World-renowned researchers had their eyes on Copenhagen when Niels Bohr changed the world with his theories of quantum physics. Quantum research at UCPH is once again attracting international attention. In a new major project, Associate Professor Morten Kjaergaard and his team have built Denmark's largest quantum computers. Now they start experimenting.
When the tiny chip in the quantum computer reaches minus 273 degrees, the magic happens. Particles begin to behave according to the unfathomable laws of quantum physics. Yet, despite their baffling nature, these laws also provide the potential for quantum computers to tackle some of the world's greatest challenges.
"If quantum mechanics hasn't profoundly shocked you, you haven't understood it," said Danish physicist Niels Bohr nearly a century ago. But Associate Professor Morten Kjaergaard from the University of Copenhagen keeps a steady hand as he engineers the development of Denmark's most powerful quantum computers.
If quantum mechanics hasn't profoundly shocked you, you haven't understood it
The adventure started in 2007 when Morten Kjaergaard was an undergraduate student of physics. Now he leads a huge quantum initiative at the University of Copenhagen.
This year, he and his research group are taking a giant leap forward as they power up one of Europe's largest quantum computers. They aim to explore how Bohr's principles can be applied to an entirely new kind of supercomputer.
The challenges are numerous, and no one yet knows the full potential of quantum computers. Can they accelerate the green transition? Teach us more about the fundamental building blocks of the universe? Or pave the way for more efficient biochemical research to develop medicines?
Scientists and world leaders have high hopes.
In just a few years, Copenhagen has again become a hub for international quantum research, much like during Niels Bohr's time one hundred years ago.
When the new quantum computer centre reaches its maximum capacity, the two new quantum computers can study up to 25 quantum bits - or qubits - simultaneously. That's about five times as many as Denmark’s current second-largest quantum computer.
Computer vs. quantum computer
In 2019, Google succeeded in using 53 superconducting qubits in a quantum computer to do a calculation in just three minutes. The world's largest supercomputer is estimated to take about four weeks to do the same calculation, even if running at absolute full capacity.
IBM's Summit supercomputer has billions upon billions of ordinary bits and is built around thousands of connected servers.
It occupies no less than 520 square meters and weighs more than 340 tons. A quantum computer, including all equipment, weighs a few hundred kilos and fits easily in a standard office space.
The shiny, open quantum computer is a rare sight even for researchers When turned on, it’s wrapped in multiple layers of insulation to maintain the freezing temperature level that is essential for it to work. When a component is replaced, the insulation layers are removed, and the cryostat must then become warm enough to work with. When the component has been replaced and the computer is sealed, the long cooling process begins.
Many of the components of the computer are coated in gold. Gold reflects heat and keeps heat away from the parts of the computer that need to be near absolute zero to function.
Morten Kjaergaard chiefly describes himself as a quantum mechanic. He is particularly interested in the development and construction of the actual mechanics – the fundamental building blocks – of a quantum computer. As an associate professor and project group leader at QDev – Center for Quantum Devices and NQCP – Novo Nordisk Foundation Quantum Computing Programme, he is currently involved in building the new quantum computer.
With a large team of research colleagues and students, Morten Kjaergaard is determined to make qubits more stable and usable. When he was a student, it was hard to imagine that one day Denmark would host multi-million kroner projects developing quantum computers.
Extreme cold
A quantum computer like this consists of a freezer – a cryostat – with a quantum chip at the bottom.
It has taken three Nobel Prize discoveries to reach the point where a cryostat is cold enough to make a quantum computer work. The cooling is done by means of helium.
The final degrees of cooling towards absolute zero are done by two cylinders to the right in the picture. Behind one of the other key components is a Danish startup originating from UCPH.
Building advanced quantum computers requires both practical ingenuity and meticulous planning. Before the computers get suspended, the research group has carefully planned every detail and selected every component in the computers.
One week's work is condensed into one minute:
Morten Kjaergaard's journey into the world of quantum computers began in 2007. A passing remark about quantum computers from a lecturer on one of his first physics courses piqued his interest.
“I’ve always been a computer nerd and built computers all my life. So when I first heard about the possibility of combining quantum physics and computer science, I was hooked," Morten Kjaergaard says.
His interest in quantum computers has led him to elite groups at Harvard University and MIT (Massachusetts Institute of Technology) in the US, where he was trained by leading international quantum computer researchers.
If we talk again in a few years, you won't hear me say 'damn, the quantum computer still can't calculate something super complex'.
In 2020, he returned to where it all began: the Niels Bohr Institute at the University of Copenhagen. His research group, SQuID Lab (Superconducting Quantum Information Devices Lab), conducts research into innovative methods to develop and use superconducting quantum computers. Alongside other research groups, his group is working to develop a foundation that allows calculations currently inconceivable for ordinary computers. While major tech companies such as IBM and Google focus on creating large and efficient quantum computers, SQuID Lab is uniquely positioned to both experiment with and optimise the computers.
The biggest challenges
Quantum computers are built in freezers, known as cryostats because the particles in the qubits are unstable and hypersensitive to external influences such as temperature fluctuations. The freezer goes all the way down to minus 273.14 degrees. That's one hundredth of a degree above absolute zero – and about 100 times colder than outer space.
The tiny processor, which is actually the quantum computer – a collection of qubits – is the computer's brain and sits at the bottom of the freezer. This is where the particles, which must not be disturbed, reside. Even in the ice-cold freezer, they are only stable for 1/10,000th of a second before becoming unstable again. This makes it difficult to retrieve the final calculations requested from the computer.
The group conducts theoretical and practical experiments to develop and test different types of superconducting qubits and, crucially, explore how they can maximise the processing power of each qubit.
It's almost as if nature is urging us to seize this opportunity
The researchers don’t know whether they have found the definitive method for constructing the type of quantum computers that will be necessary in the future so we can use their processing power more broadly and not only for research. That’s why the experimental approach makes good sense.
“If we talk again in a few years, you won't hear me say 'damn, the quantum computer still can't compute anything super complex'. No matter what, I'm sure that by then we'll have gained a deeper understanding of how to develop quantum computers.” More importantly, we have learned from our mistakes along the way. And in the process contributed to valuable research and education,” Morten Kjaergaard says.
Quantum mechanics is the underlying theory of quantum computers. It has such intricate consequences that even Albert Einstein went to his grave without being able to accept several of them.
For example, that particles can be in a so-called superposition. Superposition also plays a crucial role in the capabilities of quantum computers.
We can offer them cutting-edge research opportunities with some of the best equipment in the world
Imagine a regular computer as a box of small devices called bits. The number of bits determines a computer's processing power. Each bit consists of transistors that can either be on (1) or off (0).
Understanding the difference
Svend Krøjer Møller, a postdoc in SQuID Lab, explains below why superposition makes quantum computers so much faster than regular computers (only in Danish).
The complexity lies, among other things, in that the particles cease to be in superposition when measured. It sounds incomprehensible. Morten Kjaergaard is still amazed at how surprising and complex quantum physics is. But for him, the most important – and the most fascinating – thing is that the theory holds up in practice and that we can build a computer that exploits Bohr's century-old principles. And perhaps, in the future, quantum computers can solve what today is unsolvable by using the incredible laws of quantum physics.
“Having attained the ability to control nature so accurately that we can construct quantum computers is utterly insane and fascinating. Regardless of the applications a future quantum computer may have, it's almost as if nature is urging us to seize this opportunity. And with the technology and sophisticated understanding of qubits we have today, it's an invitation we can't refuse,” Morten Kjaergaard says.
Quantum magic: Entanglement
Superposition alone is not ‘enough’ to create qubits and ultimately quantum computers. Quantum mechanical systems also exploit another equally incomprehensible quantum capability: Entanglement. Entanglement allows two qubits in superposition to behave identically – not just somewhat, but completely identically. So if two qubits in superposition have interacted, they will subsequently be entangled and behave in exactly the same way. Even if they are very far apart.
So, the moment one qubit collapses from its superposition, the other also collapses. And if one qubit collapses to 1, the other will also collapse to 1 – completely simultaneously.
Imagine two qubits as spinning tops. When they spin, they are in superposition – as in the video with Svend. If these two spinning tops come into contact with each other, they become connected forever. No matter where they are in the universe, they will behave identically. So if one spinning top stops at red, the other will stop – also at red. Not just a little later, but in exactly the same millisecond – regardless of whether the distance between the two spinning tops spans borders, planets or solar systems.
Morten Kjaergaard has carried his vision for the future into his leadership of the research group SQuID Lab. Here, young researchers, PhD students and senior researchers follow in the footsteps of legends as they delve into waves, particles and algorithms through the complex electronics of quantum computers. And there is fierce competition to join the team.
"We attract some of the brightest students from all over the world. We can offer them cutting-edge research opportunities with some of the best equipment in the world, including the lab we’re setting up just now, so together we can push the boundaries of quantum computer research," Morten Kjaergaard says.
He prioritises training and teaching students - an approach he learned from the professors who were his mentors when he was a student and researcher at some of the best universities in the world.
“We gain tremendously because these young talented students come with new and creative input – and they help build a pleasant atmosphere where everyone feels comfortable,” Morten Kjaergaard says.
Some of the group explore the frontiers of quantum physics while others focus on how best to link qubits or experiment with avoiding errors and interruptions when working with multiple qubits simultaneously.
Ministers and world leaders see great potential
Rumours of a uniquely strong quantum environment attract the brightest minds from all over the world to Denmark and Copenhagen. In just a few years, Copenhagen and its environs have become home to research environments and start-ups that base their business on quantum technology. The attention of ministers and world leaders, who see the potential in quantum technology, is undeniable.
"This reflects our strong international position in the field. I’m also pleased to see how the project encourages close collaboration across businesses, universities and the healthcare sector. It aligns perfectly with the government's strategic research programme, which we launched earlier this summer with a national strategy for quantum technology; hopefully, the project can bring quantum technology closer to providing solutions in areas such as healthcare and climate," says Christina Egelund, Minister for Higher Education and Science, about the quantum computer effort.
The work Niels Bohr set in train over 100 years ago has been carried forward by researcher after researcher. Like Morten Kjaergaard, they have insisted on contributing to scientific breakthroughs. The whole world has recognised that, once again, the Niels Bohr Institute and Denmark host a top-class quantum physics research environment. And who knows? Perhaps the next major quantum breakthrough will happen right here in Copenhagen.
About the project
The new quantum computers at the University of Copenhagen are supported by the Novo Nordisk Foundation Quantum Computing Programme (NQCP) and Applied Quantum Computing Denmark (DanQ, supported by Innovation Fund Denmark). Research in the lab is also part of the NQCP centre, which focuses on improving sensitive qubits through advanced materials research to develop components for future quantum computers.
Over the next four years, the researchers in the project will be working with leading quantum researchers from the Massachusetts Institute of Technology (MIT) in Boston. With two identical quantum computer setups, they will run parallel experiments, compare results and exchange both researchers and ideas.
Questions or comments?
Please contact medieteam@adm.ku.dk
Pictures by Nikolai Linares