Nearly degenerate wavelength-multiplexed polarization entanglement by cascaded optical nonlinearities in a PPLN ridge waveguide device

Abstract

In this paper we report the generation of wavelength-multiplexed polarization-entangled photon pairs in the 1.5-μm communication wavelength band by using cascaded optical second nonlinearities (sum-frequency generation and subsequent spontaneous parametric down-conversion, c-SFG/SPDC) in a periodically poled LiNbO(3) ridge waveguide device. The c-SFG/SPDC method makes it possible to fully use the broad spectral bandwidth of SPDC in nearly frequency-degenerate conditions, and can provide more than 50 pairs of wavelength channels for the entangled photon pairs in the 1.5-μm wavelength band, using only standard optical resources in the telecom field. Visibilities higher than 98% were clearly observed in two-photon interference fringes for all the wavelength channels under investigation (eight pairs). We further performed a detailed experimental investigation of the cross-talk characteristics and the impact of detuning the pump wavelengths.

Correlated photon pair generation in AlGaAs nanowaveguides via spontaneous four-wave mixing

“…Additionally, SFWM could create simultaneous, independent photon pairs into different wavelength channels over a broad spectral range given a fixed pump photon wavelength. This feature is very attractive in quantum channel multiplexing of the future quantum network [11,12].…”

Multi-user distribution of polarization entangled photon pairs

“…In order to evaluate the quality of the distributed entanglement and assess the effect of the various demultiplexers, we measure the following parameters: the visibility in the natural and the diagonal bases, V = (C max − C min )/(C max + C min ), where C max and C min are respectively the maximum and minimum number of coincidences when one of the polarisation basis angles is changed; the violation of the CHSH inequality, which is quantified by the Bell parameter S; and the brightness (21,27) 0.82 ± 0.04 0.77 ± 0.04 2.25 ± 0.07 216 0.20 0.970 ± 0.053 AWG (23,25) 0.77 ± 0.04 0.74 ± 0.05 2.10 ± 0.10 149 0.064 0.972 ± 0.059 AWG (22,26) 0.79 ± 0.05 0.66 ± 0.05 2.00 ± 0.10 116 0.079 0.906 ± 0.066 DGFT (23,25) 0.79 ± 0.05 0.82 ± 0.05 2.30 ± 0.10 108 0.030 1.000 ± 0.072 DGFT (22,26) 0 B. The results of our measurements are given in Table I.…”

“…In this case, the broad bandwidth of photon a) Electronic mail: isabelle.zaquine@telecom-paristech.fr pairs produced by spontaneous parametric down conversion can allow for entanglement distribution to multiple user pairs from a single source using wavelength division multiplexing techniques. This possibility has been explored in several recent works [22][23][24][25][26] , while further work is in progress to integrate these devices 27 and to design flexible optical networks based on such sources 28 . In view of the wide use of wavelength division multiplexing in quantum networks for practical applications, it is essential to be able to properly test the employed demultiplexing technologies and quantify their effect to the quality of the distributed entanglement 29 .…”

Two polarization-entangled sources from the same semiconductor chip

“…Entanglement in the polarization degree of freedom has been the most widely utilized to implement entangled sources for experiments and applications that probe or exploit quantum effects. Photon pairs in polarization entangled sources need to be indistinguishable in every degree of freedom, except for polarization, which is challenging to achieve for states produced directly in waveguides [8,15,16]. For photon pairs generated in a type-II process, in which the down-converted photons are crosspolarized, the birefringence in the group velocities of the modes, where the photons propagate, will cause a temporal walk-off between the pair, allowing polarization to be inferred from the photon arrival time.…”