2021/01/31 by Hiroo Azuma, Masashi Ban · 1 citation
Computer Science · Mathematics · Physics and Astronomy · #Bound state #Coherent states #Cold Atom Physics and Bose-Einstein Condensates #Dephasing #Mathematical analysis #Mathematical physics #Mathematics #Physics #Quantum #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum mechanics #State (computer science) #Upper and lower bounds #Zero (linguistics) #quant-ph
paper · pdf · doi:10.1140/epjd/s10053-021-00180-x
published in The European Physical Journal D 75(6) (Springer Science+Business Media) · 29 pages, 14 eps figures, latex2e; v2: The title has been changed. We have improved Sect. 8 and added many references; v3: Equation (57) has been modified
openalex publication_date 2021/06/01 · arxiv created 2021/07/11 · arxiv updated 2021/07/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We show that in some cases the coherent state can have a larger violation of the Leggett-Garg inequality (LGI) than the cat state by numerical calculations. To achieve this result, we consider the LGI of the cavity mode weakly coupled to a zero-temperature environment as a practical instance of the physical system. We assume that the bosonic mode undergoes dissipation because of an interaction with the environment but is not affected by dephasing. Solving the master equation exactly, we derive an explicit form of the violation of the inequality for both systems prepared initially in the coherent state |α⟩ and the cat state (|α⟩+|-α⟩). For the evaluation of the inequality, we choose the displaced parity operators characterized by a complex number β. We look for the optimum parameter β that lets the upper bound of the inequality be maximum numerically. Contrary to our expectations, the coherent state occasionally exhibits quantum quality more strongly than the cat state for the upper bound of the violation of the LGI in a specific range of three equally spaced measurement times (spacing τ). Moreover, as we let τ approach zero, the optimized parameter β diverges and the LGI reveals intense singularity.