Brazilian Twin Photons 32nd anniversary

TL;DR

This historical review documents over three decades of spontaneous parametric down-conversion research in Brazil, tracing the emergence of a robust twin-photon program beginning with UFMG and expanding through multiple institutions. It highlights a progression from foundational laboratory development to sophisticated spatial-entanglement experiments, including angular-spectrum transfer, nonlocal interference, OAM conservation, and non-Gaussian entanglement, culminating in studies of decoherence dynamics and non-Markovian effects. The work emphasizes the creation of a dense research network, significant international influence, and ongoing efforts to translate fundamental twin-photon phenomena into quantum information applications. Collectively, the Brazilian program demonstrates how resourceful experimental design and theory–experiment collaboration can drive both foundational understanding and practical quantum technologies.

Abstract

We present a historical review of the development and impact of spontaneous parametric down-conversion (SPDC) in Brazil, marking over three decades since the first twin-photon experiments were performed in the country. This article traces the pioneering efforts that initiated the field, highlighting key experiments, institutions, and researchers who contributed to its growth. We discuss seminal works that established SPDC as a fundamental tool in the Brazilian Quantum Optics community, including studies on spatial correlations, entanglement, and decoherence. By presenting a curated sequence of experiments, we offer an overview of how Brazilian research in twin-photon systems has explored profound concepts through fundamental demonstrations, leading to significant international impact. This review also highlights the formation of a strong scientific community and its ongoing efforts to turn fundamental knowledge into quantum applications.

Figures (19)

• Figure 1: Photon ricochet in a cavity: measurement of the photon time of flight in a non-interfering linear cavity monken93. a) Conceptual representation of the experimental setup and b) results.
• Figure 2: Nonlocal control of spatial coherence: a) Conceptual representation of the experimental setup and b) results extracted from article ph94. The coincidence counts show the interference pattern for different diameters of pinhole.
• Figure 3: Transfer of the angular spectrum: conceptual representation of the experimental setup and results. Measurement of the transfer of the angular spectrum from the pump to the quantum correlations monken98.
• Figure 4: Nonlocal double slit: a) Conceptual representation of the experimental setup and b) the results extracted from Ref. fonseca99.
• Figure 5: Multiphoton de Broglie wavelength: conceptual representation of the a) experimental setup and results, and b) measurement of the DeBroglie wavelength of a biphoton fonseca99b.