Quantum Microwaves for Communication and Sensing

In this interview, AZoNano speaks to Frank Deppe, Junior Group Leader for Superconducting Quantum Circuits at the Walther-Meißner-Institut, about QMiCS and the work that it does.

Can you give a brief overview European Quantum Technology Flagship Program ‘QMiCS’?

The project acronym ‘QMiCS’ means “Quantum Microwaves for Communication and Sensing”. QMiCS is one out of 20 projects which got funded in the highly competitive first call of the European Quantum Technology Flagship Program. Within this program, QMiCS is still a basic science project, where academic research groups collaborate with selected commercial companies. The main task of QMiCS is to explore the potential of non-classical propagating microwaves, whose behavior is controlled by the laws of quantum mechanics, for future applications and commercial exploitation.

Can you please explain the basic concept behind microwave applications and nano-structured circuits?

Micro- and nanostructured superconducting circuits have allowed for the demonstration of quantum mechanical effects with an unprecedented degree of control in the last two decades. For this reason, they have become a key candidate for the realization of universal fault-tolerant quantum computing. It is the engineering potential of superconducting quantum circuits, which has enabled the recent result on quantum supremacy over our classical supercomputing centers recently published by Google. The research and development efforts of the QMiCS consortium are now strongly motivated by the fact that such superconducting quantum processors naturally operates in the microwave regime. The underlying idea is that propagating microwaves are the natural carrier of information between quantum devices based on superconducting circuits. Specifically, we use nonclassical squeezed microwaves emitted by superconducting circuits for secure quantum communication, distributed quantum computing, and improved quantum sensing.

What applications do these circuits have?

Superconducting circuits themselves cover the whole spectrum of quantum technology: quantum computing, quantum simulation, quantum communication, and quantum sensing & metrology. The propagating continuous-variable quantum microwaves investigated within QMiCS are most promising for quantum communication and quantum sensing. In quantum microwave communication, a quantum local area network would allow for intrinsically secure communication and for distributed computing between multiple quantum processors. With respect to sensing, the most compelling application of quantum microwaves is quantum radar, where theory promises up to 6dB improvement in signal-to-noise ratio over the best possible non-quantum realization. Although the quantum properties of propagating microwaves are nowadays well established, their use for applications still needs to be demonstrated. Here, QMiCS aims for important advances. Challenges will be the realization of suitable superconducting quantum LAN cables and the development of strategies to deal with ambient conditions such as elevated temperatures or our atmosphere. A solution to these challenges will require progress in both experiment and theory models.

What role does Oxford Instruments have during this partnership?

Superconducting quantum circuits usually work at temperatures on the order of one-hundredth of a degree above absolute zero. Oxford Instruments is a renowned expert on making the high-quality cryostats required to reach such temperatures. As a part of QMiCS, Oxford Instruments develops the cryogenic part of a six-meter-long quantum LAN cable connecting two cryostats at these low temperatures. Such a system will be installed at the Walther-Meißner-Institut in Garching, Germany, where the scientists will equip it with special superconducting microwave cables and perform first microwave communication experiments between two different labs. The cryolink developed by Oxford Instruments could be used to connect future off-the-shelf quantum processing units.

What are the benefits of working with Oxford Instruments?

Nowadays, the development and production of cryostats is not an academic “first-time” result anymore. It is of outstanding importance to collaborate with so-called “enabling” industry partners providing key non-quantum technology required to make quantum technology work. The result is a win-win situation: the companies develop innovative products helping to advance science and, in turn, stay close to cutting-edge research defining their future markets. In my opinion, the commitment of Oxford Instruments as a funded partner was an important reason for the success of our project application. In my role as coordinator of QMiCS, I appreciate the mix of focused work, technological expertise, and open-mindedness present in the project team from Oxford Instruments. As a scientist, I can also see that Oxford Instruments is used to work with partners from academia.

What is the long-term vision of ‘QMiCS’?

Currently, the quantum aspects of QMiCS are still in the realm of basic science. Nevertheless, our industry partners develop enabling products – cryotechnology and microwave amplifiers. Furthermore, we plan to combine our results to a “roadmap to applications” after three years at the end of the project. The long-term vision of QMiCS is to create commercial applications for propagating quantum microwaves at both millikelvin and room temperature.

How do you foresee Oxford Instruments assisting ‘QMiCS’ in realizing this vision?

Already the ongoing development of the cryolink between two cryostats suitable for superconducting quantum circuits is a super-important milestone. Nowadays many people trust the predictions of quantum mechanics, but the possibility to engineer such a cryolink has been doubted even by many colleagues who are not so familiar with cryogenics. I expect that the combination of an operating prototype and commercial availability of the cryolink will inspire more groups and companies to enter into the fields of quantum microwave communication, distributed quantum computing, and quantum microwave illumination. In this way, we can move faster towards real-life applications.

Where can readers find out more about your organisation?

You can visit the following websites: www.wmi.badw.de or qmics.wmi.badw.de

About Frank Deppe

Frank Deppe is Junior Group Leader Superconducting Quantum Circuits at the Walther-Meißner-Institut and Private Lecturer at Technische Universität München in Garching, Germany. He holds a PhD in physics and has conducted cutting-edge research on superconducting quantum circuits and propagating quantum microwaves for more than 15 years now. Since October 2018, he coordinates the European Quantum Flagship project “Quantum Microwaves for Communication and Sensing” (QMiCS).