2008/08/31 by Antonio Acín, Nicolas J. Cerf, Alessandro Ferraro +1 · 2 citations
Computer Science · Mathematics · Physics and Astronomy · #Bell test experiments #Bell's theorem #Cold Atom Physics and Bose-Einstein Condensates #Direct-conversion receiver #Homodyne detection #Mathematics #Multi-mode optical fiber #Multipartite #Optical fiber #Optics #Physics #Quantum #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum entanglement #Quantum mechanics #Quantum nonlocality #Quantum state #Robustness (evolution) #Statistical physics #Superposition principle #quant-ph
paper · pdf · doi:10.1103/physreva.79.012112
published as Phys. Rev. A 79, 012112 (2009) · 9 pages, 5 figures
arxiv created 2008/09/02 · openalex publication_date 2009/01/23 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We investigate the violation of local realism in Bell tests involving homodyne measurements performed on multimode continuous-variable states. By binning the measurement outcomes in an appropriate way, we prove that the Mermin-Klyshko inequality can be violated by an amount that grows exponentially with the number of modes. Furthermore, the maximum violation allowed by quantum mechanics can be attained for any number of modes, albeit requiring a quantum state whose generation is hardly practicable. Interestingly, this exponential increase of the violation holds true even for simpler states, such as multipartite GHZ states. The resulting benefit of using more modes is shown to be significant in practical multipartite Bell tests by analyzing the increase of the robustness to noise with the number of modes. In view of the high efficiency achievable with homodyne detection, our results thus open a possible way to feasible loophole-free Bell tests that are robust to experimental imperfections. We provide an explicit example of a three-mode state (a superposition of coherent states) which results in a significantly high violation of the Mermin-Klyshko inequality (around 10%) with homodyne measurements.