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arXiv:1406.3590 · Physical Review A

Time-multiplexed measurements of nonclassical light at telecom wavelengths

Georg Harder, Christine Silberhorn, Jaroslav Řeháček, Z. Hradil, L. Motka, B. Stoklasa, Luis Lorenzo Sánchez-Soto

Published Oct 7, 2014• 25 citations
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Abstract

We report the experimental reconstruction of the statistical properties of an ultrafast pulsed type II parametric down-conversion source in a periodically poled potassium titanyl phosphate waveguide at telecom wavelengths, with almost perfect photon-number correlations. We use a photon-number-resolving time-multiplexed detector based on a fiber-optical setup and a pair of avalanche photodiodes. By resorting to a germane data-pattern tomography, we assess the properties of the nonclassical light states with unprecedented precision.

DOI
10.1103/physreva.90.042105

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We report the experimental reconstruction of the statistical properties of an ultrafast pulsed type II parametric down-conversion source in a periodically poled potassium titanyl phosphate waveguide at telecom wavelengths, with almost perfect photon-number correlations. We use a photon-number-resolving time-multiplexed detector based on a fiber-optical setup and a pair of avalanche photodiodes. By resorting to a germane data-pattern tomography, we assess the properties of the nonclassical light states with unprecedented precision.
We report the experimental point-by-point sampling of the Wigner function for nonclassical states created in an ultrafast pulsed type-II parametric down-conversion source. We use a loss-tolerant time-multiplexed detector based on a fiber-optical setup and a pair of photon-number-resolving avalanche photodiodes. By capitalizing on an expedient data-pattern tomography, we assess the properties of the light states with outstanding accuracy. The method allows us to reliably infer the squeezing of genuine two-mode states without any phase reference.
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 spectral purity of 0.91 and coupling efficiencies around 90% for all four photons without any filtering. These pure indistinguishable photon sources at telecom wavelengths are perfectly adapted for quantum network demonstrations and other multi-photon protocols.
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 spectral purity of 0.91 and coupling efficiencies around 90% for all four photons without any filtering. These pure indistinguishable photon sources at telecom wavelengths are perfectly adapted for quantum network demonstrations and other multi-photon protocols.
Time-frequency domain is a promising platform for optical quantum technologies due to large Hilbert space available for quantum information encoding. Moreover, photons appear as perfect candidates for interface between different quantum systems as they can be transmitted over large distances in a low-loss manner. Obviously mostly desired would be such link at telecommunication wavelengths, because it can be integrated with classical communication schemes. We report on a tunable telecom-wavelength photon pair source based on bulk periodically poled potassium titanyl phosphate (PPKTP) pumped by femtosecond laser pulses. The pairs are produced via type-II spontaneous parametric down conversion (SPDC). The spectra of photons, which lies in telecommunication range, in our source can be affected via both changing the spectrum of pumping laser and changing the phase matching by using crystals of different lengths. By appropriate choice of these parameters either the pair of photons occupy single-mode in frequency and is in a separable state or is multimode and entangled [1]. Here we report on experimental active modification the photon pairs’ spectral properties. We employ fast electro-optic temporal phase modulation to induce a deterministic change of photons’ joint spectral intensity (JSI). Central wavelength of one photon is shifted by up to 0.2 nm. The measurement of the spectrum of single photons is based upon frequency to time mapping, implemented by large group delay dispersion (GDD) in chirped fiber Bragg grating (CFBG) [2]. An unprecedented sub-10 pm resolution of correlated single-photon spectral measurements has been achieved. Further work will be done to modify not only the position, but also the shape of JSI by using techniques based on the time-lens principle [3]. References: [1] P. G. Evans, R. S. Bennink, W. P. Grice, T. S. Humble, Phys. Rev. Lett. 105, 253601 (2010) [2] A. O. C. Davis, P. M. Saulnier, M. Karpinski, B. J. Smith, arXiv:1610.03040 (2016) [3] M. Karpiński, M. Jachura, L. J. Wright, B. J. Smith, Nature Photonics 11, 53–57 (2017)
We report on the generation of a bright photon source at telecom wavelengths using spontaneous parametric down-conversion in a type II periodically poled potassium titanyl phosphate crystal. Simultaneous resonances of the pump and the two down-converted fields are achieved with a properly designed optical cavity. This triple-resonance optical parametric oscillator operates far below threshold, generating photon pairs at 1560 nm wavelength with a bandwidth of 8 MHz. Time correlation measurements produce an estimate of 27.7 ns for the coherence time, and production rate of 134±25 s−1 MHz−1 mW−1 for photon pairs. As photon pairs in the telecom regime are suitable for long-distance transmission, this source may find application in quantum communications.
We demonstrate a scheme for femtosecond pulsed spontaneous parametric down-conversion in periodically poled potassium titanyl phosphate crystals. Our scheme is based on a crossed crystal configuration with collinear quasi-phase-matching. The nondegenerate photon pairs are split in a fiber-based wavelength division multiplexer. The source is easier to align than common pulsed sources based on bulk beta barium borate crystals and exhibits high-quality polarization entanglement as well as nonclassical interference capabilities. Hence, we expect this source to be a well-suited candidate for multiphoton state generation, e.g., for linear optical quantum computation and quantum communication networks.