demonstrate temporal-wavepacket shifting and strong conditional quantum correlation within the computational model. The effective negative group delay is used as a mathematical transfer-function parameter and is not interpreted as literal backward propagation of a photon or proof of retrocausality. This version is intended as a theoretical/computational extension of the proposed Quantum Feed-Forward Diverter Loop and does not constitute an experimental demonstration of negative time, retrocausal signalling, or violation of the quantum no-signalling principle. Version 6 Update — Coupled Temporal–Quantum Counterfactual Test This version extends the Quantum Feed-Forward Diverter Loop by coupling the temporal wavepacket framework with the quantum A–B diverter model and introducing an explicit future-measurement-choice test. The photon is represented as a temporal wavepacket, while the two quantum paths are associated with different effective transfer functions. Path-1 is assigned an effective negative group delay. The quantum model includes A–B entanglement, photon–B interaction, and A-controlled path diversion. The model tests whether changing the future measurement basis of particle B can alter the earlier photon-path marginal distribution without classical communication. Four future measurement conditions were compared: Z basis, X basis, Random basis, and No measurement. Using 20,000 simulated shots, the earlier-path probabilities were approximately: P(Earlier Path=0): Z basis = 0.4992 X basis = 0.4979 Random basis = 0.4979 No measurement = 0.5013 P(Earlier Path=1): Z basis = 0.5008 X basis = 0.5021 Random basis = 0.5021 No measurement = 0.4986 The results show that the earlier photon-path marginal remains approximately 50:50 across the different future measurement choices. No controllable change in the earlier marginal distribution was observed in this computational model. Conditional correlations between the photon path and the later B outcome remain present, demonstrating the distinction between quantum correlation and usable retrocausal signalling. This version therefore provides a counterfactual/no-signalling test of the proposed mechanism. It does not demonstrate literal backward time, retrocausal communication, or a violation of the quantum no-signalling principle. Important: The negative group delay remains an effective temporal transfer-function parameter and should not be interpreted as literal backward propagation of the photon. Version 7 A coupled computational model combining temporal wavepacket shifts with quantum path control and future-conditioned A–B correlations was implemented. The earlier-path marginal remained approximately 50:50 in the tested configuration, while perfect conditional Path–B correlations were observed. Version 8 Update — Future-Choice / Retrocausal Marginal Test This version extends the Quantum Feed-Forward Diverter Loop computational model by testing whether an independently selected future measurement basis of qubit B can statistically alter the earlier photon-path marginal distribution. The model retains the joint temporal-wavepacket and quantum-path framework introduced in Version 7, including: Path-0 coupled to a positive-delay temporal wavepacket. Path-1 coupled to an effective negative-delay temporal wavepacket. Quantum A–B correlations and photon–B interaction. Earlier photon-path measurement performed before the future B measurement. Independent variation of the future B measurement choice. Four future-choice conditions were compared: Z basis, X basis, no measurement, and random basis. For the principal Z-versus-X comparison, the simulated results were: P(Path=0 | future B=Z) = 0.498150 P(Path=0 | future B=X) = 0.499450 Difference = −0.001300 Z-score = −0.260001 Two-sided p-value = 0.794863 No statistically significant difference was detected between the earlier-path marginal distributions under the tested future measurement choices. The simulation therefore provides no evidence of controllable retrocausal signalling within this computational model. Conditional correlations between the earlier path and later B outcomes may still occur, but these correlations do not by themselves demonstrate that a future measurement choice can be used to control an earlier observable. Important limitation: the negative delay used in this model represents an effective mathematical temporal-transfer-function shift. It does not represent literal backward propagation of a photon in time. This Version 8 should therefore be interpreted as a computational test of the no-signalling/retrocausal hypothesis, not as an experimental demonstration of backward time propagation or retrocausal communication. Version 9 - Robustness Test Version 10- Coupled mathematical model Version 11 Coupled Temporal Path Quantum Model & Projective Future Measurement Test Version 13- Mathematical Model Showing no-signalling invariance under the tested future measurement channels Version 14/15 Computetionl test of the proposed retrocausal/causal hypothesis no controllable retrocausal signalling detected V16 Full Feed-Forward Mechanism PrototypeComputational prototype of the proposed B → A → Diverter → Photon Path mechanism, including path-dependent positive/negative effective temporal shifts and correlation analysis. V17 Quantum B–A–Diverter–Photon Path ModelBell-state quantum model connecting A–B entanglement, A-controlled photon diversion, Path correlations, and future B measurement, with a no-signalling test. V18 Future B Event: Conditional Correlation vs No-SignallingTests whether later B measurement outcomes correlate with the earlier Path while checking whether the unconditional earlier Path marginal remains unchanged. Version 19 — Explicit Causal Ordering:Introduced density-matrix tracking, trace-distance, and mutual-information tests. Results confirmed zero accessible information about future random measurement choices in earlier path records, supporting no-signalling and causal ordering within the computational model. Version 20 — Unified Quantum–Temporal Computational Model:Integrated Bell-state entanglement, controlled photon diversion, and path-dependent temporal wavepackets with effective positive/negative temporal shifts. The framework enables both future-conditioned correlations and non-selective analysis, while preserving the no-signalling constraint. Version 21 — Causality & No-Signalling Test This version computationally tests causal influence in the Quantum Feed-Forward Diverter Loop using entanglement, controlled photon diversion, temporal wavepackets, and effective negative time shifts. The results distinguish quantum correlation from controllable retrocausal signalling. The negative temporal shift remains a mathematical model, not literal backward time propagation. No physical retrocausality or violation of the No-Signalling Theorem is demonstrated. Version 22 Figure 1 — Path-dependent Temporal Wavepackets Shows two path-dependent temporal wavepackets with different effective temporal shifts. Path-0 is centered at zero, while Path-1 is shifted to an earlier effective time coordinate. Figure 2 — Conditional vs Non-selective Temporal Distribution Compares the temporal distributions conditioned on B=0/Path-0 and B=1/Path-1 with their non-selective average, illustrating conditional temporal correlations without implying physical backward-time propagation. Version 23 presents a computational no-signaling and causality test for the Quantum Feed-Forward Diverter Loop. The model compares unconditional B statistics and non-selective temporal distributions under