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The Coherence of Light Emitted by a Linear Coulomb Crystal and Its Mirror Image

Adam Čepil

Published Jan 1, 2023• 0 citations
OpenAlex

Abstract

In our work, we focus on the experimental demonstration of two complementary approaches to enhancing the interaction between photons and atoms at the level of individual photons and 40Ca+ ions. We implement a scheme in which the observation of light interference scattered by several trapped atomic ions is further enhanced due to interference with their mirror images. The control of the corresponding collective coherent optical scattering and the possibility of observing the interaction with light emitted by many independent ions modified by optical boundary conditions promises a feasible approach to the effective realization of the interaction between light and matter or to the controlled observation of quantum electrodynamics phenomena with many atoms.

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Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)•Jun 1, 2009•1 citation
In our work, we focus on the experimental demonstration of two complementary approaches to enhancing the interaction between photons and atoms at the level of individual photons and 40Ca+ ions. We implement a scheme in which the observation of light interference scattered by several trapped atomic ions is further enhanced due to interference with their mirror images. The control of the corresponding collective coherent optical scattering and the possibility of observing the interaction with light emitted by many independent ions modified by optical boundary conditions promises a feasible approach to the effective realization of the interaction between light and matter or to the controlled observation of quantum electrodynamics phenomena with many atoms.
The efficient detection of light from trapped ions in free space is paramount for most of their applications. We propose a scheme to enhance the photon collection from linear ion strings. It employs the constructive interference of light scattered from ions along the axial direction in linear Paul traps. The coherent enhancement of photon collection is numerically optimized for a range of feasible spatial angles and realistic ion positions in a single harmonic Coulomb potential. Despite the large mutual distance of scatterers on the order of many wavelengths of scattered light, the experimental tests presented confirm the feasibility of enhancements by a factor of 3.05 ± 0.09 with a crystal of nine 40Ca+ ions. The proposed collection geometry is intrinsic to diverse linear ion trap designs, and the methodology can be directly applied to an observation of scattering from ion crystals prepared in collective electronic excitations. The presented data resulted from measurements supported by national funding from the Ministry of Education, Youth and Sports under grant agreement No. 731473, by the QUANTERA ERA-NET cofund in quantum technologies implemented within the European Union’s Horizon 2020 Program (project PACE-IN, 8C20004), by the Czech Science Foundation under the project GA21-13265X, the Ministry of Education, Youth and Sports under the project CZ.02.01.01/00/22 008/0004649, the Ministry of Interior of the Czech Republic within the Program OPSEC under the project VK01030193, and the Palacký University grant IGA-PrF-2024-008.
The demonstration of coherence between a large number of quantum emitters is essential for the realization of many paradigmatic experiments in quantum optics. Here we present the observation of controlled interference of light scattered from crystal strings of up to 53\,trapped ions. The scattered light is collected along the crystal symmetry axis, which guarantees spatial indistinguishability of photons scattered by different ions and allows for convenient scaling of the number of contributing particles. The interference phase is tuned by changing the mutual distance between the ions and the observed pattern corresponds qualitatively to a simple theoretical model considering point-like emitters. The observed interference visibility remains in the 0.34 to 0.53 range for all the measured string sizes, limited mostly by the spatially inhomogeneous laser intensity seen by the long ion strings. The presented results open the possibility for experimental investigation of a whole range of fundamental physical phenomena, including engineered directional photon emission, direct detection of quadrature squeezing of atomic resonance fluorescence, and optical generation of genuine multi-partite entanglement between a large number of trapped ions.
The efficient detection of light from trapped ions in free space is paramount for most of their applications. We propose a scheme to enhance the photon collection from linear ion strings. It employs the constructive interference of light scattered from ions along the axial direction in linear Paul traps. The coherent enhancement of photon collection is numerically optimized for a range of feasible spatial angles and realistic ion positions in a single harmonic Coulomb potential. Despite the large mutual distance of scatterers on the order of many wavelengths of scattered light, presented experimental tests confirm the feasibility of enhancements by a factor of 3.05±0.093.05 \pm 0.093.05±0.09 with a crystal of nine 40^{40}40Ca+^++ ions. Further significant improvements using different ion species, which allow for suppression of the sensitivity to the residual thermal motion, are predicted. The proposed collection geometry is intrinsic to diverse linear ion trap designs and the methodology can be directly applied to an observation of scattering from ion crystals prepared in collective electronic excitations.
Abstract The efficient detection of light from trapped ions in free space is paramount for most of their applications. We propose a scheme to enhance the photon collection from linear ion strings. It employs the constructive interference of light scattered from ions along the axial direction in linear Paul traps. The coherent enhancement of photon collection is numerically optimized for a range of feasible spatial angles and realistic ion positions in a single harmonic Coulomb potential. Despite the large mutual distance of scatterers on the order of many wavelengths of scattered light, the experimental tests presented confirm the feasibility of enhancements by a factor of 3.05 ± 0.09 with a crystal of nine 40 Ca + ions. The proposed collection geometry is intrinsic to diverse linear ion trap designs, and the methodology can be directly applied to an observation of scattering from ion crystals prepared in collective electronic excitations.
While the spontaneous emission from independent emitters provides spatially uncorrelated photons-a typical manifestation of quantum randomness, the interference of the coherent scattering leads to a well-defined intensity pattern-a feature described by linear optics. We here demonstrate experimentally how the interplay between the two mechanisms in large systems of quantum emitters leads to spatial variations of photon correlations. The implementation with trapped ion crystals in free space allows us to observe the anticorrelation between photon rates and variance of the photon number distributions in chains of up to 18 ions. For smaller crystals of four ions, the transition from antibunching to bunching and super-Poissonian statistics of the scattered light is reported. For higher numbers of scatterers, the photon statistics still display a strong deviation from the fully incoherent scattering case. Our results illustrate how the interference of coherent scattering, combined with spontaneous emission, provides a control mechanism for the light statistics.
Cavity Quantum Electrodynamics (CQED) is an attractive platform for the realization of efficient light-matter quantum interfaces at the single photon level. Such interfaces are key elements for the development of quantum information and communication science due to the need for swapping information between flying and stationary qubits. Here, we report on the first CQED demonstration of collective strong coupling between atomic ions in a solid in the form of an ion Coulomb crystal and an optical field [1].