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Quantum Communications and Quantum Imaging

Effect of anti-relaxation coatings on EIT-based quantum memory in Cs vapor cells

Changhoon Park, Jing Su, Stanley Hsu, Xiao Hong Tang, Thomas Gerrits, Oliver Slattery, Lijun Ma

Published Sep 18, 2025• 1 citation
Publisher

Abstract

Electromagnetically induced transparency (EIT) is a promising approach for implementing quantum memory, a key component of quantum communication networks. However, its storage time is limited by decoherence, primarily due to atomic motion. Anti-relaxation coatings can mitigate decoherence by minimizing atom-wall interactions. In this study, we experimentally investigate EIT-based quantum memory in cesium vapor cells with different anti-relaxation coatings. We compare the EIT characteristics and storage behavior across different coatings to assess their suitability for quantum memory applications.

DOI
10.1117/12.3063186

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Electromagnetically induced transparency (EIT) is a promising approach for implementing quantum memory, a key component of quantum communication networks. However, its storage time is limited by decoherence, primarily due to atomic motion. Anti-relaxation coatings can mitigate decoherence by minimizing atom-wall interactions. In this study, we experimentally investigate EIT-based quantum memory in cesium vapor cells with different anti-relaxation coatings. We compare the EIT characteristics and storage behavior across different coatings to assess their suitability for quantum memory applications.
Atomic vapor-cell quantum memories are key devices for quantum information science. Anti-relaxation coatings on the inner surface of the cell suppress ground-state dephasing caused by atom-wall collisions, thereby improving memory performance. Nevertheless, systematic performance comparisons of vapor-cell quantum memories with different anti-relaxation coatings under identical conditions remain limited. Here, we experimentally compare quantum-memory performance in cesium vapor cells with and without anti-relaxation coatings-uncoated, paraffin-coated, and alkene-coated-under otherwise identical conditions to assess coating-dependent effects. Using electromagnetically induced transparency (EIT) as the light storage protocol, we characterize transmission, memory efficiency, and storage lifetime. The alkene-coated cell yields the largest enhancement in retrieval efficiency-more than fourfold relative to the uncoated cell and more than twofold relative to the paraffin-coated cell-while exhibiting a modest (approximately 16%) increase in storage lifetime. These results provide a systematic benchmark for evaluating anti-relaxation coatings and for this instance, identify alkene coatings as an effective choice for improving retrieval efficiency in warm-vapor-cell memories.
Antirelaxation coatings in atomic vapor cells allow ground-state coherent spin states to survive many collisions with the cell walls. This reduction in the ground-state decoherence rate gives rise to ultranarrow-bandwidth features in electromagnetically induced transparency (EIT) spectra, which can form the basis of, for example, long-time scale slow and stored light, sensitive magnetometers, and precise frequency standards. Here we study, both experimentally and theoretically, how Zeeman EIT contrast and width in paraffin-coated rubidium vapor cells are determined by cell and laser-beam geometry, laser intensity, and atomic density. Using a picture of Ramsey pulse sequences, where atoms alternately spend ``bright'' and ``dark'' time intervals inside and outside the laser beam, we explain the behavior of EIT features in coated cells, highlighting their unique characteristics and potential applications.
We present a simulation-based quantum process tomography study of polarization-qubit storage in warm cesium vapor cells with different coatings. The model incorporates experimentally measured retrieval efficiency as a function of storage time and includes three noise mechanisms: signal-to-noise–induced depolarizing admixture, transverse coherence decay (T2) and longitudinal relaxation (T1). Simulated polarization-analyzer scans are used to reconstruct the affine Bloch map of the memory channel at each storage time. From the reconstructed process, we extract effective depolarization, dephasing, and amplitude-damping parameters and quantify their individual contributions to fidelity loss. The analysis reveals that dephasing dominates infidelity growth, while SNR-driven depolarization becomes increasingly relevant at low retrieval efficiency. Comparative results for uncoated, paraffin-coated, and alkene-coated cells demonstrate coatingdependent coherence preservation and provide a quantitative framework for separating incoherent noise mechanisms in warm-vapor quantum memories.