Ultra-high Q Acoustic Resonance in Superfluid 4He

超流光学力学：超流与超导凝聚体的耦合

Superfluid Optomechanics: Coupling of a Superfluid to a Superconducting Condensate

我们研究了超流$^4$ He的低损耗声学运动，参数耦合到一个非常低损耗的超导Nb，TE $_{011}$微波谐振器，形成一个克级，边带分辨，光机系统。我们证明了一系列的声学模式的检测与品质因数高达$7\cdot 10^6$。在较高的温度下，最低的耗散模式是由一个固有的三声子过程的限制。在低于10 mK的温度下，同位素纯化的样品中可能存在接近$10^{11}$的声学品质因数。这种类型的系统可用于研究宏观量化运动，并作为极弱位移和力的超灵敏传感器，例如连续重力波源。

Quantitative acoustic models for superfluid circuits

We experimentally realize a highly tunable superfluid oscillator circuit in a quantum gas of ultracold atoms and develop and verify a simple lumped-element description of this circuit. At low oscillator currents, we demonstrate that the circuit is accurately described as a Helmholtz resonator, a fundamental element of acoustic circuits. At larger currents, the breakdown of the Helmholtz regime is heralded by a turbulent shedding of vortices and density waves. Although a simple phase-slip model offers qualitative insights into the circuit's resistive behavior, our results indicate deviations fr…

Quantum simulation of discrete curved spacetime by the Bose-Hubbard model: from analog acoustic black hole to quantum phase transition

We present a theoretical scheme to simulate quantum field theory in a discrete curved spacetime based on the Bose-Hubbard model describing a Bose-Einstein condensate trapped inside an optical lattice. Using the Bose-Hubbard Hamiltonian, we first introduce a hydrodynamic presentation of the system evolution in discrete space. We then show that the phase (density) fluctuations of the trapped bosons inside an optical lattice in the superfluid (Mott insulator) state obey the Klein-Gordon equation for a massless scalar field propagating in a discrete curved spacetime. We derive the effective metric…

Theory of Optomechanical Interactions in Superfluid He

A general theory is presented to describe optomechanical interactions of acoustic phonons, having extremely long lifetimes in superfluid $^4$He, with optical photons in the medium placed in a suitable electromagnetic cavity. The acoustic nonlinearity in the fluid motion is included to consider processes beyond the usual linear process involving absorption or emission of one phonon at a time. We first apply our formulation to the simplest one-phonon process involving the usual resonant anti-Stokes upconversion of an incident optical mode. However, when the allowed optical cavity modes are such …

超流体线涡上声的传播：各能区的作用

Propagation of sound on line vortices is superfluids: role of ergoregions

利用声学时空理论，研究了超流体中存在钉扎无旋涡旋时小扰动（声波）的传播。给出了声线散射角的封闭公式，将声传播问题表述为哈密顿形式，并讨论了涡核处的边界条件形式，其中哈密顿具有奇点。将波动方程简化为一个Mathieu型常微分方程。我们给出了一个广泛的讨论本地化的核心，这是类似于所谓的开尔文波。模式的频谱强烈地依赖于靠近涡核的边界条件的类型。无隙开尔文模是角数为-1的模之一，它的存在通常在超流氦或旋转玻色-爱因斯坦凝聚体中的非钉扎涡旋中讨论。我们证明，这种特殊的模式是不存在的，如果涡被钉扎，因此，在这种情况下，必须讨论整个家庭的模式。声学时空是否存在能域的问题，对声音传播现象的许多方面都有决定性的（定性的）影响。

超冷原子超流体中Majorana费米子的非阿贝尔统计性质

Probing non-Abelian statistics of Majorana fermions in ultracold atomic superfluid

我们提出了一个实验，直接探测非阿贝尔统计的马约拉纳费米子编织它们在一个s波超流体的超冷原子。我们表明，不同的编织操作顺序给出正交输出状态，可以通过拉曼光谱进行区分。在s波超流体中实现Majorana束缚态需要强的自旋轨道耦合和垂直方向的可控塞曼场。我们提出了一个简单的激光配置来产生人工自旋轨道耦合和所需的塞曼场的暗态子空间。