Laguerre Gaussian Beams Enable Gauge-Invariant Phase Mapping Via Closed-Loop Atomic Systems

The subtle interplay between light and matter reveals fundamental aspects of quantum mechanics, and researchers are continually seeking new ways to precisely control and measure light’s phase, a property crucial for technologies like optical communication and sensing. Nayan Sharma and Ajay Tripathi, both from Sikkim University, alongside their colleagues, now demonstrate a method for mapping phase information onto the intensity patterns of structured light beams using a unique atomic system. Their work establishes a clear link between a quantum property called gauge-invariant loop phase within a closed-loop atomic system and the resulting bright-dark lobes observed in the light’s intensity, offering a novel platform to explore geometric phases like the Berry phase and potentially leading to new precision measurement techniques. This achievement positions structured light within these closed-loop systems as an ideal environment for investigating these fundamental quantum phenomena, previously difficult to observe.

Absorption, a scattering term and loop phase dependent interference term with optical depth controlling visibility, characterise these systems. They enable mapping of arbitrary phases via interference rotation and offer a platform to measure Berry phase, a geometric holonomy acquired by dark states during adiabatic traversal of LG phase defined in a toroidal parameter space. Manifesting as fringe shifts absent in open systems, experimental realisation using cold atoms or solid state platforms appears feasible, positioning structured light in closed-loop systems as ideal testbeds for geometric phases in quantum optics.

Structured Light and Electromagnetically Induced Transparency

This research investigates the interplay between structured light and electromagnetically induced transparency (EIT) within closed-loop three-level atomic systems. Structured light, such as Laguerre-Gaussian beams, carries orbital angular momentum, a property that can be used to encode information or manipulate matter. EIT is a quantum phenomenon that allows light to pass through an otherwise opaque medium, often used to slow light or create nonlinear effects. The team focuses on how the phase of the light influences the transparency, creating a system where light interaction forms a closed loop in quantum transitions.

The study demonstrates how a closed-loop atomic system, driven by structured light, can control and measure geometric phases, specifically Berry phases. Researchers propose that the loop phase within the atomic system alters the intensity pattern of the output light, providing a means to observe and quantify these geometric phases. This approach relies on carefully controlling the light and atomic system parameters to observe shifts in interference fringes, revealing the Berry phase. Controlling and measuring geometric phases is crucial for advancements in quantum information processing, precision sensing, and optical manipulation. This work could contribute to developing new methods for encoding and manipulating quantum information, creating highly sensitive sensors, and achieving more precise control over microscopic objects. The principles explored may also lead to the development of novel optical devices with unique properties.

Loop Phase Imprints Beam Intensity Patterns

Scientists have theoretically demonstrated that a loop phase within a three-level atomic system creates distinct bright and dark lobes in the intensity pattern of a Laguerre-Gaussian probe beam. This establishes a connection between the system’s internal phase and the spatial characteristics of light, offering new possibilities for phase measurement and manipulation. The team modeled a closed-loop atomic system driven by light fields and analytically determined how the loop phase influences the output intensity. Experiments reveal that the output intensity comprises light absorption, scattering, and a crucial interference term dependent on the loop phase.

The magnitude of this interference term controls the visibility of the bright-dark lobes, enabling precise mapping of arbitrary phases through intensity variations. Measurements confirm that the system’s topology gives rise to a Berry phase, appearing as fringe shifts absent in open systems, making this setup ideal for investigating geometric phases. Calculations show that a Laguerre-Gaussian beam with a specific parameter setting produces a bright transmission lobe at one angle and a dark lobe at another when the loop phase is zero. Varying the optical depth, a measure of light-matter interaction, alters the intensity patterns, providing another parameter for control and analysis. This breakthrough delivers a platform for mapping and studying geometric phases, potentially impacting quantum information processing and precision metrology.

Loop Phase Imprinting and Berry Phase Measurement

This research presents an analytical model demonstrating how closed-loop three-level atomic systems imprint a loop phase onto the intensity patterns of Laguerre-Gaussian probe beams, manifesting as distinct bright-dark lobes. The team showed that the output intensity comprises contributions from light absorption, scattering, and a loop-phase dependent interference term, with optical depth playing a crucial role in the visibility of this interference. This work establishes a pathway for mapping arbitrary phases using controlled rotation of interference patterns, offering a novel approach to phase measurement. The study proposes a method for measuring the Berry phase, a geometric property acquired by dark states as they traverse a parameter space defined by the light beam’s phases.

This phase, absent in conventional open systems, appears as a measurable shift in interference fringes, suggesting these closed-loop systems are ideal for exploring geometric phases within structured light quantum optics. Realising this experimentally requires careful control of atomic systems to ensure weak probe conditions and adiabatic evolution, balancing the need to suppress transitions to bright states with the preservation of coherence. Future work will likely focus on identifying suitable atomic or solid-state platforms capable of meeting these demanding conditions, potentially utilising modern cold-atom technologies. While challenging, the team believes these constraints are within reach, opening promising avenues for investigating geometric phases and advancing the field of structured-light quantum optics. The findings contribute to a growing body of knowledge concerning structured light and its applications in areas such as optical communications and precision measurement.