Highly efficient generation of pulsed photon pair using a bulk Periodically Poled Potassium Titanyl Phosphate

Broadband pumped polarization entangled photon-pair source in a linear beam displacement interferometer

We experimentally demonstrate a source of polarization entangled photon-pairs based on a single periodically-poled potassium titanyl phosphate (PPKTP) crystal pumped with a broadband, free running laser diode.The crystal is placed within a linear beam-displacement interferometer, and emits photon-pairs based ontype-0 spontaneous parametric downconversion (SPDC). We observe pair rates of 0.56 Mpairs/s/mW in a single spatial mode with a polarization visibility of 97.7% over a spectral range of 100 nm. This experiment demonstrates a pathway towards observing Gigacount rates of polarization entang…

High-visibility nonclassical interference of photon pairs generated in a multimode nonlinear waveguide

We report measurements of two-photon interference using a cw-pumped type-II spontaneous parametric down-conversion source based on a multimode perodically poled potassium titanyl phosphate waveguide. We have used the recently demonstrated technique of controlling the spatial characteristics of the down-conversion process via intermodal dispersion to generate photon pairs in fundamental transverse modes, thus ensuring their spatial indistinguishability. Good spatial overlap of photon modes within pairs has been verified using the Hong-Ou-Mandel interferometer and the preparation of polarization…

A high-brightness source of polarization-entangled photons optimized for applications in free space

We present a simple but highly efficient source of polarization-entangled photons based on spontaneous parametric down-conversion (SPDC) in bulk periodically poled potassium titanyl phosphate crystals (PPKTP) pumped by a 405 nm laser diode. Utilizing one of the highest available nonlinear coefficients in a non-degenerate, collinear type-0 phase-matching configuration, we generate polarization entanglement via the crossed-crystal scheme and detect 0.64 million photon pair events/s/mW, while maintaining an overlap fidelity with the ideal Bell state of 0.98 at a pump power of 0.025 mW.

Pulsed source of spectrally uncorrelated and indistinguishable photons at telecom wavelengths

We report on the generation of indistinguishable photon pairs at telecom wavelengths based on a type-II parametric down conversion process in a periodically poled potassium titanyl phosphate (PPKTP) crystal. The phase matching, pump laser characteristics and coupling geometry are optimised to obtain spectrally uncorrelated photons with high coupling efficiencies. Four photons are generated by a counter- propagating pump in the same crystal and anlysed via two photon interference experiments between photons from each pair source as well as joint spectral and g^(2) measurements. We obtain a spec…

Scheme for on-chip verification of transverse mode entanglement using the electro-optic effect

A key ingredient in emerging quantum-enhanced technologies is the ability to coherently manipulate and detect superpositions of basis states. In integrated optics implementations, transverse spatial modes supported by multimode structures offer an attractive carrier of quantum superpositions. Here we propose an integrated dynamic mode converter based on the electro-optic effect in nonlinear channel waveguides for deterministic transformations between mutually non-orthogonal bases of spatial modes. We theoretically show its capability to demonstrate a violation of a Bell-type Clauser-Horne-Shim…

Heralded single-photon source utilizing highly nondegenerate, spectrally factorable spontaneous parametric downconversion

We report on the generation of an indistinguishable heralded single-photon state, using highly nondegenerate spontaneous parametric downconversion (SPDC). Spectrally factorable photon pairs can be generated by incorporating a broadband pump pulse and a group-velocity matching (GVM) condition in a periodically-poled potassium titanyl phosphate (PPKTP) crystal. The heralding photon is in the near IR, close to the peak detection efficiency of off-the-shelf Si single-photon detectors; meanwhile, the heralded photon is in the telecom L-band where fiber losses are at a minimum. We observe spectral f…

Bright source of spectrally uncorrelated polarization-entangled photons with nearly single-mode emission

We present results of a bright polarization-entangled photon source operating at 1552 nm via type-II collinear degenerate spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate crystal. We report a conservative inferred pair generation rate of 123,000 pairs/s/mW into collection modes. Minimization of spectral and spatial entanglement was achieved by group velocity matching the pump, signal and idler modes and through properly focusing the pump beam. By utilizing a pair of calcite beam displacers, we are able to overlap photons from adjacent down-conversion p…

Generation of spatially pure photon pairs in a multimode nonlinear waveguide using intermodal dispersion

We present experimental realization of type-II spontaneous parametric down-conversion in a periodically poled potassium titanyl phosphate (KTiOPO4) nonlinear waveguide. We demonstrate that by careful exploitation of intermodal dispersion in the waveguide it is feasible to produce photon pairs in well defined transverse modes without any additional spatial filtering at the output. Spatial characteristics is verified by measurements of the M2 beam quality factors. We also prepared a postselected polarization-entangled two-photon state shown to violate Bell's inequality. Similar techniques based …

紧凑且稳定的极化纠缠光子对源基于折叠的线性位移干涉仪

Compact and stable source of polarization-entangled photon-pairs based on a folded linear displacement interferometer

基于折叠线性位移干涉仪的紧凑稳定极化纠缠光子对源，利用自发参量下转换实现高保真度和高效率的量子通信应用。

用于大规模量子信息处理的具有长相干时间的纯态光子对源

Pure-state photon-pair source with a long coherence time for large-scale quantum information processing

本文提出在PPKTP晶体中通过选择合适泵浦激光和滤波器生成具有长相干时间的纯态光子对源方案，实验演示了780nm光子对源并实现超过经典极限的HOM干涉，为大规模量子网络应用提供潜力。

通过单畴KTiOPO$_4$中的非临界相位匹配产生高度非简并的偏振纠缠光子对

Highly nondegenerate polarization-entangled photon pairs produced through noncritical phasematching in single-domain KTiOPO$_4$

本文提出并演示了一种基于单畴磷酸钛氧钾（KTP）中非临界相位匹配（NCPM）自发参量下转换（SPDC）的简单稳定方案，用于产生高度非简并的偏振纠缠光子对，在75°C晶体温度范围内闲频光中心波长变化10.8nm且纠缠可见度保持在98%以上，并通过62km和93km光纤传输实现了高可见度。

Highly-efficient generation of coherent light at 2128 nm via degenerate optical-parametric oscillation

Cryogenic operation in conjunction with new test-mass materials promises to reduce the sensitivity limitations from thermal noise in gravitational-wave detectors. The currently most advanced materials under discussion are crystalline silicon as a substrate with amorphous silicon-based coatings. They require, however, operational wavelengths around 2 $\mathrmμ$m to avoid laser absorption. Here, we present a light source at 2128 nm based on a degenerate optical parametric oscillator (DOPO) to convert light from a 1064 nm non-planar ring-oscillator (NPRO). We achieve an external conversion effici…

Efficient 525nm laser generation in single or double resonant cavity

This paper reports the results of a study into highly efficient sum frequency generation from 792 and 1556 nm wavelength light to 525 nm wavelength light using either a single or double resonant ring cavity based on a periodically poled potassium titanyl phosphate crystal (PPKTP). By optimizing the cavity$'$s parameters, the maximum power achieved for the resultant 525 nm laser was 263 and 373 mW for the single and double resonant cavity, respectively. The corresponding quantum conversion efficiencies were 8 and 77\% for converting 1556 nm photons to 525 nm photons with the single and double r…

适用于混合量子光子学的超亮、高可扩展性压缩光源

An ultra-bright, highly-scalable, squeezed light source for hybrid quantum photonics

本文开发了适配混合量子光子学的超亮高可扩展KTP波导压缩光源，其具备高光子数、模式特性优异等优势，还建立了光子计数表征该光源的理论框架。