High quality asynchronous heralded single photon source at telecom wavelength

We report on the experimental realization and characterization of an asynchronous heralded single photon source based on spontaneous parametric down conversion. Photons at 1550nm are heralded as being inside a single-mode fiber with more than 60% probability, and the multi-photon emission probability is reduced by up to a factor 600 compared to poissonian light sources. These figures of merit, together with the choice of telecom wavelength for the heralded photons are compatible with practical applications needing very efficient and robust single photon sources.Comment: 7 pages, 8 figure

Silicon subwavelength modal Bragg grating filters with narrow bandwidth and high optical rejection

[EN] Waveguide Bragg grating filters with narrow bandwidths and high optical rejections are key functions for several advanced silicon photonics circuits. Here, we propose and demonstrate a new, to the best of our knowledge, Bragg grating geometry that provides a narrowband and high rejection response. It combines the advantages of subwavelength and modal engineering. As a proof-of-concept demonstration, we implement the proposed Bragg filters in 220-nm-thick Si technology with a single etch step. We experimentally show flexible control of the filter selectivity, with measured null-to-null bandwidths below 2 nm, and strength of 60 dB rejection with a null-to-null bandwidth of 1.8 nm.Agence Nationale de la Recherche (ANR-MIRSPEC-17-CE09-0041, ANR-SITQOM-15-CE24-0005); European Research Council (ERC POPSTAR 647342).Oser, D.; Pérez-Galacho, D.; Le Roux, X.; Tanzilli, S.; Vivien, L.; Labonte, L.; Cassan, E.... (2020). Silicon subwavelength modal Bragg grating filters with narrow bandwidth and high optical rejection. Optics Letters. 45(20):5784-5787. https://doi.org/10.1364/OL.394455S578457874520Azzini, S., Grassani, D., Strain, M. J., Sorel, M., Helt, L. G., Sipe, J. E., … Bajoni, D. (2012). Ultra-low power generation of twin photons in a compact silicon ring resonator. Optics Express, 20(21), 23100. doi:10.1364/oe.20.023100Jiang, W. C., Lu, X., Zhang, J., Painter, O., & Lin, Q. (2015). Silicon-chip source of bright photon pairs. Optics Express, 23(16), 20884. doi:10.1364/oe.23.020884Mazeas, F., Traetta, M., Bentivegna, M., Kaiser, F., Aktas, D., Zhang, W., … Tanzilli, S. (2016). High-quality photonic entanglement for wavelength-multiplexed quantum communication based on a silicon chip. Optics Express, 24(25), 28731. doi:10.1364/oe.24.028731Gisin, N., Ribordy, G., Tittel, W., & Zbinden, H. (2002). Quantum cryptography. Reviews of Modern Physics, 74(1), 145-195. doi:10.1103/revmodphys.74.145Knill, E., Laflamme, R., & Milburn, G. J. (2001). A scheme for efficient quantum computation with linear optics. Nature, 409(6816), 46-52. doi:10.1038/35051009Piekarek, M., Bonneau, D., Miki, S., Yamashita, T., Fujiwara, M., Sasaki, M., … Thompson, M. G. (2017). High-extinction ratio integrated photonic filters for silicon quantum photonics. Optics Letters, 42(4), 815. doi:10.1364/ol.42.000815Oser, D., Tanzilli, S., Mazeas, F., Alonso-Ramos, C., Le Roux, X., Sauder, G., … Labonté, L. (2020). High-quality photonic entanglement out of a stand-alone silicon chip. npj Quantum Information, 6(1). doi:10.1038/s41534-020-0263-7Pérez-Galacho, D., Alonso-Ramos, C., Mazeas, F., Le Roux, X., Oser, D., Zhang, W., … Vivien, L. (2017). Optical pump-rejection filter based on silicon sub-wavelength engineered photonic structures. Optics Letters, 42(8), 1468. doi:10.1364/ol.42.001468Klitis, C., Cantarella, G., Strain, M. J., & Sorel, M. (2017). High-extinction-ratio TE/TM selective Bragg grating filters on silicon-on-insulator. Optics Letters, 42(15), 3040. doi:10.1364/ol.42.003040Xia, F., Rooks, M., Sekaric, L., & Vlasov, Y. (2007). Ultra-compact high order ring resonator filters using submicron silicon photonic wires for on-chip optical interconnects. Optics Express, 15(19), 11934. doi:10.1364/oe.15.011934Dong, P., Feng, N.-N., Feng, D., Qian, W., Liang, H., Lee, D. C., … Asghari, M. (2010). GHz-bandwidth optical filters based on high-order silicon ring resonators. Optics Express, 18(23), 23784. doi:10.1364/oe.18.023784Ding, Y., Pu, M., Liu, L., Xu, J., Peucheret, C., Zhang, X., … Ou, H. (2011). Bandwidth and wavelength-tunable optical bandpass filter based on silicon microring-MZI structure. Optics Express, 19(7), 6462. doi:10.1364/oe.19.006462Horst, F., Green, W. M. J., Assefa, S., Shank, S. M., Vlasov, Y. A., & Offrein, B. J. (2013). Cascaded Mach-Zehnder wavelength filters in silicon photonics for low loss and flat pass-band WDM (de-)multiplexing. Optics Express, 21(10), 11652. doi:10.1364/oe.21.011652Wang, J., Glesk, I., & Chen, L. R. (2015). Subwavelength grating Bragg grating filters in silicon‐on‐insulator. Electronics Letters, 51(9), 712-714. doi:10.1049/el.2015.0546Zou, Z., Zhou, L., Wang, M., Wu, K., & Chen, J. (2016). Tunable spiral Bragg gratings in 60-nm-thick silicon-on-insulator strip waveguides. Optics Express, 24(12), 12831. doi:10.1364/oe.24.012831Cheben, P., Čtyroký, J., Schmid, J. H., Wang, S., Lapointe, J., Wangüemert-Pérez, J. G., … Dado, M. (2019). Bragg filter bandwidth engineering in subwavelength grating metamaterial waveguides. Optics Letters, 44(4), 1043. doi:10.1364/ol.44.001043Oser, D., Mazeas, F., Le Roux, X., Pérez‐Galacho, D., Alibart, O., Tanzilli, S., … Alonso‐Ramos, C. (2019). Coherency‐Broken Bragg Filters: Overcoming On‐Chip Rejection Limitations. 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A multiplexed synthesizer for non-Gaussian photonic quantum state generation

Disposing of simple and efficient sources for photonic states with non-classical photon statistics is of paramount importance for implementing quantum computation and communication protocols. In this work, we propose an innovative approach that drastically simplifies the preparation of non-Gaussian states as compared to previous proposals, by taking advantage from the multiplexing capabilities offered by modern quantum photonics tools. Our proposal is inspired by iterative protocols, where multiple resources are combined one after the other for obtaining high-amplitude complex output states. Here, conversely, a large part of the protocol is performed in parallel, by using a single projective measurement along a mode which partially overlaps with all the input modes. We show that our protocol can be used to generate high-quality and high-amplitude Schrödinger cat states as well as more complex states such as error-correcting codes. Remarkably, our proposal can be implemented with experimentally available resources, highlighting its straightforward feasibility

A multiplexed synthesizer for non-Gaussian photonic quantum state generation

Disposing of simple and efficient sources for photonic states with non-classical photon statistics is of paramount importance for implementing quantum computation and communication protocols. In this work, we propose an innovative approach that drastically simplifies the preparation of non-Gaussian states as compared to previous proposals, by taking advantage from the multiplexing capabilities offered by modern quantum photonics tools. Our proposal is inspired by iterative protocols, where multiple resources are combined one after the other for obtaining high-amplitude complex output states. Here, conversely, a large part of the protocol is performed in parallel, by using a single projective measurement along a mode which partially overlaps with all the input modes. We show that our protocol can be used to generate high-quality and high-amplitude Schrödinger cat states as well as more complex states such as error-correcting codes. Remarkably, our proposal can be implemented with experimentally available resources, highlighting its straightforward feasibility

Hidden and detectable squeezing from microresonators

In the context of quantum integrated photonics, this work investigates the quantum properties of multimode light generated by silicon and silicon nitride microresonators pumped in pulsed regime. The developed theoretical model provides a comprehensive description of the generated quantum states. Remarkably, it shows that a full measurement of states carrying optimal squeezing levels is not accessible to standard homodyne detection, thus leaving hidden part of generated quantum features. By unveiling and discussing this behavior and possible strategies to amend it, this work proves itself essential to future quantum applications exploiting microresonators as sources of multimode states

Segmented waveguide tapers for low insertion loss, high performance SPE:LiNbO_3 integrated circuits

We present the results of an experimental study of waveguide tapers realized with segmented waveguides in LiNbO_3 substrates using the Soft Proton Exchange (SPE) technique. Measurements show that the tapers can be favorably introduced between the nonlinear or electro-optic part of the components, which requires strong mode confinement to increase efficiency, and the coupling section with a standard optical fiber, which requires low mode confinement, in order to have low coupling losses. These tapers allow almost lossless mode shape transformation with a reduction of the coupling losses up to 0.7 dB, thus proving the practical interest of the approach. As an example, the use of such tapers in a real integrated optical circuit is shown

Insertion loss reduction of SPE:LiNb03 integrated circuits using segmented waveguide tapers

We present an experimental study of waveguide tapers realized with segmented waveguides in LiNbO_3 substrates using the Soft Proton Exchange technique. Measurements show that the tapers introduced between the nonlinear part of the components, which requires strong mode confinement to increase the efficiency, and a standard optical fiber, which requires low mode confinement, reduce the coupling losses up to 0.7 dB, thus proving the practical interest of the approach. The use of such tapers in a real integrated optical circuit is also shown

Bragg-scattering conversion at telecom wavelengths towards the photon counting regime

We experimentally study Bragg-scattering four-wave mixing in a highly nonlinear fiber at telecom wavelengths using photon counters. We explore the polarization dependence of this process with a continuous wave signal in the macroscopic and attenuated regime, with a wavelength shift of 23 nm. Our measurements of mean photon numbers per second under various pump polarization configurations agree well with the theoretical and numerical predictions based on classical models. We discuss the impact of noise under these different polarization configurations