Himadri Majumdar, manager of quantum technology at VTT, discusses the research centre’s role in delivering quantum technology to Finland and Europe.
In the last few decades, digitalisation has disrupted almost every traditional industrial sector. Digitalisation is predominantly based on increased computing power; and the next step in accelerating computing power is quantum technology, one of the most interesting and disruptive scientific fields of the 2020s. While an ordinary computer calculates using bits, or ones and zeros, a quantum computer uses qubits, which can be ones, zeros or superpositions of both, each with their own ‘weighting’ or probability. The large number of possible states and a phenomenon called entanglement allow quantum computers to achieve an astonishing computing power for certain computational tasks – provided that the qubits perform reliably. During the starting decade, quantum technologies are making the breakthrough from research laboratories to more extensive commercial use.
Quantum computing power could enable, for instance, the extraordinarily rapid development of medicines and vaccines, thereby disrupting healthcare worldwide. Modelling complex molecules, such as protein and drug molecules, is traditionally difficult due to their large size and complex interactions. Even today’s supercomputers cannot create precise molecular simulations. But since all molecular structures are determined by the laws of quantum mechanics, it has been proposed that a large quantum computer could model the structure and activity of these molecules more precisely and rapidly. In the future, we could also use large quantum computers to solve huge systemic problems. For instance, they could help to find new ways to produce sustainable energy or develop sustainable materials. Thus, quantum computing may help us meet the challenges of climate change and resource scarcity with unbelievable efficiency.
If Europe gains a foothold in quantum industrial development, we can grow a new branch of the tech industry worth billions, employing thousands of people and serving the needs of the whole world. There are several aspects of quantum technology in which European countries are advanced. Finland, for instance, has profound expertise in developing electronics, superconducting circuits and sensors. This expertise has deepened over decades in quantum and low-temperature physics laboratories, which has already led to successful quantum technology companies.
Finland’s first quantum computer
In Finland, we are taking the first steps already. VTT and Finnish startup IQM are currently co-developing Finland’s first quantum computer as part of a €20.7m public procurement project funded by the Ministry of Economic Affairs and Employment. In the first phase, we are concentrating on expanding the technical capabilities: our aim is a functioning five-qubit quantum computer which will demonstrate our expertise in building quantum computers. The overall goal of the project is to build a much larger, 50-qubit device by around 2024. We can use this computer to develop new quantum algorithms which can be applied to solve demanding problems in the future. Besides developing a quantum computer, it is important to strengthen quantum technological expertise across the board, from building the computer itself to applying algorithms and quantum computing to solve practical problems. This development will also be supported by the Finnish IT Centre for Science’s (CSC) quantum computing simulator and new supercomputer LUMI.
VTT’s quantum technology activities
The heritage
VTT and Finland are well positioned for joining, and even leading the quantum revolution. We have a long tradition of world-class research and education on quantum physics, from theoretical and computational science to experimental and applied physics. On the applied side, VTT has been developing superconducting devices for quantum applications for decades. VTT is jointly running in a 2500m2 cleanroom that includes processes for superconductive, nano and quantum devices.
The biggest success story has been the development of a stable process for Josephson junctions, which are the basis of many quantum devices even today, and in particular, the superconducting transmon qubit. Josephson junctions enabled us to build superconducting quantum interference devices (SQUIDs), a versatile type of quantum device which can be used as an amplifier, a sensor or a non-linear element. SQUID magnetometers are the most sensitive magnetic field sensors, and these are used in magnetoencephalography (MEG) for mapping brain activity by measuring weak magnetic fields that arise due to normal neural activity. VTT has been producing the SQUID magnetometers that go into these diagnostic devices for over a decade.
Furthermore, a long tradition in applied superconductivity, nano and quantum research has enabled us at VTT to develop sensitive THz, IR and X-Ray detectors for security imaging, thermal imaging and diagnostic imaging, respectively.
VTT also has a matured silicon photonics platform developed within the same cleanroom and combining that with superconductive devices allows us to develop integrated single-photon detectors and sensors. This also enables new quantum communication and sensing possibilities.
Scaling up superconducting quantum computers
In the past few years we have seen remarkable progress in the field of quantum computing, both in hardware and in algorithms. In software, especially error correction, algorithms have gained momentum. In hardware, a few different platforms have emerged, especially superconducting qubits – the platform of choice for VTT. However, there are still significant challenges in building quantum processors of sufficient size for addressing real world problems. VTT, with its strong focus on industrially relevant R&D is in a very good position to address many of these challenges. We are not too focused on large-scale production nor on academic proof-of-principle one-offs but have a more pragmatic approach to develop components that allow for scalability.
We are currently in the ‘Noisy Intermediate-Scale Quantum’ (NISQ) era – which means significant applications can be expected already in the short- and medium-term with a limited number of noisy qubits. However, it is generally agreed that universally useful quantum computers will require about one million qubits. To date, most advanced universal quantum computers are based on superconducting transmon qubits and operated at temperatures close to absolute zero, in order to minimise thermal noise. Electrical transmission lines are used to carry the electrical signals driving and reading the transmons inside the cryostat. This approach is perfectly fine when dealing with a few hundred qubits, but starts becoming challenging for thousands of qubits, and not viable anymore when approaching one million qubits, given that electrical cables come with limited bandwidth, high crosstalk, and high thermal conductivity. For these reasons, at VTT we are pioneering the next generation of communication interfaces for cryogenic qubits, using optical fibres and suitable optoelectronic cryogenic converters.
Another challenge that VTT is addressing is 3D integration of quantum systems. 3D integration of classical microsystems is broadly available technology, but for quantum it has just started and VTT is working on it, for example, in multiple European quantum flagship projects. Although current quantum error correction codes work on a 2D lattice of qubits we still need to bring in control and readout lines to each qubit. In purely 2D architectures we need to bring these lines in from the sides, which is clearly not scalable. In practice the limit is around 20 qubits. With 3D integration, we can have a 2D lattice of qubits on one chip (‘qubit chip’) and use one or more control chips for routing the auxiliary lines (control & readout), possibly with ‘interposer’ chips for setting vertical distances. The chips are connected to each other by superconducting flip chip bonding. Superconducting through-silicon-vias (TSVs) are used for electrically connecting opposite sides of the chips. Ultra-low microwave losses are crucial in order not to kill the quantumness and this is a significant technological challenge.
Another specific challenge in the scaling we address is qubit readout in large superconducting quantum processors. We are making wide-band ultra-low noise microwave amplifiers that allow frequency multiplexed readout of many qubits using a single physical output line (coaxial cable). Our approach is based on superconducting travelling-wave parametric amplifiers (TWPAs) based on Josephson junctions. The noise added by Josephson junction-based parametric amplifiers is unparalleled: in fact it is nearly quantum limited. Together with the wide bandwidth of TWPAs, they are an unmatched solution for superconducting qubit readout and near-term quantum computer scale-up. In the long-term, VTT sees tighter integration of digital electronics as an important step in scaling to larger processors. This may include both superconducting and semiconducting ASICs tailored to specific needs and the unique requirements set by cryogenic operation.
Solid state coolers developed at VTT can one day enable reducing the size of the dilution fridges currently used for the cooling down of quantum computers. With the increase of the number of qubits the size of the fridges is expected to grow. We already hear about monster fridges to be used in next generation quantum computers. VTT’s solid-state coolers can supplement the cooling capacity of existing fridges by doing the last stage of the cooling, which will minimise the need for monster fridges and can help repurpose existing fridges for a higher number of qubit machines.
VTT has also developed a custom complementary metal oxide semiconductor (CMOS) platform targeting, especially, different single electron operation functionalities. CMOS is the most mature and complex microsystem to date, driving our mobile phones and PCs. Small Si transistors of the CMOS architecture can also be operated as qubits; when cooled close to absolute zero they reach the limit where the operation is dictated by transport of single electrons and coherent quantum phenomena. By this approach several decades of successful CMOS circuit development can be made to serve the quantum revolution. CMOS circuits also provide an attractive route for classical interfacing for different kinds of qubits. Driven by the special requirements of the quantum systems and the low temperature environment, a high level of customisation is needed in the CMOS platforms.
VTT’s algorithm experts are working together with experts from specific domains such as synthetic biology, material science and cybersecurity in order to identify novel real-world problems and applications for quantum computing. As an example, we are developing quantum graph analysis algorithms for metagenomics data to identify new microbial species. The graph analysis includes community detection, i.e. detecting sets of nodes that are densely connected internally, which is a known hard graph problem, maybe a potential candidate for showing quantum supremacy in a real problem. On the other hand, related to a biotech problem of finding new microbe species in field samples, 16S-metagenomics data can be represented as graphs and the detection of novel species can be defined as finding communities in those graphs. Thus, by applying a quantum graph algorithm to 16S-metagenomics graph data we introduce a new quantum algorithm to bioinformatics that could provide advantages in processing time or result quality when computers develop further.
At the same time, we are aiming to apply graph algorithms to other big data problems that can be represented as graphs in order to understand the data and underlying phenomena, and to pre-process data for machine learning and AI applications. Detected communities provide means to find similarities in the graph structure and ways to reduce the amount of data preserving the main features in the information contents, thus enabling simpler machine learning models to be used on the data for faster learning and processing.
VTT hopes to solve some of the future scalability challenges facing the quantum computing community based on the approaches mentioned above. Some of these will already be demonstrated in the first quantum computer currently being built by VTT and IQM.
VTT’s role in the Finnish quantum ecosystem
VTT works very closely with Finnish universities and research organisations with expertise in quantum technologies, from hardware to software. VTT has a longstanding collaboration with Finnish universities and research organisations. One such partner is Aalto University which includes a joint professorship. Such collaboration with universities has led to many high-impact publications on the topic of quantum technologies. VTT has been part of three national Centres of Excellence in Quantum research since 2006. The latest one is the Quantum Technology Finland (2018-2025, coordinated by Aalto University). This collaboration is expected to evolve further in the near future. VTT’s role in the ecosystem is to drive innovation and create technologies and solutions suitable for commercialisation.
The cleanroom facility mentioned earlier is a backbone of Finnish Quantum research infrastructure. In addition, there are multiple characterisation and metrology facilities that enhance VTT and Finland’s capabilities.
VTT collaborates with another Finnish research organisation, CSC, on the topics of quantum algorithm. CSC is in the process of building the LUMI supercomputer which will be linked to the first Finnish quantum computer to enable the initial application of hybrid computation. The goal is to enhance the performance of classical supercomputers with quantum computers before high-power quantum computers become an independent computation method for specific computational problems.
Even though the ecosystem is predominantly focussed on education, research and innovation the role of industry is strong. VTT has identified the need for engaging industry early in the innovation process. This involves both enabling and end-user companies. The enabling companies are closer to the innovation value-stream where they get involved in creating new businesses and solutions, both in hardware and software. For these companies, the ecosystem is a necessity to build their business. The end-user companies are further along the value stream but remain an integral member of the ecosystem community. They are going to be the ones who will adapt the quantum technologies in their businesses and propel the success. For such companies the ecosystem serves multiple purposes, from staying up to date with the state of the art by learning from experts and allowing them to engage at the right time, to finding potential business partners and enabling quick access to a future workforce. VTT believes that the success of quantum technologies is intertwined with the success of this ecosystem.
VTT’s short- and long-term visions of quantum in Finland and Europe
At VTT we have a pragmatic approach to quantum. Whilst there is strong academic progress in quantum in recent times, we want to ensure that we make choices that lead to commercialisation of the technology for maximum benefit to society. This leads us to the proposal of a timeline. Having said that, we also acknowledge the importance of disruptive innovation and do not make our path rigid. We acknowledge the speed of innovation globally and have, therefore, kept our vision agile to allow ourselves to adapt and adopt new, disruptive innovation without delay.
2020–2025: We expect European countries to invest in developing and using functional quantum computers. Investment in quantum technology comes from both the private and public sectors. European-level cooperation between research centres, development and innovation in quantum data communication and sensors is strengthened.
2026–2030: Quantum computers approach quantum advantage in certain applications. Quantum computers start to be used more widely in various fields of industry. Work on developing quantum data communication and sensors starts to bear fruit: quantum sensors enable new applications, for example, in medical and autonomous machine imaging. Data communications starts to make use of long-range communications protected by quantum technology.
In the 2030s, quantum computers are expected to be in general use, enabling efficiency savings in production processes for selected tasks such as drug development. Learning from the experience gained in the 2020s, European companies create sufficient expertise in creating quantum technology, and start exporting quantum machines, sensors, data communication components and parts, and collaborating with other international leaders in the field. By the 2040s, we will be doing such amazing things with quantum computing that they are impossible to predict from where we stand today. I believe, however, that exponential computing power can lead to an exponential leap in productivity, which will enable us to apply the Earth’s resources to benefit the well-being of a growing global population. This also means economic growth for Finland and Europe at large, if we manage to create global players on the quantum technology market.
Whether in forestry innovations or electronics, Finland’s success has always been founded in high-level expertise and exploiting new technology fast. The same goes for Europe as a region. Now, we should use the momentum to find new areas that play to our strengths and create long-term wellbeing. We have disrupted the world before. We can do it again. Let’s start today.
The contributors to the article are Dr. Pekka Pursula, Dr. Matteo Cherchi, Dr. Mika Prunnila, Dr. Joonas Govenius and Dr. Ville Kotovirta
