Author: Alan Salari
Useful reference: Microwave Techniques in Superconducting Quantum Computers (Published by Artech House, 2024)
1. Introduction
The vast field of Quantum Information Science and Technology (QIST) consists of quantum computing, quantum communication, quantum sensing, and quantum simulation. These revolutionary technologies will soon begin to change the world around us rapidly. Many of them, such as secure quantum communication, quantum internet, and advanced quantum sensors, will be intertwined in our daily lives.
QIST is still an emerging field, and very few companies and research institutes can develop and apply these technologies. Much of the challenge can be attributed to the need for a highly skilled multidisciplinary workforce. The workforce in the QIST field must possess strong analytical thinking coupled with highly specialized skills in engineering and science.
The industry’s urgent need for more workforce in quantum jobs is discussed in Hughe’s et. al. in “Assessing the Needs of the Quantum Industry” [1]. Filling such roles can be difficult due to the time and effort required to train quantum engineers. The good news is that it is possible to speed up the training process and prepare the workforce to work in the QIST field in a much shorter time than previously imagined. This is possible by teaching essential real-world technical skills necessary for research and development in the quantum industry.
Quaxys is the first specialized academy for training quantum hardware engineers, offering exceptional skill-based quantum hardware courses. These courses focus on teaching the QIST workforce essential practical skills that prepare professionals to join the industry and conduct research as quickly as possible.
Quaxys proudly presents the pioneering book on superconducting quantum computer hardware, marking a significant contribution to the field. The first of its kind, Microwave Techniques in Superconducting Quantum Computers, introduces microwave and quantum engineers to essential practical techniques and theoretical foundations crucial for operating and implementing hardware in superconducting quantum processors. This practical resource covers an extensive range of topics, including Introduction to Quantum Physics, Introduction to Quantum Computing, Superconducting Qubits, Microwave Systems, Microwave Components, Principles of Electromagnetic Compatibility, Control Hardware for Superconducting Qubits, and Principles of Cryogenics. Such technical knowledge equips the reader with essential skills to succeed in the demanding industries and research settings surrounding quantum technologies. With clearly outlined learning objectives and coherent explanations of intricate concepts, this is a must-have reference for a wide spectrum of professionals, including microwave and quantum engineers, technical managers, technical sales engineers in quantum computing and microwave companies, as well as newcomers entering this field. To enrich the reader's experience, this book offers additional complementary content accessible via www.quaxys.com/book.
This article will focus on the skills of quantum engineers working on semiconductor quantum platforms such as superconducting, spin, and topological qubits.
2. Skill Sets for Quantum Hardware Engineers
Quantum computing platforms can be split into two categories. The first category includes natural quantum systems such as atom and ion qubits. The second category includes artificial atoms such as superconducting, spin, and topological qubits. Working with either of these categories requires special skills. Many of these skills are unique to each platform, while others are shared.
The following section will discuss the four main skill sets that a quantum engineer working on semiconductor qubits needs to master. These are:
- Cryogenic engineering
- Microwave engineering
- Nanofabrication
- Data acquisition
2.1 Cryogenic Engineering
Semiconductor qubit experiments are typically performed close to absolute zero at extremely low temperatures of 10mK-50mK. Such temperatures help suppress the noise that would otherwise cause the qubit’s fragile quantum states to collapse. Understanding the different parts of a dilution refrigerator and its workings is vital before conducting such experiments.
A dilution fridge protects the qubit from coupling to the environment. Therefore, the main task of a quantum engineer is to understand the paths (conducted and radiated paths) through which the noise gets coupled to the qubit and to block those paths using appropriate techniques.
An example here is to use filters, circulators, attenuators, shielding, and various cable types, such as lossy microwave cables, to minimize the noise level coupled to the qubit.
Quantum hardware engineers who utilize cryogenic techniques in semiconductor qubit experiments must also be familiar with DC wiring and amplification techniques inside the fridge. DC signals are mostly used for tuning purposes, whereas amplifiers bring the extremely weak signal levels from the qubit to a detectable level.
See here for an overview of a Quaxys course that covers the principles of operating a dilution fridge and a cryogenic setup inside the fridge. Courses like this one can help aspiring quantum hardware engineers learn the proper ways to conduct semiconductor qubit experiments.
2.2 Microwave Engineering
Measuring and controlling semiconductor qubits occurs at microwave frequencies. This means engineers working with semiconductor qubits must understand cryogenic and room-temperature microwave components and systems. This includes but is not limited to amplifiers, mixers, filters, power combiners, attenuators, and up-and-down converters. The vital knowledge in this area can be divided into three main areas
- Noise engineering, as mentioned in the previous section.
- Working with measurement instruments such as network analyzers and spectrum analyzers. These instruments are used to perform component level, system level, and qubit measurements. At Quaxys, we offer courses covering the fundamentals of the network and spectrum analyzer operation and practical tips and tricks to make accurate measurements.
- Microwave signal processing techniques include amplification, down-conversion, up-conversion, filtering, etc. These techniques are essential to control and measure the qubits by sending appropriate modulated signals to the fridge and downconverting the signals from the fridge for digital post-processing. The modulated signals are generated using microwave and arbitrary waveform generators.
Quaxys has a series of RF and microwave engineering courses that cover all the essential skills for the microwave engineering part of the qubit system.
2.3 Nanofabrication
Nanofabrication is typically used to create nanocircuits for semiconductor qubits. This is accomplished using an electron beam lithography machine. Familiarity with different fabrication techniques and metal deposition techniques, such as sputtering and thermal evaporation, is essential for fabricating high-quality qubits.
At Quaxys Academy, we will offer an in-depth course on the practical aspects of nanofabrication to get engineers acquainted with these machines and processes.
2.4 Data Acquisition
The last step in the chain of qubits experiments involves communicating with different machines, synchronizing them, and acquiring the measured data. This data is then sent to computers for post-processing.
Quantum engineers must be familiar with various communication protocols, such as serial communication, GPIB, LAN, and USB. Matlab, Python, LabView, and Labber are frequently used in the data acquisition stage. Quantum hardware engineers must be able to confidently work with at least one of the aforementioned software to ensure data acquisition is completed properly. Coding skills are also necessary when working with this software, especially if someone wants to develop codes for recording customized measurements.
Conclusion
Quantum hardware engineers must possess nanofabrication, cryogenic techniques, microwave engineering, and data acquisition skills to develop qubit systems successfully. The next generation of quantum engineers is a vital asset for accelerating the development of such revolutionary technologies, with effective skill-based training at the core of their success. Quaxys courses are intentionally designed to close the talent gap by focusing on real-world applications. Reach out to us for more information on custom packages and course offerings.
[1] C. Hughes, D. Finke, D. -A. German, C. Merzbacher, P. M. Vora and H. J. Lewandowski, “Assessing the Needs of the Quantum Industry,” in IEEE Transactions on Education, doi: 10.1109/TE.2022.3153841.
[2] A. Salari, "Microwave Techniques in Superconducting Quantum Computers," Artech House, Boston, 2024.