We present a case for developing a millikelvin-temperature transmission electron microscope (TEM). We start by reviewing known reasons for such development, then present new possibilities that have been opened up by recent progress in superconducting quantum circuitry, and finally report on our ongoing experimental effort. Specifically, we first review possibilities to observe a quantum mechanically superposed electromagnetic field around a superconducting qubit. This is followed by a new idea on TEM observation of microwave photons in an unusual quantum state in a resonator. We then proceed to review potential applications of these phenomena, which include low dose electron microscopy beyond the standard quantum limit. Finally, anticipated engineering challenges, as well as the authors' current ongoing experimental effort towards building a millikelvin TEM are described. In addition, we provide a brief introduction to superconducting circuitry in the Appendix for the interested reader who is not familiar with the subject.
Phonon-bottlenecked spin relaxation of Er$^{3+}$:CaWO$_4$ at milliKelvin temperatures
Tata Institute of Fundamental Research（塔塔基础研究所）；Indian Institute of Technology Madras（印度马德拉斯理工学院）；Chalmers University of Technology（查尔姆斯理工大学）；National Physical Laboratory（国家物理实验室）
A plug-and-play superconducting quantum controller at millikelvin temperatures enables exceeding 99.9% average gate fidelity
State Key Laboratory of Materials for Integrated Circuits, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences（中国科学院上海微系统与信息研究所集成电路材料国家重点实验室）；University of Chinese Academy of Sciences（中国科学院大学）；Graduate School of Science, Tokyo University of Science（东京理科大学理学部研究生院）；RIKEN Center for Quantum Computing (RQC)（理化学研究所量子计算中心）
CryoCMOS RF multiplexer for superconducting qubit control, readout and flux biasing at millikelvin temperatures with picowatt power consumption
Imec；Department of Electrical Engineering (ESAT), KU Leuven（荷语鲁汶大学电气工程系(ESAT)）；Proximus Chair in Quantum Science and Technology, department of Electrical Engineering (ESAT), KU Leuven（荷语鲁汶大学电气工程系(ESAT)普洛克西穆斯量子科学与技术讲席）
A near-quantum-limited diamond maser amplifier operating at millikelvin temperatures
Okinawa Institute of Science and Technology Graduate University（冲绳科学技术大学院大学）；National Tsing Hua University（国立清华大学）；Delft University of Technology（代尔夫特理工大学）；QuTech and Kavli Institute of Nanoscience（QuTech与卡弗里纳米科学研究所）；Liquid Instruments（液体仪器公司）；Brown University（布朗大学）
Adiabatic Cooling of Planar Motion in a Penning Trap Ion Crystal to Sub-Millikelvin Temperatures
Indian Institute of Technology Madras（印度马德拉斯理工学院）；University of Colorado, Boulder（科罗拉多大学博尔德分校）；National Institute of Standards and Technology（美国国家标准与技术研究院）
Quantum Orbital-State Control of a Neutral Nitrogen-Vacancy Center at Millikelvin Temperatures
Yokohama National University（横滨国立大学）；National Institute of Advanced Industrial Science and Technology（产业技术综合研究所）；National Institutes for Quantum Science and Technology (QST)（量子科学技术研究开发机构）
Ultralow-power coherent qubit control using AQFP logic at millikelvin temperatures
RIKEN（理化学研究所）；Tokyo University of Science（东京科学大学）；The University of Tokyo（东京大学）；National Institute of Advanced Industrial Science and Technology (AIST)（国立产业技术综合研究所）；Tohoku University（东北大学）；Yokohama National University（横滨国立大学）；Kobe University（神户大学）
Ultra-narrow homogeneous linewidths of erbium-doped silica glass fibers at millikelvin temperatures: magnetic field and temperature dependence
Institute for Quantum Science and Technology, University of Calgary（卡尔加里大学量子科学与技术研究所）；Department of Physics and Astronomy, University of Calgary（卡尔加里大学物理与天文学系）；Lawrence Berkeley National Laboratory, University of California, Berkeley（加州大学伯克利分校劳伦斯伯克利国家实验室）
Optimising Cryogenic Wiring for Microwave-frequency Millikelvin Quantum Processors
Sydney Quantum Academy（悉尼量子学院）；Centre for Quantum Software & Information, School of Mathematical & Physical Sciences, University of Technology Sydney（悉尼科技大学数学与物理科学学院量子软件与信息研究中心）
Statistical evaluation of 571 GaAs quantum point contact transistors showing the 0.7 anomaly in quantized conductance using millikelvin cryogenic on-chip multiplexing
