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Intensity correlations between neighbouring pulses open a prevalent yet often overlooked security loophole in decoy-state quantum key distribution (QKD). As a solution, we present and experimentally demonstrate an intensity-correlation-tolerant QKD protocol that mitigates the negative effect that this phenomenon has on the secret key rate according to existing security analyses. Compared to previous approaches, our method significantly enhances the robustness against correlations, notably improving both the maximum transmission distances and the achievable secret key rates across different scenarios. By relaxing constraints on correlation parameters, our protocol enables practical devices to counter intensity correlations. We experimentally demonstrate this first practical solution that directly overcomes this security vulnerability, establish the feasibility and efficacy of our proposal, taking a major step towards loophole-free and high-performance QKD.
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1 University of Science and Technology of China, Laboratory of Quantum Information, Hefei, China (GRID:grid.59053.3a) (ISNI:0000 0001 2167 9639); University of Science and Technology of China, Anhui Province Key Laboratory of Quantum Network, Hefei, China (GRID:grid.59053.3a) (ISNI:0000 0001 2167 9639); University of Science and Technology of China, CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei, China (GRID:grid.59053.3a) (ISNI:0000000121679639)
2 University of Science and Technology of China, Laboratory of Quantum Information, Hefei, China (GRID:grid.59053.3a) (ISNI:0000 0001 2167 9639); University of Science and Technology of China, Anhui Province Key Laboratory of Quantum Network, Hefei, China (GRID:grid.59053.3a) (ISNI:0000 0001 2167 9639); University of Science and Technology of China, CAS Center for Excellence in Quantum Information and Quantum Physics, Hefei, China (GRID:grid.59053.3a) (ISNI:0000000121679639); University of Science and Technology of China, Hefei National Laboratory, Hefei, China (GRID:grid.59053.3a) (ISNI:0000 0001 2167 9639)
3 University of Vigo, Vigo Quantum Communication Center, Vigo, Spain (GRID:grid.6312.6) (ISNI:0000 0001 2097 6738); University of Vigo, Escuela de Ingeniería de Telecomunicación, Department of Signal Theory and Communications, Vigo, Spain (GRID:grid.6312.6) (ISNI:0000 0001 2097 6738); University of Vigo, AtlanTTic Research Center, Vigo, Spain (GRID:grid.6312.6) (ISNI:0000 0001 2097 6738)