Photon pairs, highly entangled in polarization have been generated under femtosecond laser pulse excitation by a type I crystal source, operating in a single arm interferometric scheme. The relevant effects of temporal walk-off existing in these conditions between the ordinary and extraordinary photons were experimentally investigated. By introducing a suitable temporal compensation between the two orthogonal polarization components highly entangled pulsed states were obtained.
Bell State Preparation using Pulsed Non-Degenerate Two-Photon Entanglement
报道了一个新颖的贝尔态制备实验。利用飞秒脉冲泵浦的\emph{nondegenerate}共线自发参量下转换制备了高纯度的Bell态。飞秒泵浦脉冲的使用{ \em does not}导致我们方案中量子干涉可见度的降低，其中不使用振幅的后选择和其他传统机制，例如使用薄的非线性晶体或窄带光谱滤波器。该方案的另一个显著特点是泵浦、信号和空闲波长都是可区分的，这对于量子通信非常有用。
We report measurements of time-frequency entangled photon pairs and heralded single photons at telecommunications wavelengths, generated using a periodically-poled, lithium niobate on insulator (LNOI) waveguide pumped optically by a diode laser. We achieve a high Coincidences-to-Accidentals Ratio (CAR) at high pair brightness, a low value of the conditional self-correlation function [$g^{(2)}$(0)], and high two-photon energy-time Franson interferometric visibility, which demonstrate the high quality of the entangled photon pairs and heralded single photons.
Delayed cavity-free forward lasing at the wavelengths of 391 and 428 nm was observed in recent experiments in air or pure nitrogen pumped with an intense femtosecond laser pulse at wavelength of 800~nm. The mechanism responsible for the lasing is highly controversial. In this article we explain the delayed emission by the presence of long-lived polarizations coupling simultaneously ground state X$^2Σ_g^+$ to states A$^2Π_u$ and B$^2Σ_u^+$ of singly ionized nitrogen molecules N$_2^+$. Ionization of neutral nitrogen molecules in a strong laser field and subsequent ion excitation are described by…
光学量子信息处理需要超亮的纠缠光子源，特别是来自可同步的飞秒激光器和低成本的连续波二极管激光器。由于定时信息和空间模式相关相位的退相干传统上限制了这样的源的亮度。我们报告了各种方法来优化I型偏振纠缠源-结合使用不同的补偿技术来设计高保真脉冲和连续波二极管激光泵浦源，以及直接从高度非线性双轴晶体BiB 3 O 6（BiBO）的偏振纠缠的第一次生产。使用空间补偿，我们在相位平坦度上显示了超过400倍的改善，否则会限制从BiBO有效收集纠缠光子，并报告了迄今为止任何超快偏振纠缠源的最高保真度（99%）。我们的数字代码，可在我们的网站上，可以设计最佳的补偿晶体和模拟纠缠从各种I型相位匹配的非线性晶体。
We study the generation of single photon perfect W-state. An important aspect of this perfect W-state is that, it can be used for perfect teleportation and superdense coding, which are not achievable with maximally entangled W-state. Our scheme for generation involves entanglement between various path degrees of freedom of a single photon in a compact and weakly coupled integrated waveguide system, which can be fabricated precisely with femtosecond laser direct writing technique. These platforms are interferometrically stable, scalable, less sensitive to decoherence and ensures a very low loss…
Optical quantum technologies such as quantum sensing, quantum cryptography and quantum computation all utilize properties of non-classical light, such as precise photon-number and entangled photon-pair states, to surpass technologies based on the classical light. A common route for obtaining heralded single photons is spontaneous four-wave mixing in optical fibers, allowing for a well-defined spatial mode, for high efficiency integration into optical fiber networks. These fibers are typically pumped using large, commercial, pulsed lasers requiring high-power (~10 W) pump lasers and are limited…
Multimode Squeezed State for Reconfigurable Quantum Networks at Telecommunication Wavelengths
ICFO - Instituto de Ciencias Fotonicas, The Barcelona Institute of Science and Technology（ICFO-光子科学研究所，巴塞罗那科学技术研究所）；Laboratoire Kastler Brossel, Sorbonne Université, ENS-Université PSL, CNRS, Collège de France（卡斯勒布罗塞尔实验室，索邦大学，巴黎文理研究大学，法国国家科学研究中心，法兰西公学院）；Sorbonne Université, LIP6, CNRS（索邦大学，LIP6实验室，法国国家科学研究中心）
Pulse-resolved post-generation phase control of squeezed light at 93 MHz with a bulk lithium-niobate modulator
Università degli Studi di Milano（米兰大学）；Istituto Nazionale di Fisica Nucleare, Sezione di Milano（意大利国家核物理研究所米兰分部）；Istituto di Fotonica e Nanotecnologie - CNR（光子与纳米技术研究所-意大利国家研究委员会）
