The interpretations of the delayed-choice experiments suggest that photons i°retroactively decidei± to travel as particles or as waves from the time of its emission. To test the interpretations thoroughly, we propose and perform novel extended-delayed-choice experiments. The experiments are designed for easier to set up, carry out and reach meaningful results without ambiguity. The experimental results show the following: (A) The present does not decide the past retroactively, i.e., the causality holds; (B) Bohri¯s complementarity principle is challenged; (C) photons behave as particle before striking on a double-slit/cross-double-slit; (D) Particle nature is intrinsic.
The interpretations of the delayed-choice experiments suggest that photons i°retroactively decidei± to travel as particles or as waves from the time of its emission. To test the interpretations thoroughly, we propose and perform novel extended-delayed-choice experiments. The experiments are designed for easier to set up, carry out and reach meaningful results without ambiguity. The experimental results show the following: (A) The present does not decide the past retroactively, i.e., the causality holds; (B) Bohri¯s complementarity principle is challenged; (C) photons behave as particle before striking on a double-slit/cross-double-slit; (D) Particle nature is intrinsic.
The interpretations of the delayed-choice experiments suggest that photons "retroactively decide" to travel as particles or as wave from the time of its emission. To test the interpretations thoroughly, we propose and perform extended-delayed-choice experiments. The experiments are designed for easier to set up, carry out and reach meaningful results without ambiguous. The experimental results show the following: (A) the causality holds; (B) Bohr's complementarity principle is violated; (C) photons behave as particle before striking at output beam splitter/double-slit/crossdouble-slit; (D) the present does not determine the past retroactively, but determines the future.
We have performed cross-double-slit experiment and delayed-choice-cross-double-slit experiment, denoted as extended double-slit experiments. The cross-double-slit experiments show that the cross-double-slit apparatus creates not only two interference patterns, but also four cross-interference-patterns, which are created by two double-slit. The delayed-choice-cross-double-slit experiments disclose new phenomena: (1) photons behave as both wave and particle in the same experiment simultaneously, which violate Bohr’s complementarity; (2) the cross-interference-pattern is created by one double-slit and one single-slit; (3) photons passing through the same slit behave as both wave and particle, referred it as the Wave-Particle-Paradox, which demands extensive study. We suggest to re-study wave-particle duality.
Wheeler's delayed-choice experiment appears to show that a choice made now retroactively determines whether a photon behaved as a wave or particle in the past — even billions of years ago in the cosmic version. This has been interpreted as evidence for retrocausality, the role of consciousness in collapsing the wave function, or the many-worlds interpretation. We show that none of these interpretations is required. In the information processing load framework established in Papers 4 and 7, the photon propagates with n ≈ 0 environmental interactions throughout its journey. Since n = 0 < n* for all physical photons, the condition C_wave < C_particle holds: the wave state is maintained for the entire propagation duration, regardless of whether that duration is nanoseconds or 10 Gyr. The experimenter's detector setting determines only n_detector at the moment of detection — not the photon's state during propagation. The interference visibility function is V = max(0, 1 − n_detector/n*): full interference when n_detector = 0, no interference when n_detector ≥ n*. We verify numerically that a photon from a quasar 10 Gly distant accumulates n ≈ 2.6 × 10⁶ CMB scatterings during propagation, while n* ≈ 82 for a 500 nm photon — confirming n << n* and wave state maintenance. The apparent retrocausality is a consequence of a misidentification: the question 'which path did the photon take during propagation?' presupposes a definite path during propagation, but in the load framework the photon was not in a path-definite state. There is no fact of the matter about the path during propagation. The detector choice at detection determines what question can meaningfully be asked — not what happened in the past.Wheeler's delayed-choice experiment appears to show that a choice made now retroactively determines whether a photon behaved as a wave or particle in the past — even billions of years ago in the cosmic version. This has been interpreted as evidence for retrocausality, the role of consciousness in collapsing the wave function, or the many-worlds interpretation. We show that none of these interpretations is required. In the information processing load framework established in Papers 4 and 7, the photon propagates with n ≈ 0 environmental interactions throughout its journey. Since n = 0 < n* for all physical photons, the condition C_wave < C_particle holds: the wave state is maintained for the entire propagation duration, regardless of whether that duration is nanoseconds or 10 Gyr. The experimenter's detector setting determines only n_detector at the moment of detection — not the photon's state during propagation. The interference visibility function is V = max(0, 1 − n_detector/n*): full interference when n_detector = 0, no interference when n_detector ≥ n*. We verify numerically that a photon from a quasar 10 Gly distant accumulates n ≈ 2.6 × 10⁶ CMB scatterings during propagation, while n* ≈ 82 for a 500 nm photon — confirming n << n* and wave state maintenance. The apparent retrocausality is a consequence of a misidentification: the question 'which path did the photon take during propagation?' presupposes a definite path during propagation, but in the load framework the photon was not in a path-definite state. There is no fact of the matter about the path during propagation. The detector choice at detection determines what question can meaningfully be asked — not what happened in the past. Keywords: delayed-choice experiment; Wheeler; retrocausality; information processing load; wave function collapse; quantum eraser; cosmic photon; weak measurement; n < n*; no consciousness required
The delayed-choice experiment has long been regarded as one of the most conceptually intriguing demonstrations in quantum mechanics because the measurement configuration can be selected after a quantum system has already entered the experimental apparatus. This feature has often been interpreted as suggesting that the present measurement determines whether the quantum system behaved as a wave or as a particle in the past, thereby motivating discussions of wave–particle duality and retrocausality. This paper reexamines the delayed-choice experiment from the perspective of the Intrinsic Observability Framework (IOF). Rather than interpreting the experiment as demonstrating that the past is modified or that a quantum system intrinsically possesses either wave-like or particle-like properties prior to measurement, the IOF distinguishes between the pre-measurement domain of Potential Observability (PO) and the operational establishment of Observability through measurement. Within this framework, wave-like and particle-like behaviors are interpreted as observable representations established under different accessibility bases rather than intrinsic properties of the quantum system itself. Measurement grants accessibility, thereby establishing an observable representation according to the selected accessibility basis, within which observable values become operationally defined. Consequently, the delayed choice is understood not as selecting whether the quantum system was previously a wave or a particle, but as selecting the accessibility basis through which observability is established. From this perspective, the traditional wave–particle duality is reinterpreted as the basis dependence of observable representation rather than the coexistence of two fundamentally different physical natures. The delayed-choice experiment therefore illustrates how different accessibility bases lead to different observable representations while remaining fully compatible with the standard mathematical formalism of quantum mechanics.
Young's double slit experiments representing the mystery of quantum mechanics have been descripted by wave theories. To study the mystery, the double slit experiments were extended to the cross-double slit experiments. A description should explain all the double slit and cross-double slit experiments consistently. To test the wave description, the two postulates are proposed, which state that before passing through the double slit and before landing on the detector, photons behave as particles, but not as waves. To test the two postulates, the comprehensive double slit/cross-double slit experiments are proposed and performed. By placing shields and/or blockers near the detector/screen, the comprehensive double slit/cross-double slit experiments show that the fringes are created independently and partially, which discloses the particle nature of photons in the double slit/crossdouble slit experiments and violates the wave descriptions. The comprehensive double slit/cross-double slit experiments provide the comprehensive phenomena for developing theoretical model to study the mystery of double slit, complementarity principle, wave-particle duality, and wave theory of light.
The problem of wave-particle duality is considered within the framework of the algebraic approach. Contrary to the widespread belief, we demonstrate that wave-particle duality can be reconciled with the assumption that there exists some local physical reality determining the results of local measurements. A number of quantum experiments—double-slit electron scattering, Wheeler’s delayed choice experiment, the past of photons passed through the interferometer—are discussed using the concept of locality. A clear physical interpretation of these experiments that does not contradict classical concepts is provided.