Ultrabright Multiplexed Energy-Time-Entangled Photon Generation from Lithium Niobate on Insulator Chip

Guang-Tai Xue, Yun-Fei Niu, Xiaoyue Liu, Jia-Chen Duan, Wenjun Chen, Ying Pan, Kunpeng Jia, Xiaohan Wang, Hua-Ying Liu, Yong Zhang, Ping Xu, Gang Zhao, Xinlun Cai, Yan-Xiao Gong, Xiaopeng Hu, Zhenda Xie, and Shining Zhu

Phys. Rev. Applied 15, 064059 – Published 24 June 2021

Abstract

A high-flux entangled-photon source is a key resource for quantum optical study and application. Here, it is realized in a lithium niobate on isolator (LNOI) chip, with 2.79 × $10^{11}$ Hz/mW photon-pair rate and 1.53 × $10^{9}$ Hz/(nm mW) spectral brightness. These data are boosted by over 2 orders of magnitude compared with existing technologies. A 160-nm-broad bandwidth is engineered for eight-channel multiplexed energy-time entanglement. Harnessed by high-extinction-frequency correlation and Franson interferences up to 99.17% visibility, such energy-time-entanglement multiplexing further enhances the high-flux data rate and warrants broad application in quantum-information processing on a chip.

Received 23 March 2020
Revised 30 November 2020
Accepted 9 June 2021

DOI:https://doi.org/10.1103/PhysRevApplied.15.064059

Physics Subject Headings (PhySH)

Integrated optics Optical quantum information processing Optoelectronics Photon pairs & parametric down-conversion Quantum state engineering Second order nonlinear optical processes

Optical sources & detectors Waveguides

Quantum Information, Science & TechnologyAtomic, Molecular & Optical

Authors & Affiliations

Guang-Tai Xue ^1,§, Yun-Fei Niu^1,§, Xiaoyue Liu ^2,§, Jia-Chen Duan^1,§, Wenjun Chen², Ying Pan², Kunpeng Jia¹, Xiaohan Wang ¹, Hua-Ying Liu¹, Yong Zhang¹, Ping Xu^3,1, Gang Zhao¹, Xinlun Cai ², Yan-Xiao Gong ^1,*, Xiaopeng Hu^1,†, Zhenda Xie^1,‡, and Shining Zhu¹

¹National Laboratory of Solid State Microstructures, School of Physics, School of Electronic Science and Engineering, College of Engineering and Applied Sciences, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
²State Key Laboratory of Optoelectronic Materials and Technologies and School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China
³Institute for Quantum Information and State Key Laboratory of High Performance Computing, College of Computing, National University of Defense Technology, Changsha 410073, China

^*gongyanxiao@nju.edu.cn
^†xphu@nju.edu.cn
^‡xiezhenda@nju.edu.cn
^§These authors contributed equally to this work.

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Vol. 15, Iss. 6 — June 2021

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Images

Figure 1
Schematic of chip design and fabrication. (a) Cross section of waveguide and mode field simulation, with parameters w = 1.4 µm, h₁= 350 nm, h₂= 600 nm, and θ = 60°. (b) Simulation of GVD for LNOI waveguide (red line) and bulk lithium niobate crystal (blue line). (c) Quasi-phase-matching geometry, with p, s, and i denoting pump, signal, and idler fields, respectively. (d) Electrode structure and electrical field poling process. High-voltage pulses are applied along z axis of X-cut LNOI wafer. (e) Confocal laser scanning microscopy picture of domain structure. Black areas are domain walls and electrodes in poling region and outside. (f) Schematic of chip-fabrication process.
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Figure 2
Schematic of experimental setup, including following four parts: (a) energy-time-entangled photon-pair source based on PPLNOI chip, (b) tunable-wavelength division multiplexing filtering system, (c) coincidence count system, and (d) Franson interferometer to test energy-time entanglement. AM, aspheric lens; LP, long-pass filter; M, mirror; RM, rectangular mirror; DM, D-shaped mirror; PBS, polarizing beam splitter; BS, 50:50 fiber beam splitter; FRM, Faraday rotator mirror; PC, polarization controller; TEC, thermoelectric cooler; CWDM, commercial coarse-wavelength-division multiplexer; SNSPD, superconducting-nanowire single-photon detector; TCSPC, time-correlated single-photon counting. Letters O, A, B, C, D₁, D₂, F₁, and F₂ represent input or output ports of the four parts, which are separated and can be connected in different ways, as needed.
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Figure 3
Spectrum characterization of source. (a) SPDC spectrum. Black points represent coincidence counts as a function of filtering wavelength of one photon, with the other photon unfiltered. Error bars represent square roots of counts. Red solid curve is fitted with a sinc-chirped square function. (b) Frequency-correlation measurement. Coincidence counts are recorded against wavelengths of photons from couplers B and C in steps of 10 nm.
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Figure 4
Multiplexed energy-time-entanglement characterization. (a) Illustration of multiplexed energy-time-entanglement generation from our source. Franson interferences are measured for each wavelength bin after the WDM filter, with coincidence counting (C. C.) measurement. (b)–(i) Experimental results of coincidence counts for entangled photons in eight pairs of wavelength channels, α_j, β_j (j = 1, 2,…, 8), as a function of the phase difference of both photons taking the long arm and both taking the short arm, with error bars denoting square root of counts. All curves are fitted with sine-cosine functions, with corresponding visibilities listed on top, where errors are estimated assuming Poisson fluctuation in counts.
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Figure 5
Simulation of source spectrum based on theoretical design.
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