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Journal of Applied Physics

Quantum coherence and tunneling-controlled spatial localization in a three-level quantum dot system

Muhammad Idrees, Fazal Badshah, Zareen Abdulhameed Khan

Published Jan 22, 2026• 1 citation
Publisher

Abstract

We investigate spatial localization and interference control in a three-level quantum dot (QD) system driven by two-dimensional standing-wave fields. Although QDs are embedded in solid-state environments and are heavier than natural atoms, their discrete energy levels and tunable tunneling couplings allow them to replicate atomic-like behaviors, offering greater flexibility than traditional atomic systems. Using the density matrix formalism, we calculate the optical susceptibility under the influence of a weak probe and a strong control field. This susceptibility explicitly incorporates inter-dot tunneling and phase-coherent interactions, ensuring that the resulting localization is not merely a classical field imprint but reflects quantum interference effects. Our results show that while the standing-wave fields define the spatial modulation template, the accuracy, contrast, and stability of localization are primarily determined by quantum coherence and tunneling-induced interference. Symmetric wavevector configurations lead to sharply confined, isotropic localization profiles, whereas asymmetries in wavevector alignments cause the distribution to broaden and degrade, reducing localization precision. These findings highlight the critical role of tunneling coherence and wavevector alignment in controlling localization behavior. The observations suggest that QDs, with their tunable energy levels and tailored tunneling couplings, provide versatile solid-state analogs for exploring localization phenomena. These systems hold significant potential for applications in spatially resolved quantum information processing, nanoscale sensing, and the development of coherent nanophotonic devices.

DOI
10.1063/5.0301182

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We investigate spatial localization and interference control in a three-level quantum dot (QD) system driven by two-dimensional standing-wave fields. Although QDs are embedded in solid-state environments and are heavier than natural atoms, their discrete energy levels and tunable tunneling couplings allow them to replicate atomic-like behaviors, offering greater flexibility than traditional atomic systems. Using the density matrix formalism, we calculate the optical susceptibility under the influence of a weak probe and a strong control field. This susceptibility explicitly incorporates inter-dot tunneling and phase-coherent interactions, ensuring that the resulting localization is not merely a classical field imprint but reflects quantum interference effects. Our results show that while the standing-wave fields define the spatial modulation template, the accuracy, contrast, and stability of localization are primarily determined by quantum coherence and tunneling-induced interference. Symmetric wavevector configurations lead to sharply confined, isotropic localization profiles, whereas asymmetries in wavevector alignments cause the distribution to broaden and degrade, reducing localization precision. These findings highlight the critical role of tunneling coherence and wavevector alignment in controlling localization behavior. The observations suggest that QDs, with their tunable energy levels and tailored tunneling couplings, provide versatile solid-state analogs for exploring localization phenomena. These systems hold significant potential for applications in spatially resolved quantum information processing, nanoscale sensing, and the development of coherent nanophotonic devices.
This study investigates the tunable propagation of optical pulses in a three-level system of coupled quantum dots. The system forms an effective closed configuration, supporting strong quantum coherence and controllable light–matter interactions. Using the density matrix formalism, we analyze the quantum dynamical response under the influence of both a weak probe and a strong control field, with inter-dot tunneling acting as a key tunable parameter. Our results reveal that both the tunneling strength (Te) and control field Rabi frequency (Ωc) play crucial roles in shaping the system’s optical properties. We observe the emergence of electromagnetically induced transparency-like windows, the splitting and shifting of dispersion peaks, and the formation of absorption doublets and transparency windows. The real and imaginary parts of the electric permittivity exhibit pronounced sensitivity to these external controls. Furthermore, the group index and group velocity are shown to be highly tunable, enabling transitions between slow-light and fast-light regimes. Detailed analysis of temporal pulse dynamics demonstrates the ability to achieve controllable delay and advancement of optical pulses, depending on the interaction between Te and Ωc. These findings highlight the potential of such quantum dot systems for dynamic photonic control, including applications in optical buffering, reconfigurable delay lines, coherent switching, and quantum information processing. The demonstrated tunability and coherence effects make this platform a promising candidate for next-generation optoelectronic and quantum photonic technologies.
We present an alternative scheme for the preparation of the phase grating in quantum-dot molecules, where the tunnel coupling occurs between two quantum dots. In the presence of interdot tunneling, the nonlinear dispersion can be significantly enhanced with nearly vanishing linear and nonlinear absorption due to the tunneling-induced quantum coherence. With the help of a standing-wave control field, the weak probe light could be diffracted into high-order direction. It is shown that parameters such as the weak-driving intensity, driving detuning, tunneling strength, and interaction length could be used to adjust the diffraction intensity effectively. Our scheme is focused on the weak standing-wave driving and weak tunneling strength, which may provide an easy and actual way to obtain the phase grating and may have potential applications in quantum-optics and quantum-information-processing devices in the solid-state system.
Abstract We propose a new scheme for high-precision three-dimensional (3D) atom localization by observing the spatially modulated absorption of a weak probe field operating in a partially closed-loop dependent five-level atomic system. Different spatial structures of localization patterns are presented by controlling the Rabi frequency, detuning, and field-induced collective phase-coherence with a variety of superposed standing wave field configurations. Our results highlight that 100% detection probability of atom is possible in the present model in many ways with high precision measurement of spatial absorption. It has been shown that, in the presence of standing wave fields, position information of the atom with maximum detection probability can be efficiently controlled by employing the travelling-wave field in the system. In the present work, we note that the maximum detection probability of the atom is attainable with the limit of spatial resolution better than λ/50. The efficacy of the present model is to find its application in atom nanolithography and atom-imaging having importance in quantum information processing.
We manipulate the coupling effect between interdot tunneling and the external control field to study the optical diffractive property in a quantum dot molecule (QDM) system. Based on the density matrix approach, an analytical relation is obtained for the optical susceptibility, which shows tunneling-induced transparency (TIT) in the absorption spectra. We propose an innovative optoelectronic device called tunneling-induced grating, which operates based on the diffraction of the forward-transmitted probe laser light. The diffraction integrals for the far-field regime (i.e., Fraunhofer diffraction) are numerically solved, and the effect of interdot tunneling coupling strength on the diffraction patterns is studied. It is shown that the transmission is increased under tunneling-induced quantum coherence. The weak probe light can be diffracted into higher-order directions upon applying a standing-wave control field. The optimal parametric condition for maximum first- and second-order diffractions is obtained. The results find the potential applications in quantum information processing devices, such as all-optical grating and switches at low light levels.
We propose a efficient scheme for high-precision three-dimensional (3D) atom localization via spatial interference in a generic double two-level atomic system driven by a weak probe field and three mutually perpendicular standing-wave fields. Because the spatial interference originates from the position-dependent atom-field interaction, the position information of the atom can be obtained by the measurement of the atom population. We find that the precision of 3D atom localization in volumes depends sensitively on the frequency detuning and the phase shifts associated with the standing-wave fields. Interestingly enough, we show that adjusting the frequency detuning and phase shifts can lead to a redistribution of the atoms and a significant change in the visibility of the interference pattern. As a result, the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength.
We present a comprehensive theoretical investigation of two-dimensional (2D) Compton-azimuthal atomic localization in a three-level atomic system interacting with spatially structured light fields. The study focuses on how the azimuthal quantum numbers of the applied standing-wave fields influence the spatial probability distribution of an atom within the 2D plane. By numerically solving the governing equations of motion with realistic atomic parameters, we obtain localization maps that reveal sharp and well-defined probability peaks. The spatial localization arises from the position-dependent Rabi frequencies, which are modulated by the standing-wave interference patterns and the orbital angular momentum carried by the fields. Our results demonstrate a clear transition from multiple sharp localization peaks to a single dominant peak as ℓ1 and ℓ2 are reduced. This peak reduction significantly increases the probability of finding the atom at the remaining high-probability sites, reaching 100% localization probability in the single-peak regime. Physically, this occurs because lower azimuthal mode numbers simplify the spatial interference structure, concentrating the atomic wavefunction in a narrower spatial region. The tunability of localization via ℓ1 and ℓ2 provides a flexible control mechanism for atomic position measurement with subwavelength precision. The findings not only offer new insights into Compton-azimuthal localization mechanisms but also open potential applications in quantum metrology, atom-based nanolithography, and precision quantum control of matter–light interactions in structured optical fields.