with independent entangled photon-pair sources and Experimental - PowerPoint PPT Presentation

Entanglement swapping over 100 km optical fiber with independent entangled photon-pair sources and Experimental demonstration of nonbilocality Yang-Fan Jiang University of Science and Technology of China QCrypt 2018

Outline ① A brief review on Entanglement swapping ② Entanglement swapping over 100 km optical fiber ③ Experimental demonstration of nonbilocality ④ Summary and outlook 3/16

A brief review on Entanglement swapping EPR-sources State of this system Four Bell states 1 ( 1 ( 1 (    H V V H )        H V V H ) H V V H ) 1234 2 1 2 1 2 12 1 2 1 2 2 3 2 3 2 2 23   ( H V V H ) 1 ( 1 (        H V V H ) H H V V ) 3 4 3 4 34 3 4 3 4 2 3 2 3 2 2 23 1 (           2 14 23 14 23           ) 14 23 14 23 . 4/16 Zukowski M et al., Phys. Rev. Lett. 1993, 71(26): 4287 – 4290; J.-W. Pan et al., Phys. Rev. Lett. 1998, 80(18): 3891 – 3894.

A brief review on Entanglement swapping Applications ① Physics foundations nonlocality , wave –particle duality, … ( A. Peres, 2000; C. Branciard et al., 2010 … ) ② Quantum networks Quantum repeater, Quantum relay, Quantum key distribution, … (H. J. Briegel et al., 1998; L. M. Duan et al., 2001; Q.- C. Sun et al., 2017 …) T. Yang et al., Phys.Rev.Lett., 2006 Requirements M. Halder et al., 2007 ① Independent quantum sources R. Kaltenbaek et al., 2009 B. Hensen et al., Nature, 2015 (1.3 km) ② Field test R. Valivarthi et al., Nat. Photon., 2016 (17 km) Q.-C. Sun et al., Nat. Photon., 2016 (25 km) … 5/16

Outline ① A brief review on Entanglement swapping ② Entanglement swapping over 100 km optical fiber ③ Experimental demonstration of nonbilocality ④ Summary and outlook 3/16

Schematic diagram 12.5 km Alice Innovation Ind. Park Prepares& distributes EPR pairs, Performs state analysis Charlie Software Park BSM Bob USTC Prepares& distributes EPR pairs, Performs state analysis Transmission loss ： 29 dB Technical challenges: • 103 km of optical fiber Interference between independent photons (Indistinguishability of photons) Inside the lab ： 77 km; • Transmission loss outside the lab ： 25 km kept underground; 1 km suspended in air. • Stability of system and channel Map data: Google. CNES/Astrium. DigitalGlobe. 7/16

Sequential time-bin photon pairs source  Repetition rate 1 GHz  Pulse duration 75 ps  Extinction ratio > 26dB  1 n 1    ik = e t t k k s i n  k 0 Spontaneous four-wave-mixing in dispersion shifted fibre: Frequency correlation:    d       ( ) 2 2 p    ( ) 4 GHz s i   7 GHz p V  99% . Zhou et al. Phys. Lett. A 375 2274 (2011); Zukowski et al. Ann. N. Y. Acad. Sci, 755 91-102 (1995); 8/16 Q. Zhang et al. Opt. Express 16, 3293 – 329 8 (2008).

Sequential time-bin photon pairs source  1 n 1  The visibility of the fitted curve:   MZI ik = e t t k k s i n  k 0 (a) Alice: (89.8 ± 0.5)% 1         i n [( 1)2 ] (b) Bob: (82.9 ± 1.2)% = { t t e t t s i 0 0 n n s i s i 2 n  n 1           ik 2 i k [( 1)2 ] ([ e e ] t t ) s i  Multi pair events and the noise (~93%) k k s i  k 1  Temperature fluctuation (~96%)   n 1 n 1           i k ( 2 ) i k ( 2 ) e t t e t t } s i   k 1 k k k 1 s i s i  Limited bandwidth of the photodiode.   k 0 k 0        R 1 V cos( ) c s i 9/16 Q. Zhang et al. Opt. Express 16, 3293 – 3298 (2008).

Synchronization of independent sources RMS time jitter Which are much smaller than the coherent time of the signal photons ( ∼ 110 ps). 10/16

System stabilization Measure the difference between the arrival time of the signal photons Automatic stabilizations: • from Alice and Bob as error signals and feed them into delay lines. Time delay • Polarization • Measured by a TDC with time resolution of 4 ps • MZI, FBG, EOM, Pump power • Feedback interval time: 100 s ... 11/16

System stabilization The standard deviations of the relative delay: (a) : Rainy 6.7 ps , (b) : Cloudy 6.0 ps , (c) : Sunny 6.5 ps . Which are much smaller than the coherent time of the signal photons ( ∼ 110 ps). Our system can work well in different weather conditions. 12/16

Experimental results BSM: 1    = ( t t t t )   k k 1 k 1 k k 2 Created entanglement state: 1    = ( t t t t )   k k 1 k 1 k k 2 • Each data point is accumulated for more than 30 h • The average visibility is (73.2 ± 5.6)% Classical limit 1/3 13/16

Outline ① A brief review on Entanglement swapping ② Entanglement swapping over 100 km optical fiber ③ Experimental demonstration of nonbilocality ④ Summary and outlook 3/16

Experimental demonstration of nonbilocality Models where independent systems are characterized by different, uncorrelated hidden states λ .  V 50% biloc 1   V 70.7% CHSH 2 C. Branciard, N. Gisin,and S. Pironio, PRL 104, 170401 (2010)

Experimental demonstration of nonbilocality • True Independent source p: the noise parameter • Strict locality constraint Result: • Measurement independence B    1.181 0.004 1   S =2.652 0.059 2 CHSH arXiv: 1807.05375 This work is subject to press embargo!

Outline ① A brief review on Entanglement swapping ② Entanglement swapping over 100 km optical fiber ③ Experimental demonstration of nonbilocality ④ Summary and outlook 3/16

Summary and outlook The first experiment Our experiment has shown that realizing entanglement swapping between two  cities is technically feasible: The Second experiment  Our experimental realization constitutes a fundamental block for a large quantum network. • True Independent source • Strict locality constraint • Measurement independence Outlook ： • Test the fundamental issues of quantum information science • Stimulate novel information processing applications • Quantum networks with multi-sources, free-space channel, etc. 15/16

Acknowledgement USTC Qi-Chao Sun, Ya-Li Mao, Bing Bai, Xiao Jiang, Teng-Yun Chen, Jing-Yun Fan,Qiang Zhang, Jian-Wei Pan SIMIT Li-Xing You, Wei-Jun Zhang, Hao Li, Zhen Wang SJTU Xian-Feng Chen THU Wei Zhang, Yi-Dong Huang 2/16

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