Christensen M B, Vibel T, Hilliard A J, Kruk M B, Pawłowski K, Hryniuk D, Rzążewski K, Kristensen M A, Arlt J J
Center for Complex Quantum Systems, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark.
Center for Theoretical Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland.
Phys Rev Lett. 2021 Apr 16;126(15):153601. doi: 10.1103/PhysRevLett.126.153601.
Quantum systems are typically characterized by the inherent fluctuation of their physical observables. Despite this fundamental importance, the investigation of the fluctuations in interacting quantum systems at finite temperature continues to pose considerable theoretical and experimental challenges. Here we report the characterization of atom number fluctuations in weakly interacting Bose-Einstein condensates. Technical fluctuations are mitigated through a combination of nondestructive detection and active stabilization of the cooling sequence. We observe fluctuations reduced by 27% below the canonical expectation for a noninteracting gas, revealing the microcanonical nature of our system. The peak fluctuations have near linear scaling with atom number ΔN_{0,p}^{2}∝N^{1.134} in an experimentally accessible transition region outside the thermodynamic limit. Our experimental results thus set a benchmark for theoretical calculations under typical experimental conditions.
量子系统通常由其物理可观测量的固有涨落来表征。尽管这具有根本重要性，但在有限温度下对相互作用量子系统中的涨落进行研究，仍然面临着相当大的理论和实验挑战。在此，我们报告了弱相互作用玻色 - 爱因斯坦凝聚体中原子数涨落的表征。通过无损检测和冷却序列的主动稳定相结合，技术涨落得以减轻。我们观察到涨落比非相互作用气体的正则预期降低了27%，揭示了我们系统的微正则性质。在热力学极限之外的实验可及转变区域，峰值涨落与原子数具有近似线性标度关系ΔN_{0,p}^{2}∝N^{1.134}。因此，我们的实验结果为典型实验条件下的理论计算设定了一个基准。
