Interference phenomena are commonly understood as consequences of path indistinguishability and coherence constrained by the availability of which-path information. While delayed-choice and quantum eraser experiments have demonstrated that interference can be restored or suppressed depending on measurement context, such effects are typically implemented through discrete, externally imposed experimental configurations. In this work, propose a delayed-choice interferometric scheme in which interference visibility is regulated adaptively via predictive estimates of informational accessibility. The proposed architecture introduces an operational measure of predictability derived from ensemble-level intensity statistics, which is used to control downstream interferometric elements after the system has traversed the interferometer. This design preserves the delayed-choice character of the experiment while avoiding any modification of standard quantum mechanical formalism or assumptions of retrocausality. Predictability is treated as an informational control parameter rather than as an intrinsic property of the system’s past evolution. The scheme builds upon established complementarity relations and information-theoretic approaches to coherence and decoherence, extending them toward adaptive, feedback-based control of interference. The proposal is experimentally accessible using classical or semi-classical optical components and does not rely on single-particle detection. By reframing interference as a dynamically regulated informational regime, the work provides a bridge between foundational concepts of quantum measurement and practical architectures for coherence control.
Interference phenomena are commonly understood as consequences of path indistinguishability and coherence constrained by the availability of which-path information. While delayed-choice and quantum eraser experiments have demonstrated that interference can be restored or suppressed depending on measurement context, such effects are typically implemented through discrete, externally imposed experimental configurations. In this work, propose a delayed-choice interferometric scheme in which interference visibility is regulated adaptively via predictive estimates of informational accessibility. The proposed architecture introduces an operational measure of predictability derived from ensemble-level intensity statistics, which is used to control downstream interferometric elements after the system has traversed the interferometer. This design preserves the delayed-choice character of the experiment while avoiding any modification of standard quantum mechanical formalism or assumptions of retrocausality. Predictability is treated as an informational control parameter rather than as an intrinsic property of the system’s past evolution. The scheme builds upon established complementarity relations and information-theoretic approaches to coherence and decoherence, extending them toward adaptive, feedback-based control of interference. The proposal is experimentally accessible using classical or semi-classical optical components and does not rely on single-particle detection. By reframing interference as a dynamically regulated informational regime, the work provides a bridge between foundational concepts of quantum measurement and practical architectures for coherence control.
Abstract The relation between interference visibility and path distinguishability is a core pillar of quantum complementarity and decoherence theory. In standard quantum mechanics, all coherence decay in interferometric systems is attributed exclusively to path information leakage, which establishes a one-to-one relation between environmental distinguishability and fringe visibility. However, a fundamental question remains experimentally untested: whether discrete quantized energy exchange between light and matter can degrade quantum coherence independently of path distinguishability. In this work, we propose a high-precision cavity-QED experiment based on a Mach–Zehnder interferometer to decouple interaction modality from path information. A single trapped Rb atom inside an optical cavity is placed in one interferometer arm, enabling fully switchable light–matter interaction regimes: resonant discrete energy exchange and far-detuned continuous dispersive interaction. To eliminate systematic artifacts, we employ environmental state tomography to rigorously equalize the path distinguishability in both operational regimes. Furthermore, we systematically compensate all linear dynamical differences between resonant and dispersive cavity responses, including group delay, spectral distortion, and temporal mode mismatch. With all standard decoherence and dynamical contributions precisely calibrated, standard quantum mechanics predicts identical interference visibility for resonant and dispersive interactions. In contrast, a physically motivated alternative conjecture suggests that discrete energy exchange can induce intrinsic coherence suppression even at fixed path distinguishability. The two scenarios yield experimentally distinguishable visibility differences. Our scheme utilizes mature single-atom cavity quantum optics techniques without low-temperature superconducting devices, providing a robust and accessible platform to resolve this long-standing open question in quantum interferometry. The complete optical layout, timing sequence, tomography calibration, statistical criteria, and error suppression strategies are presented. This experiment offers a decisive experimental benchmark for the fundamental relationship between light–matter interaction type and quantum coherence.
This work presents a unified, interpretive account of quantum interference and delayed-choice experiments that applies equally to photons and massive particles. Rather than invoking spacetime trajectories, wave–particle duality, retrocausality, or collapse postulates, the paper locates quantum interference in the coherent evolution of internal, pre-geometric degrees of freedom defined over classical spacetime. Within this framework, “which-path” questions are not merely unanswered but fundamentally ill-posed: interference arises from global coherence of an internal field subject to experimental boundary conditions, while spacetime itself remains single-valued and classical at laboratory scales. The approach reproduces all standard quantum-mechanical predictions without modification and is explicitly interpretive rather than predictive. A central result is a unified explanation of why interference occurs across disparate physical systems—photons, electrons, atoms, and molecules—while decoherence manifests through system-dependent physical mechanisms. Photons and massive particles differ in how internal coherence is lost (e.g., electromagnetic absorption versus collisional and thermal interactions), but not in the underlying principle. Delayed-choice experiments are reinterpreted without paradox: changes to the apparatus modify boundary conditions for the internal field rather than retroactively altering particle histories. By removing spacetime paths from the fundamental ontology, the framework offers a consistent, path-free account of interference, decoherence, and localized detection that preserves the empirical success of quantum mechanics while clarifying its conceptual foundations.
Delayed-choice experiments challenge classical intuitions by allowing the configuration of an interferometer to be chosen after a quantum system has already entered it. While these experiments support Bohr’s complementarity principle, the introduction of quantum control reveals that the manifestation of complementarity depends critically on the full physical context — including quantum correlations and the causal order of operations. In this work, we propose and analyze a modified entanglement-assisted delayed-choice experiment that maintains the same final visibility as the standard setup but reverses its causal structure. Here, we go beyond output statistics to examine how wave-particle realism evolves throughout the interferometer. Using a contextual realism quantifier, we show that wave and particle realism can be meaningfully assigned at intermediate stages with a clear connection with the final interferometric visibility. Specifically, our results show that modifying the causal order of operations and information structure, whether through entanglement tuning or post-selection, leads to significant variations in the wave-particle complementarity relation.
We introduce a configuration‑dependent parametrisation of coherence in Wheeler’s delayed‑choice experiment based on the complex quantity T=t−iτ. The real component t retains its usual causal role, while the imaginary component τ encodes coherence attenuation without representing a physical time coordinate or an additional degree of freedom. Different interferometric configurations correspond to different decompositions of T, effectively acting as an internal rotation that modifies the imaginary‑time difference between paths and therefore the visibility. This mechanism alters coherence without affecting causal evolution and does not require retrocausality. The construction remains fully compatible with standard quantum mechanics: it preserves unitary evolution, the Born rule, and the structure of completely positive trace‑preserving maps, and is equivalent to a standard dephasing channel written in a compact parametrised form. The framework yields experimentally testable predictions for visibility modulation and temporal correlations, including a temporal CHSH protocol in which the departure from classical bounds arises from the configuration dependence of Δτ rather than from any modification of the underlying dynamics.
A theoretical unified interferometric framework is developed for interaction-free measurement (IFM) and delayed-choice (DC) experiments. The proposed model leads to a quantum circuit based architecture in which an ancillary qubit coherently controls the interaction between a photon and a bomb, allowing the system to evolve in a superposition of interaction and non-interaction regimes. The ancillary control qubit serves as a quantum switch that continuously interpolates between IFM and DC behavior, revealing a common operational origin for both phenomena. We demonstrate that both the phenomena can be realized within this framework through controlled quantum-gate operations. The analysis shows that the framework enables a continuous transition between the particle-like and wave-like behavior in DC setup. The framework is shown to be consistent with standard quantum mechanics, preserving unitary evolution, quantum superposition and the measurement postulate.
An operationally well-defined delayed-choice quantum-eraser experiment is proposed, realizing a genuine delayed choice within presently available quantum-optical technology. A multimode quantum memory supplies a controlled and verifiable delay, ensuring that the choice operation is applied strictly after the observation event. Electronic single-photon interference detection measurements furnish a direct statistical discriminator between the causal and informational coherence hypotheses, based solely on marginal detection statistics and without any post-selection.