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Research in Optical Sciences

Imaging via Quantum Indistinguishability of Undetected Photons

Gabriela Barreto Lemos, Victoria Borish, Garrett D. Cole, Sven Ramelow, Radek Łapkiewicz, Anton Zeilinger

Published Jan 1, 2014• 0 citations
Publisher

Abstract

Indistinguishability of photons that need not be detected results in a novel paradigm of quantum information processing. This confirms that for quantum interference it is important whether two possibilities could in principle be distinguished independent of detection.
DOI
10.1364/qim.2014.qtu1a.1

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QUANTUM IMAGING WITH UNDETECTED PHOTONS AND THE THEORY OF OBJECTIVITY

Vidamor Cabannas

This article develops an expanded critical–propositional analysis of Gabriela Barreto Lemos et al.’s experiment, “Quantum Imaging with Undetected Photons,” published in Nature 512 (2014): 409–412, DOI 10.1038/nature13586, in systematic dialogue with the Theory of Objectivity (TO) formulated by Vidamor Cabannas and Denivaldo Silva. Lemos et al. experimentally demonstrated an imaging architecture based on induced coherence without induced emission in which photons that interact with an object are not themselves detected, whereas the image is reconstructed exclusively by detecting photons that never interacted directly with that object. Two coherently pumped nonlinear crystals can produce signal–idler photon-pair alternatives. An idler originating from the first crystal traverses the object and is subsequently mode- matched with the idler alternative associated with the second crystal. Under conditions in which the origin of the generated pair remains physically indistinguishable, the signal alternatives interfere, and amplitude and phase information introduced into the undetected idler path becomes accessible through the detected signal intensity (Lemos et al., 2014; Lahiri et al., 2015). The experiment therefore provides an unusually productive empirical domain in which to examine relations among interaction, physical distinguishability, coherence, information, observation, boundaries, and compositional phenomena. The present study argues that Lemos et al. do not experimentally establish the complete ontology of the Theory of Objectivity and do not demonstrate the modal necessity of its Seven Absolute Truths. Nevertheless, the experiment provides important operational bridges to the Fourth, Fifth, Sixth, and Seventh Absolute Truths when these propositions are carefully distinguished from stronger metaphysical interpretations. Particular attention is devoted to the Fifth Absolute Truth, according to which an element must, for logical existence, be observed or remain within the frequency of at least two other elements, where “observation” does not mean human consciousness. Quantum imaging with undetected photons provides an experimentally controlled domain in which observable manifestation depends on relations among multiple phys- ical systems independently of a conscious observer. The later theoretical analysis of the Lemos architecture showed that information about the object occurs in the interference contribution rather than in either individual signal intensity considered separately (Lahiri et al., 2015). This makes the experiment particularly relevant to a TO interpretation of information as fundamentally relational. Methodological restraint is nevertheless essential. Classical-state correlated optical systems can reproduce important operational features of imaging with unde- tected photons (Shapiro, Venkatraman, and Wong, 2015). Consequently, the Lemos experiment does not by itself discriminate between the ontology of the TO and all competing descriptions. Its strongest scientifically defensible role is therefore to provide a controlled experimental environment in which TO propositions concerning relational existence, physical boundaries, non-human observation, composition, and information may be translated into measurable quantities. The article concludes by proposing an empirical research program in which modal propositions of the TO are related to experimentally measurable parameters such as distinguishability, coherence, visibility, complex transmission, boundary transformation, and recoverable information. Such a program could move the TO from conceptual compatibility with quantum phenomena toward genuinely discriminating empirical predictions. Keywords: Theory of Objectivity; quantum imaging; undetected photons; induced co- herence; quantum information; relational information; observation; indistinguishability; modal ontology; physical boundaries; testability; transcendent information.

•Sep 22, 2026•0 citations
Quantum imaging with undetected photons (QIUP) is a promising technique for non-invasive imaging, particularly at wavelengths where detectors are inefficient or unavailable. Recent studies have investigated the role of polarization in QIUP schemes. In this work, we examine whether post-generation optical elements can recover interference when the signal photons are distinguishable in polarization at the source. Specifically, we employ a Mach-Zehnder interferometer after the photon pairs are generated from two nonlinear crystals. Our results indicate that polarization distinguishability at the time of generation leads to a loss of interference that cannot be restored by post-generation optical arrangements. This highlights the fundamental importance of indistinguishability at the source for maintaining coherence in QIUP systems.
Imaging with undetected photons (IUP) enables the possibility of sensing changes in the phase and the transmission of a beam of light that need never be detected. This has led to the possibility of infrared sensing with visible silicon camera technology, for example. Relying on the interference of two identical pairs of photons, IUP was initially achieved using unidirectional paths through two nonlinear crystal pair sources. More recently, folded arrangements using bidirectional paths through a single-crystal have become common for their simplicity. Here, we theoretically model and experimentally implement a novel setup involving three interference paths through a single nonlinear crystal. This establishes two independent IUP sensing modes in addition to a third linear interference mode. We achieve this using a polarization state quantum eraser approach, with excellent agreement between experiment and theory. This system provides a new route to control and optimize IUP interference in a single-crystal folded arrangement by using controllable quantum erasure to balance the interferometer, opening the door to new implementations and applications for IUP.
This article develops an expanded critical–propositional analysis of Gabriela Barreto Lemos et al.’s experiment, “Quantum Imaging with Undetected Photons,” published in Nature 512 (2014): 409–412, DOI 10.1038/nature13586, in systematic dialogue with the Theory of Objectivity (TO) formulated by Vidamor Cabannas and Denivaldo Silva. Lemos et al. experimentally demonstrated an imaging architecture based on induced coherence without induced emission in which photons that interact with an object are not themselves detected, whereas the image is reconstructed exclusively by detecting photons that never interacted directly with that object. Two coherently pumped nonlinear crystals can produce signal–idler photon-pair alternatives. An idler originating from the first crystal traverses the object and is subsequently mode- matched with the idler alternative associated with the second crystal. Under conditions in which the origin of the generated pair remains physically indistinguishable, the signal alternatives interfere, and amplitude and phase information introduced into the undetected idler path becomes accessible through the detected signal intensity (Lemos et al., 2014; Lahiri et al., 2015). The experiment therefore provides an unusually productive empirical domain in which to examine relations among interaction, physical distinguishability, coherence, information, observation, boundaries, and compositional phenomena. The present study argues that Lemos et al. do not experimentally establish the complete ontology of the Theory of Objectivity and do not demonstrate the modal necessity of its Seven Absolute Truths. Nevertheless, the experiment provides important operational bridges to the Fourth, Fifth, Sixth, and Seventh Absolute Truths when these propositions are carefully distinguished from stronger metaphysical interpretations. Particular attention is devoted to the Fifth Absolute Truth, according to which an element must, for logical existence, be observed or remain within the frequency of at least two other elements, where “observation” does not mean human consciousness. Quantum imaging with undetected photons provides an experimentally controlled domain in which observable manifestation depends on relations among multiple phys- ical systems independently of a conscious observer. The later theoretical analysis of the Lemos architecture showed that information about the object occurs in the interference contribution rather than in either individual signal intensity considered separately (Lahiri et al., 2015). This makes the experiment particularly relevant to a TO interpretation of information as fundamentally relational. Methodological restraint is nevertheless essential. Classical-state correlated optical systems can reproduce important operational features of imaging with unde- tected photons (Shapiro, Venkatraman, and Wong, 2015). Consequently, the Lemos experiment does not by itself discriminate between the ontology of the TO and all competing descriptions. Its strongest scientifically defensible role is therefore to provide a controlled experimental environment in which TO propositions concerning relational existence, physical boundaries, non-human observation, composition, and information may be translated into measurable quantities. The article concludes by proposing an empirical research program in which modal propositions of the TO are related to experimentally measurable parameters such as distinguishability, coherence, visibility, complex transmission, boundary transformation, and recoverable information. Such a program could move the TO from conceptual compatibility with quantum phenomena toward genuinely discriminating empirical predictions. Keywords: Theory of Objectivity; quantum imaging; undetected photons; induced co- herence; quantum information; relational information; observation; indistinguishability; modal ontology; physical boundaries; testability; transcendent information.