Detecting a single magnetic excitation Quantum-enhanced sensing is one of the near-term applications for the developing field of quantum technologies. A promising approach to quantum sensing relies on entangling a well-controlled system (the sensor) to the system of interest to detect quanta of excitations in the latter. By entangling a superconducting qubit with a ferrimagnetic crystal, Lachance-Quirion et al. demonstrate that they can detect a quantum of magnetic excitation (a magnon) within the sample. The demonstration of a high-efficiency single-magnon detector will be useful for quantum sensing as well as an active component of hybrid quantum systems and should find a wide range of applications in quantum technologies. Science, this issue p. 425 A superconducting qubit can detect a single magnon in a magnetic crystal via quantum entanglement. The recent development of hybrid systems based on superconducting circuits provides the possibility of engineering quantum sensors that exploit different degrees of freedom. Quantum magnonics, which aims to control and read out quanta of collective spin excitations in magnetically ordered systems, provides opportunities for advances in both the study of magnetism and the development of quantum technologies. Using a superconducting qubit as a quantum sensor, we report the detection of a single magnon in a millimeter-sized ferrimagnetic crystal with a quantum efficiency of up to 0.71. The detection is based on the entanglement between a magnetostatic mode and the qubit, followed by a single-shot measurement of the qubit state. This proof-of-principle experiment establishes the single-photon detector counterpart for magnonics.

中文翻译：

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具有超导量子位的单个磁振子的基于纠缠的单次检测

检测单个磁激发 量子增强传感是量子技术发展领域的近期应用之一。一种有前景的量子传感方法依赖于将控制良好的系统（传感器）与感兴趣的系统纠缠在一起，以检测后者中的激发量子。通过将超导量子位与亚铁磁晶体纠缠在一起，Lachance-Quirion 等人。证明他们可以检测到样品中的磁激发量子（磁振子）。高效单磁振子探测器的演示将有助于量子传感以及混合量子系统的有源组件，并应在量子技术中找到广泛的应用。科学，这个问题 p。425 超导量子位可以通过量子纠缠检测磁性晶体中的单个磁振子。基于超导电路的混合系统的最新发展为利用不同自由度的工程量子传感器提供了可能性。旨在控制和读出磁性有序系统中集体自旋激发的量子的量子磁学为磁性研究和量子技术的发展提供了机会。使用超导量子位作为量子传感器，我们报告了在毫米大小的亚铁磁晶体中检测到单个磁振子，量子效率高达 0.71。检测基于静磁模式和量子位之间的纠缠，然后是对量子位状态的单次测量。这个原理验证实验建立了磁学的单光子探测器对应物。