On-chip triple hybrid quantum systems: coupling microwaves to magnon-phonon polarons

“量子系统”描述了其中基本激发被量子化为小能量包的物理系统。例子包括光的单个光子、晶体的振动（声子）和磁系统的激发（磁振子）。控制这些基本激发的能力可以导致革命性新技术的发展，例如量子计算机，通过量子加密进行安全通信，以及用于导航，地球物理勘探和医学成像的传感技术。这些技术的关键是能够以一种连贯的方式在不同的物理系统之间转移能量量子，从而保留量子态中编码的信息。这是通过“重叠”或混合系统的量子态来实现的。许多研究小组正在研究如何在不同的物理系统中实现量子杂化。最近，一个被称为“腔自旋电子学”的研究领域已经实现了微波光子、磁振子和声子之间的量子杂化。然而，这些实验需要体积庞大的厘米级微波腔和毫米级大磁球，不适合技术应用的发展。我们提出的项目将开发一个完全在芯片上的架构耦合微波光子与磁振子和声子在一个微米大小的铁磁元件。片上架构将更容易与其他物理系统集成，如光学腔，声学谐振器和超导量子比特（量子计算机的构建模块）。首先，我们开发了一种新的方法，在薄磁性层中产生磁振子和声子态之间的大重叠，并在微米尺度的扩展磁性结构中证明了第一个混合磁振子-声子态。这是通过用浅的周期性条纹图案来图案化该层的表面来实现的，该图案产生声子和磁振子模式的限制并使它们重叠。其次，包括我们在日立剑桥实验室的项目合作伙伴在内的研究小组最近开发了将微波光子与芯片架构中的微米级磁性结构重叠的方法。这项提案将建立在这两个关键的发展，制造微波电路的电子芯片上含有微米尺寸的图案化的磁性结构，其中混合磁振子声子状态形成。与片上微波电路中的光子的重叠将导致所有三个系统（光子、磁振子和声子）之间的杂化。此外，微波电路可以很容易地控制和检测使用标准的实验室测量仪器。这将使我们能够利用微波激发和探测磁振子和声子。我们提出的完全在芯片上制造光子-磁振子-声子混合系统的建议将产生重大的技术优势，可能导致量子计算，通信和传感器技术领域的新应用。它将使人们能够研究光子、磁振子和声子的基本性质以及不同量子系统之间的相互作用。

"Quantum systems" describes physical systems in which the elementary excitations are quantised as small packets of energy. Examples include individual photons of light, vibrations of crystals (phonons), and excitations of magnetic systems (magnons). The ability to control these elementary excitations can lead to the development of revolutionary new technologies such as quantum computers, secure communication through quantum encryption, and sensing technologies for navigation, geophysical exploration and medical imaging. Crucial to these technologies is the ability to transfer the quanta of energy between different physical systems in a coherent way that preserves the information encoded within the quantum states. This is achieved by "overlapping" or hybridising the quantum states of the systems. Many research groups are working on ways to achieve quantum hybridisation in different physical systems. Recently, a field of research known as "Cavity Spintronics" has achieved quantum hybridisation between microwave photons, magnons and phonons. However, these experiments require bulky, centimetre-size microwave cavities and large, millimetre-size magnetic spheres, which are not suitable for the development of technological applications. The project we propose will develop a fully on-chip architecture for coupling microwave photons with magnons and phonons in a micron-size ferromagnetic element. The on-chip architecture will lend itself more easily to integration with other physical systems such as optical cavities, acoustic resonators and superconducting qubits (the building blocks of quantum computers).Our proposal will build upon two recent developments. Firstly, we have developed a novel method to create a large overlap between magnon and phonon states in thin magnetic layers and have demonstrated the first hybrid magnon-phonon state in a micron-scale extended magnetic structure. This was achieved by patterning the layer's surface with a shallow periodic stripe pattern, which created confinement of the phonon and magnon modes and caused them to overlap. Secondly, research groups, including our project partners at the Hitachi Cambridge laboratory, have recently developed methods to overlap microwave photons with micron-scale magnetic structures in on-chip architectures. This proposal will build upon these two key developments by fabricating microwave circuits on electronic chips containing micron-size patterned magnetic structures, in which hybrid magnon-phonon states are formed. The overlap with the photons in the on-chip microwave circuit will lead to hybridisation between all three systems (photons, magnons and phonons). Furthermore, microwave circuits can be readily controlled and detected using standard laboratory measurement instruments. This will allow us to excite and probe the magnons and phonons using the microwaves.Our proposal to make fully on-chip hybrid photon-magnon-phonon systems will yield significant technological advantages that could lead to new applications in the realms of quantum computing, communications and sensor technology. It will enable investigations of the fundamental properties of photons, magnons and phonons and of the interactions between the different quantum systems.