标题： 量子磁振子学中磁振子数态的解析 显示英文标题

标题： Resolving magnon number states in quantum magnonics

摘要： 固态系统的集体激发模式在电路量子电动力学、腔光力力学和量子磁振子学中起着核心作用。在后者中，铁磁体中集体激发模式的准粒子（称为磁振子）与量子比特相互作用，以提供访问磁振子学中量子现象所需的非线性。 未来量子磁振子系统的关键组成部分之一是对磁振子状态的探测能力。在这里，我们在一个毫米大小的铁磁体中，通过与超导量子比特相干耦合，观察到了单个磁振子。 具体而言，在强色散条件下，我们通过transmon量子比特的光谱测量，分辨出了混合系统中的磁振子数态。这使我们能够检测到铁磁体磁偶极矩的变化，相当于在超过$10^{19}$个自旋中翻转了一个自旋。 量子磁振子学的强色散区域开启了将超导量子比特编码到非经典磁振子态的可能性，这可能为超导量子处理器和光学光子之间提供一个相干接口。 显示英文摘要

摘要： Collective excitation modes in solid state systems play a central role in circuit quantum electrodynamics, cavity optomechanics, and quantum magnonics. In the latter, quanta of collective excitation modes in a ferromagnet, called magnons, interact with qubits to provide the nonlinearity necessary to access quantum phenomena in magnonics. A key ingredient for future quantum magnonics systems is the ability to probe magnon states. Here we observe individual magnons in a millimeter-sized ferromagnet coherently coupled to a superconducting qubit. Specifically, we resolve magnon number states in spectroscopic measurements of a transmon qubit with the hybrid system in the strong dispersive regime. This enables us to detect a change in the magnetic dipole of the ferromagnet equivalent to a single spin flipped among more than $10^{19}$ spins. The strong dispersive regime of quantum magnonics opens up the possibility of encoding superconducting qubits into non-classical magnon states, potentially providing a coherent interface between a superconducting quantum processor and optical photons.