Quantum Sensing for the Hidden Sector (QSHS)

确定暗物质的性质是现代物理学的一个中心悬而未决的问题。暗物质主导着星系的质量分布，在我们对宇宙学的理解中发挥着关键作用。在过去的30年里，人们的注意力集中在弱相互作用暗物质(WIMP)上；然而，一个规模较小但活跃的团体一直在使用世界上一些最敏感的电子设备来寻找包括QCD轴子在内的“隐藏部门”粒子。轴子被用来解决所谓的强CP问题，即支配强相互作用的理论比我们目前的理论--量子色动力学--所说的更对称。但事实证明，轴子也是这种神秘暗物质的天然候选者。理论认为，轴子在强磁场中穿过微波腔时，应该可以通过它们发出的微小信号被探测到，大约是百万分之一瓦。这些信号甚至达到了使用低温冷却的超低噪声电子设备所能检测到的极限，但在过去几年里，在量子计算和测量的平行研究的推动下，在开发更新、更灵敏的量子传感器方面取得了快速进展，使轴子的探测变得触手可及。英国在这些新的量子设备方面拥有相当多的专业知识，这项提议旨在将这些关键的新测量技术应用于搜索隐藏的扇区粒子。我们提出的搜索包括两个主要部分。首先，我们联系了世界上最敏感的轴子搜索实验ADMX，提议建立一个英美合作伙伴关系。ADMX欢迎这种做法，并强烈鼓励我们参与。英国将在ADMX已经运行的磁铁和低温恒温器内设计和安装一个新的轴子探测器。使用这个探测器，我们将在我们银河系的暗物质晕中寻找在25到40微电子伏之间的质量范围内的轴子。这一范围与目前轴子质量可能是什么的理论的迹象很好地匹配，尽管可能的质量范围要大得多，因此有很大的基础要覆盖。这台英国仪器的核心将是我们自己的超导量子测量技术之一-测辐射热探测器、相干参数放大器、基于SQUID的放大器或基于量子比特的光子计数设备。将使用的技术将在参与机构进行广泛的表征后进行选择。然后，选定的技术将被集成到ADMX仪器模块中，该模块将在谢菲尔德大学专用的10 MK低温恒温器中进行表征。然后，这个低温恒温器将成为英国高场低温测试设施的第一个目标，这是我们提议的第二部分。第二，英国在隐藏部门物理方面的国际竞争力需要一个世界级的英国设施，其中包含一个极高的磁场磁铁：比用于医疗保健的核磁共振成像的设备大几倍。这样的磁铁对于轴子搜索是必要的，而轴子可以说是最有动力的隐藏部分暗物质候选者。磁铁的磁孔需要非常冷，才能让量子电子学工作，大约10mK。我们将与一家国家实验室合作，建造并运营一家符合这些规格的英国设施。许多隐藏的扇区搜索实验可以放在这个设施里，但第一个将是我们自己的低温量子光谱仪。最后，为了帮助保持英国在基础物理学方面的国际显赫地位，我们必须建立一个研究社区。隐藏部门物理学是一门快速增长的学科，一类全新粒子的发现将把粒子物理带入一个新时代，将量子电子学带入新的应用和市场。我们相信，所开发的技术和技术将在量子计算、通信和雷达等领域具有广泛的应用。

Identifying the nature of the dark matter that dominates the mass distribution of galaxies and that plays a key role in our understanding of cosmology is a central unsolved problem of modern physics. Attention over the past 30+ years has focused on weakly interacting dark matter (WIMPs); however, a smaller but active community has been searching instead for 'hidden-sector' particles, including the 'QCD axion', using some of the world's most sensitive electronics. Axions were invoked to solve the so-called strong-CP problem, whereby the theory governing strong interactions is far more symmetric than our current theory, quantum chromodynamics, say it should be. But axions also turn out to be a natural candidate for the mysterious dark matter. Theory suggests that axions should be detectable through the tiny signals they emit, about a millionth of an attowatt, while traversing a microwave cavity in a strong magnetic field. These signals are at the limit of what can be detected using even cryogenically-cooled ultra-low-noise electronics, but in the past few years, rapid progress in developing newer and more sensitive quantum sensors, fueled by parallel research in quantum computing and measurement, has placed the detection of axions within our reach. The UK has considerable expertise in these new quantum devices, and this proposal aims to apply these pivotal new measurement technologies to the search for hidden sector particles. Our proposed search has two main parts. First, we have reached out to the world's most sensitive axion search experiment, ADMX, proposing to form a UK-USA collaboration. ADMX has welcomed this approach, and is keenly encouraging our participation. The UK will design and install a new axion detector inside the magnet and cryostat that ADMX already operate. Using this detector, we will search for axions in our Galaxy's dark matter halo in a previously unexplored mass range between 25 and 40 micro-electron volts. This range is well matched to indications from current theories of what the axion mass might be, although the possible range of masses is far larger, and so there is a great deal of ground to cover. The UK instrument will have at its heart one of our own superconducting quantum measurement technologies - a bolometric detector, a coherent parametric amplifier, a SQUID based amplifier, or a qubit based photon counting device. The technology to be used will be selected after extensive characterisation at participating institutes. The chosen technology will then be integrated into the ADMX instrument module, which will be characterised in a dedicated 10 mK cryostat at the University of Sheffield. This same cryostat will then double as the first target in the UK high-field low-temperature test facility that forms the second part of our proposal.Second, an internationally competitive UK effort in hidden sector physics needs a world class UK facility incorporating an extremely high field magnet: several times larger than those used for MRI imaging in health care. Such a magnet is necessary for axion searches, and axions are arguably the best motivated hidden sector dark matter candidate. The bore of the magnet needs to be very cold for the quantum electronics to work, about 10mK. We will partner with a national laboratory to build and operate a UK facility meeting these specifications. Many hidden sector search experiments could be housed in this facility, but the first one will be our own low-temperature quantum-spectrometer.Finally, to help maintain the UK's international prominence in fundamental physics, we must create a research community. Hidden sector physics is a rapidly growing subject, and the discovery of a whole new class of particles would drive particle physics into a new era, and quantum electronics into new applications and markets. We believe that the technology and techniques developed will have applications in areas as diverse as quantum computing, communications and radar.