Fig. 1. The Husimi distribution of spin coherent state (left) and spin squeezed state (right) on the generalized Bloch sphere. Adapted from Ref. [39]. 自旋相干态(左)与自旋压缩态(右)在广义Bloch球上的Husimi分布(摘自文献^[39])

Fig. 2. Top: The Husimi distribution of different spin cat states on the generalized Bloch sphere. Bottom: The ultimate phase measurement precision with different spin cat states under atomic loss ( denotes the ratio of atom loss). Adapted from Ref. [55]. 上图为不同自旋猫态在广义Bloch球上的Husimi分布; 下图为不同自旋猫态在有原子数损失( 为原子的损失率)情况下的相位测量精度极限(摘自文献[55])

Fig. 3. Schematic of precision phase measurement based on driving through quantum phase transitions and many-body quantum interferometry. Adapted from Ref. [61]. 基于量子相变和多体量子干涉的相位测量方案示意图( 摘自文献[61])

Fig. 4. (a) The thick black solid line denotes the gap between the first excited and the ground state of Hamiltonian, which together with the two minima at q = ±2|c₂| defines three quantum phases, illustrated by their atom distributions in the three spin components, the first-order Zeeman shifts are not shown because they are inconsequential for a system with zero magnetization; (b) absorption images of atoms in the three spin components after Stern-Gerlach separation, showing efficient conversion of a condensate from a polar state into a TFS by sweeping q linearly from 3|c₂| to –3| c₂| in 3 s. Adapted from Ref. [35]. (a)旋量BEC的基态由单原子内态的二阶塞曼效应和BEC中自旋交换作用强度的大小决定, 会出现两个相变点, 将相图分为三个区域, 分别为P, BA和TF相; (b)线性扫描q时, 通过吸收成像观察到的BEC在各个内态上的分布随时间的变化(摘自文献[35])