对称二维简谐势阱中快速旋转的玻色-爱因斯坦凝聚体可以用单粒子朗道最低能级描述。凝聚波函数psi（x，y）是高斯exp（-r^2/2）乘以复变量z= x+ i y的解析函数f（z）。量子相变到非超流关联多体态的判据通常用粒子数与涡旋数的比值来表示。这里，类似的描述适用于具有任意二次各向异性（ω_x^2 <ω_y^2）的快速旋转的非对称二维陷阱。相应的凝聚体波函数psi（x，y）是一个复各向异性高斯函数，其相位正比于xy，乘以一个解析函数f（z），其中z = x + i β- y是一个拉伸的复变量，0< β- <1是一个实参数，它取决于陷阱的各向异性和旋转频率。无论是在平均场的高斯-费米近似，在平均场的最低朗道能级近似与许多可见的涡旋，各向异性的抛物线密度分布最小化的能量。伸长的冷凝物沿着软阱方向生长，但最终沿着紧阱方向收缩。量子相变到关联态的判据被推广为：（1）用N/L_z表示，这表明非对称陷阱应该使这种相变更容易观察;（2）用“碎片化”关联态表示，这表明非对称陷阱应该使这种相变更难观察。另一种方案涉及到一个准一维凝聚没有可见的旋涡交叉，如阿夫塔利翁等建议，Phys. Rev. A 79，011603（R）（2009）。
英文摘要：
A rapidly rotating Bose-Einstein condensate in a symmetric two-dimensional harmonic trap can be described with the lowest Landau-level set of single-particle states. The condensate wave function psi(x,y) is a Gaussian exp(-r^2/2), multiplied by an analytic function f(z) of the complex variable z= x+ i y. The criterion for a quantum phase transition to a non-superfluid correlated many-body state is usually expressed in terms of the ratio of the number of particles to the number of vortices. Here, a similar description applies to a rapidly rotating non-symmetric two-dimensional trap with arbitrary quadratic anisotropy (omega_x^2 < omega_y^2). The corresponding condensate wave function psi(x,y) is a complex anisotropic Gaussian with a phase proportional to xy, multiplied by an analytic function f(z), where z = x + i β_- y is a stretched complex variable and 0< β_- <1 is a real parameter that depends on the trap anisotropy and the rotation frequency. Both in the mean-field Thomas-Fermi approximation and in the mean-field lowest Landau level approximation with many visible vortices, an anisotropic parabolic density profile minimizes the energy. An elongated condensate grows along the soft trap direction yet ultimately shrinks along the tight trap direction. The criterion for the quantum phase transition to a correlated state is generalized (1) in terms of N/L_z, which suggests that a non-symmetric trap should make it easier to observe this transition or (2) in terms of a "fragmented" correlated state, which suggests that a non-symmetric trap should make it harder to observe this transition. An alternative scenario involves a crossover to a quasi one-dimensional condensate without visible vortices, as suggested by Aftalion et al., Phys. Rev. A 79, 011603(R) (2009).
Bose polarons as relativistic Unruh-DeWitt detectors: Entanglement harvesting from Bose-Einstein condensates
Nordita, KTH Royal Institute of Technology and Stockholm University（诺尔迪塔，皇家理工学院和斯德哥尔摩大学）；Kirchhoff-Institut für Physik, Universität Heidelberg（基希霍夫物理研究所，海德堡大学）
