电信多芯光纤中光子数分辨量子光的模可调芯间耦合
Mode-tunable inter-core coupling of photon-number-resolved quantum light in a telecom multicore fiber
- Department of Physics, University at Buffalo, The State University of New York（纽约州立大学布法罗分校物理系）
- Science and Technology Division, Corning Research and Development Corporation（康宁研发公司科学与技术部）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
该研究在电信级39芯光纤中实现光子数分辨量子光的模可调芯间耦合，通过制备LP01-LP11相干叠加态，利用模式耦合速率差异实现3.9-13.1%的耦合调谐，并验证了传播的光子数无关性。
AI中文摘要：
多芯光纤（MCF）是为扩展经典电信容量而开发的，目前正作为高维密钥分发、纠缠和光子量子行走的量子平台而受到关注。迄今为止，量子光仅以单模路径通道的形式占据这些光纤；每个纤芯内的空间模结构尚未被触及。在此，我们在远离其设计波长的情况下运行一根电信级39芯光纤，其中每个纤芯恰好支持两个LP模式组（LP01、LP11），并测量宣布式光子数态|1>和|2>，同时分辨光子数与纤芯内空间模式或纤芯索引。位移发射制备了一个相干的LP01-LP11叠加态，其单侧强度图样表明模间相位在光纤中得以保持：漂移分辨联合拟合给出的像素不对称性（0.4%对47%）与不相干模式混合不相容。由于这两种模式以不同速率耦合到邻近纤芯（kappa_LP11/kappa_LP01 = 2.4），发射的模式内容充当了状态可选的耦合旋钮：无源光纤的有效芯间耦合仅由发射设置（3.9-13.1%），这种可调性否则需要电光、热光或机械重构。传播与光子数无关：宣布式|2>态的单光子串扰等于|1>态，将任何福克态依赖性限制在|dx/x| < 6.1%（95%置信水平），且|1>和|2>的成像模式分布一致性优于1%。这一测得的线性光学零点，经精确福克空间模拟验证，是光纤量子行走中真实多光子干涉必须认证的基线；我们还展示了如果未扣除偶然符合，基于符合的事件选择如何产生虚假的光子数依赖性串扰。
英文摘要：
Multicore optical fibers (MCFs), developed to scale classical telecommunications, are gaining traction as a quantum platform for high-dimensional key distribution, entanglement, and photonic quantum walks. So far, quantum light has occupied these fibers only as single-mode path channels; the spatial-mode structure within each core has remained untouched. Here we operate a telecom-grade 39-core fiber far from its design wavelength, where each core supports exactly two LP mode groups (LP01, LP11), and measure heralded photon-number states |1> and |2>, resolving the photon number simultaneously with the intra-core spatial mode or with the core index. Displacing the launch prepares a coherent LP01-LP11 superposition whose single-sided intensity pattern shows that the intermodal phase is preserved over the fiber: a drift-resolved joint fit gives a pixel asymmetry (0.4% vs 47%) incompatible with an incoherent mode mixture. Because the two modes couple to neighboring cores at different rates (kappa_LP11/kappa_LP01 = 2.4), the launched mode content acts as a state-selectable coupling knob: the effective inter-core coupling of the passive fiber is set by the launch alone (3.9-13.1%), a tunability that otherwise requires electro-optic, thermo-optic, or mechanical reconfiguration. The propagation is photon-number independent: the per-photon crosstalk of heralded |2> states equals that of |1>, bounding any Fock-state dependence to |dx/x| < 6.1% (95% CL), and the imaged mode distributions of |1> and |2> agree to better than 1%. This measured linear-optics null, validated against exact Fock-space simulation, is the baseline against which genuine multiphoton interference in fiber quantum walks must be certified; we also show how coincidence-based event selection produces spurious photon-number-dependent crosstalk if accidentals are not subtracted.
