Third-order Spontaneous Parametric Down-conversion Research Articles

Engineering the spectra of photon triplets generated from micro/nanofiber

Quantum light sources are the core resources for photonics-based quantum information processing. We investigate the spectral engineering of photon triplets generated by third-order spontaneous parametric down-conversion in micro/nanofiber. The phase mismatching at one–third pump frequency gives rise to non-degenerate photon triplets, the joint spectral intensity of which has an elliptical locus with a fixed eccentricity of 6/3 . Therefore, we propose a frequency-division scheme to separate non-degenerate photon triplets into three channels with high heralding efficiency for the first time. Choosing an appropriate pump wavelength can compensate for the fabrication errors of micro/nanofiber and also generate narrowband, non-degenerate photon triplet sources with a high signal-to-noise ratio. Furthermore, the long-period micro/nanofiber grating introduces a new controllable degree of freedom to tailor phase matching, resulting from the periodic oscillation of dispersion. In this scheme, the wavelength of photon triplets can be flexibly tuned using quasi-phase matching. We study the generation of photon triplets from this novel perspective of spectrum engineering, and we believe that this work will accelerate the practical implementation of photon triplets in quantum information processing.

Influence of pump brightness, self-Kerr and cross-Kerr effects on the entanglement of partially degenerate triple-photon state

Recently, partially degenerate triple-photon states (TPS) generated by the third-order spontaneous parametric down-conversion have been observed in a superconducting cavity (2020, Phys. Rev. X 10, 011011). Their non-Gaussian entanglement properties, characterized by a series of high-order covariance matrices, have also been theoretically revealed. Here, we use the non-Gaussian entanglement criterion proposed in (2021, Phy. Rev. Lett. 127, 150502) and the logarithmic negativity to study the effect of pump brightness, self-Kerr and cross-Kerr interactions on the entanglement of partially degenerate TPS (PDTPS). We find that the brighter the pump, the easier the entanglement of PDTPS leap to higher-order covariance matrices. Although both self-Kerr and cross-Kerr interactions induce nonlinear phase shifts and weaken the entanglement of PDTPS, cross-Kerr interactions can effectively raise the threshold of entanglement loaded on the third-order covariance matrix. These results can contribute to our understanding of the mechanism of the generation of unconditional non-Gaussian entanglement.

Quantifying tripartite entanglement with entropic correlations

The authors develop techniques to quantify multipartite and high-dimensional entanglement using information-based measures of correlation and uncertainty, and show the large amounts of multi-partite entanglement available in photon triplets generated in third-order Spontaneous Parametric Down-Conversion

Luminescence in germania-silica fibers in a 1-2μm region.

We analyze the origins of the luminescence in germania-silica fibers with high germanium concentration (about 30mol.% GeO2) in the region of 1-2μm with a laser pump at the wavelength 532nm. We show that such fibers demonstrate the high level of luminescence which unlikely allows the observation of photon triplets, generated in a third-order spontaneous parametric downconversion process in such fibers. The only efficient approach to the luminescence reduction is the hydrogen saturation of fiber samples; however, even in this case, the level of residual luminescence is still too high for three-photon registration.

Third-order spontaneous parametric down-conversion in a ring microcavity

The theory of third-order spontaneous parametric down-conversion (TOSPDC) in a ring waveguide microcavity is developed. Analytical expressions for the rate of photon triplet emission are presented for both the monochromatic-pump and pulsed-pump regimes. In the latter case, rising exponential pulses are considered as optimal ones for the cavity excitation. It is demonstrated by numerical simulations that a silicon-nitride based ring microcavity can be a promising system for developing narrowband sources of photon triplets based on TOSPDC.

Efficient photon triplet generation in integrated nanophotonic waveguides.

Generation of entangled photons in nonlinear media constitutes a basic building block of modern photonic quantum technology. Current optical materials are severely limited in their ability to produce three or more entangled photons in a single event due to weak nonlinearities and challenges achieving phase-matching. We use integrated nanophotonics to enhance nonlinear interactions and develop protocols to design multimode waveguides that enable sustained phase-matching for third-order spontaneous parametric down-conversion (TOSPDC). We predict a generation efficiency of 0.13 triplets/s/mW of pump power in TiO2-based integrated waveguides, an order of magnitude higher than previous theoretical and experimental demonstrations. We experimentally verify our device design methods in TiO2 waveguides using third-harmonic generation (THG), the reverse process of TOSPDC that is subject to the same phase-matching constraints. We finally discuss the effect of finite detector bandwidth and photon losses on the energy-time coherence properties of the expected TOSPDC source.

Three-photon generation by means of third-order spontaneous parametric down-conversion in bulk crystals

We investigate the third-order spontaneous parametric down-conversion process in a nonlinear media with inversion centers. Specifically, we analyze in details the three-photon differential count rate in unit frequency and angular regions, total count rate and measurement time for rutile and calcite crystals which have comparatively large cubic susceptibilities. Special attention is given to consideration of limited frequency and angular detection ranges in order to calculate experimentally available detection rate values.

Third-order spontaneous parametric down-conversion in thin optical fibers as a photon-triplet source

We study the third order spontaneous parametric down conversion (TOSPDC) process, as a means to generate entangled photon triplets. Specifically, we consider thin optical fibers as the nonlinear medium to be used as the basis for TOSPDC in configurations where phase matching is attained through the use of more than one fiber transverse modes. Our analysis in this paper, which follows from our earlier paper Optics Letters 36, 190 (2011), aims to supply experimentalists with the details required in order to design a TOSPDC photon-triplet source. Specifically, our analysis focuses on the photon triplet state, on the rate of emission, and on the TOSPDC phasematching characteristics for the cases of frequency degenerate and frequency nondegenerate TOSPDC.

Experimental proposal for the generation of entangled photon triplets by third-order spontaneous parametric downconversion in optical fibers

We present an experimental proposal for the generation of photon triplets based on third-order spontaneous parametric downconversion in thin optical fibers. Our analysis includes expressions for the quantum state, which describes the photon triplets and for the generation rate in terms of all experimental parameters. We also present, for a specific source design, numerically calculated generation rates.