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arXiv:2210.12466 · Journal of the Optical Society of America B

Design of mid-infrared entangled photon sources using lithium niobate

Jin-Long Zhu, Wen-Xin Zhu, Xiao-Tao Shi, Chen-Tao Zhang, Xiangying Hao, Zi-Xiang Yang, Rui‐Bo Jin

Published Sep 16, 2022• 11 citations
arXivHTMLPDF

Abstract

The mid-infrared (MIR) band entangled photon source is vital for the next generation of quantum communication, quantum imaging, and quantum sensing. However, the current entangled states are mainly prepared in the visible or near-infrared bands. It is still lacking high-quality entangled photon sources in the MIR band. In this work, we optimize the poling sequence of lithium niobate to prepare two kinds of typical entangled states, the Hermit–Gaussian state and the comb-like entangled state at 3.2 µm. We have also calculated the photon pair rates and estimated the effect of fabrication resolution in the schemes. Our approach will provide entangled photon sources with excellent performance for the study of quantum information in the MIR band.

DOI
10.1364/josab.469376

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The mid-infrared (MIR) band entangled photon source is vital for the next generation of quantum communication, quantum imaging, and quantum sensing. However, the current entangled states are mainly prepared in the visible or near-infrared bands. It is still lacking high-quality entangled photon sources in the MIR band. In this work, we optimize the poling sequence of lithium niobate to prepare two kinds of typical entangled states, the Hermit–Gaussian state and the comb-like entangled state at 3.2 µm. We have also calculated the photon pair rates and estimated the effect of fabrication resolution in the schemes. Our approach will provide entangled photon sources with excellent performance for the study of quantum information in the MIR band.
The single-photon source in mid-infrared (MIR) band is very important for the next generation of quantum sensing, quantum communication and quantum imaging. At present, the commonly used method of generating MIR single-photon source is based on the spontaneous parametric down conversion (SPDC) process in the periodically poled lithium niobate (PPLN) crystal. However, the spectral purity of single-photon source based on the ordinary PPLN is not high, specifically, its maximum value is only about 0.82, which affects the fidelity of quantum information processing scheme. In this paper, 4000 polarized domains in a 30-mm-long LN crystal are customized by using the domain design theory. The sidelobes in the phase matching function are eliminated, and the Gaussian distribution is obtained. The calculated spectral purity of the single-photon source can reach 0.99, and its tunable range is 2.7–3.3 μm. The customized poled lithium niobate (CPLN) is expected to provide a single-photon source with excellent performance for the study of quantum information in the MIR band.
Mid-infrared quantum light sources hold broad application prospects in fields such as gas sensing and infrared thermal imaging. However, currently used mid-infrared quantum entangled light sources primarily rely on bulk periodically poled lithium niobate (PPLN) crystals, which limits brightness and integration. This paper proposes a theoretical scheme based on lithium niobate thin films, in which 1556.9 nm pumping is used to generate entangled photon pairs with a central wavelength of 3113.8 nm. By optimizing the waveguide structure and periodic polarization design, type-II phase matching and group velocity matching are achieved. This enables transverse electric (TE)-polarized pump input to be down converted to generate photon pairs with TE and transverse magnetic (TM) polarizations. Furthermore, by combining a domain arrangement algorithm used for the customized design of polarization direction in PPLN waveguides, precise phase matching is achieved, resulting in a quantum light source with a purity as high as 0.999 and a brightness of 6.18×106\times 10^6×106 cps/mW, which is three orders of magnitude higher than that of the bulk PPLN crystal source. This study provides a promising solution for realizing high-brightness, high-purity on-chip quantum light sources in the mid-infrared band.
Quantum-enhanced optical technologies operating within the 2- to 2.5-μm spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. Currently, sources of entangled photons are available at visible, near-infrared and telecom wavelengths but are strongly underdeveloped at longer wavelengths. Here, using custom-designed lithium niobate crystals for spontaneous parametric down-conversion and tailored superconducting nanowire single-photon detectors, we demonstrate two-photon interference and polarization-entangled photon pairs at 2090 nm. These results open the 2- to 2.5-μm mid-infrared window for the development of optical quantum technologies such as quantum key distribution in next-generation mid-infrared fiber communication systems and future Earth-to-satellite communications.
Photon entanglement is essential for quantum communication, sensing, and computing. While research on frequency-degenerate entangled photons in the near-infrared (NIR) region has advanced significantly, entangled light spanning mid-infrared (MIR) and visible (VIS) frequencies remains under development [1]. For instance, in the MIR region, chiral collective lattice vibration modes that exhibit selectivity for circularly polarized light have been observed in two-dimensional layered materials [2], suggesting the existence of quantum entanglement with electronic states [3]. This entanglement could lead to the conservation of quantum states. For this purpose, it is necessary to generate quantum entangled states of photons in the MIR and VIS regions with high fidelity.
Quantum-enhanced optical systems operating within the 2- to 2.5-μm spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. However, to date, sources of entangled photons have been realized mainly in the near-infrared 700- to 1550-nm spectral window. Here, using custom-designed lithium niobate crystals for spontaneous parametric down-conversion and tailored superconducting nanowire single-photon detectors, we demonstrate two-photon interference and polarization-entangled photon pairs at 2090 nm. These results open the 2- to 2.5-μm mid-infrared window for the development of optical quantum technologies such as quantum key distribution in next-generation mid-infrared fiber communication systems and future Earth-to-satellite communications.