Bright-light detector control emulates the local bounds of Bell-type inequalities

Shihan Sajeed; Nigar Sultana; Charles Ci Wen Lim; Vadim Makarov

doi:10.1038/s41598-020-70045-7

Bright-light detector control emulates the local bounds of Bell-type inequalities

Sci Rep. 2020 Aug 6;10(1):13205. doi: 10.1038/s41598-020-70045-7.

Authors

Shihan Sajeed^{1

2

3

4}, Nigar Sultana^{5

6}, Charles Ci Wen Lim^{7

8}, Vadim Makarov^{9

10

11}

Affiliations

¹ Institute for Quantum Computing, University of Waterloo, Waterloo, ON, N2L 3G1, Canada. shihan.sajeed@gmail.com.
² Department of Physics and Astronomy, University of Waterloo, Waterloo, ON, N2L 3G1, Canada. shihan.sajeed@gmail.com.
³ Department of Electrical and Computer Engineering, University of Waterloo, N2L 3G1, Waterloo, ON, Canada. shihan.sajeed@gmail.com.
⁴ Department of Electrical and Computer Engineering, University of Toronto, M5S~3G4, Toronto, ON, Canada. shihan.sajeed@gmail.com.
⁵ Institute for Quantum Computing, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
⁶ Department of Electrical and Computer Engineering, University of Waterloo, N2L 3G1, Waterloo, ON, Canada.
⁷ Centre for Quantum Technologies, National University of Singapore, Singapore, Singapore.
⁸ Department of Electrical & Computer Engineering, National University of Singapore, Singapore, Singapore.
⁹ Russian Quantum Center, Skolkovo, Moscow, 121205, Russia.
¹⁰ Shanghai Branch, National Laboratory for Physical Sciences at Microscale and CAS Center for Excellence in Quantum Information, University of Science and Technology of China, Shanghai, 201315, People's Republic of China.
¹¹ NTI Center for Quantum Communications, National University of Science and Technology MISiS, Moscow, 119049, Russia.

Abstract

It is well-known that no local model-in theory-can simulate the outcome statistics of a Bell-type experiment as long as the detection efficiency is higher than a threshold value. For the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality this theoretical threshold value is [Formula: see text]. On the other hand, Phys. Rev. Lett. 107, 170404 (2011) outlined an explicit practical model that can fake the CHSH inequality for a detection efficiency of up to 0.5. In this work, we close this gap. More specifically, we propose a method to emulate a Bell inequality at the threshold detection efficiency using existing optical detector control techniques. For a Clauser-Horne-Shimony-Holt inequality, it emulates the CHSH violation predicted by quantum mechanics up to [Formula: see text]. For the Garg-Mermin inequality-re-calibrated by incorporating non-detection events-our method emulates its exact local bound at any efficiency above the threshold. This confirms that attacks on secure quantum communication protocols based on Bell violation is a real threat if the detection efficiency loophole is not closed.