标题： 双光束在热碱金属原子中通过光学参量放大生成的隐藏纠缠 显示英文标题

标题： Hidden entanglement in twin beams generated through optical parametric amplification in hot alkali atoms

摘要： 对多模光态中量子关联的正确表征对于量子信息科学的应用至关重要；然而，最常见的纠缠测量可能导致状态重建不完整。 这是对于场正交分量的普遍频谱测量的情况，对于这种测量，无法完全表征光学束之间的量子关联。 我们通过在热铷蒸气中通过四波混频产生的孪生光束来演示这一效应，展示了频率依赖增益响应的作用。 我们实施了一种基于谐振器的测量方法，揭示了通常频谱测量所隐藏的光束之间的纠缠。 此外，该系统展示了所涉及场的载波和边带之间的相位偏移如何影响不同纠缠判据的观测结果，证明了进行完整状态层析的重要性。 显示英文摘要

摘要： Proper characterization of quantum correlations in a multimode optical state is critical for applications in quantum information science; however, the most common entanglement measurements can lead to an incomplete state reconstruction. This is the case for the ubiquitous spectral measurement of field quadratures for which a full characterization of the quantum correlations between optical beams is not possible. We demonstrate this effect in twin beams generated through parametric amplification by four-wave mixing in hot rubidium vapor, showing the role of a frequency dependent gain response. We implement a resonator-based measurement that reveals entanglement between beams that is otherwise hidden by usual spectral measurements. Additionally, this system shows how the phase shifts between the carrier and the sidebands on the involved fields affect the observation of entanglement for different entanglement witnesses, demonstrating the relevance of making a complete state tomography.