Quantum technologies are the next phase of the digital revolution

Photo. Tomasz Kowalczyk

Interview with Dr. Michał Parniak, laureate of the second edition of the Frank Wilczek Prize

By the decision of the Chapter of the Frank Wilczek Prize, you have been the laureate of its second edition for 'Development of new experimental platforms for quantum research and technologies and their use to demonstrate state-of-the-art quantum phenomena and protocols'. Experimental platforms for quantum research - what does that actually mean? Can it be explained in simpler words? Could you provide a true example of such a platform?

 

The award is a great honour for me and also a motivation to continue taking on challenging problems. Crucially, I have indeed worked on several platforms. Now in quantum technologies, we have a great variety of physical systems exhibiting fascinating characteristics that can give rise to compelling applications. The classical computers we have in our homes today involve a single, highly optimised platform based on copper and silicon. Their remarkable performance is made possible by the enormous engineering work underlying this platform. The quantum computers are still at an earlier stage, where there are twenty‑some platform schemes at present. We have just begun to identify those that have genuine potential, and that's why it's worthwhile to probe different platforms, which I've been actually doing. As a first example of my research, I implemented new protocols for processing information, particularly quantum information, using atoms. Atoms, such as caesium or rubidium, can be controlled very easily due to their relatively simple structure. And thus the atoms I used were laser-cooled and then used to store, process, and re‑emit light. During my work in Copenhagen, I also coupled the quantum states of such atoms to a macroscopic mechanical oscillator in the form of a tiny membrane made of silicon nitride. Extremely interestingly, it was possible to demonstrate the quantum features, that is, entanglement, of a macroscopic number of atoms and this macroscopic membrane. Therefore, these results were primarily important from a fundamental point of view. However, I do hope that further development of the aforementioned platforms will also contribute to their applications.

 

And what does this mean from the point of view of an average person: How will these technologies affect our lives and the lives of our children?

 

We have several basic pillars of quantum technologies and each of them can affect everyday life. Using computers and quantum simulators, where the atoms mentioned earlier are used for computation, we hope to design new medicines, for example. Quantum metrology is another subfield where also the atom arrays serve as very precise sensors, which could be useful in medical laboratory research. Finally, quantum communication makes it possible to send information that is protected by the fundamental laws of physics. This technology is already being implemented, although we do not see it in everyday life yet. All in all, quantum technologies contribute to the next stage of the digital revolution.

 

We have all heard that quantum computers are the future of computing. When do you think they could hit the ground running, i.e. go on mass sale as home appliances? It can sound strange, but after all, back in the second half of the twentieth century there were claims that there was no reason whatever for anyone to want to have a personal computer at home....

 

This is true, and actually right now it is difficult to find a reason why we would want a quantum computer at home. In principle, such a computer is not any faster than a normal, classical one or more powerful by default. However, there are certain algorithms and simulations that will run much faster on such a computer, using less physical resources and energy. Such problems, related to optimization and molecular design, for example, do not seem to be of interest to private users at the moment. So, I expect quantum computers to be available for the time being as external machines standing in a server room, accessible remotely. In fact, such devices are already available, on a small scale even to anyone! However, they still lack the memory or the sufficient number of qubits to solve truly practical problems. However, along with the development of hardware - which I, among others, am doing - also comes the development of algorithms and simulations.

 

And the quantum phone? Is the same technology also likely to work on mobile devices?

 

Quantum communication is a process that allows a cryptographic key, which is a sort of password, to be exchanged in a way that is fundamentally protected by the laws of physics. All it takes is for both the communicating parties to measure their entangled particles. They read out random but perfectly correlated sequences of zeros and ones. Then they can have a talk through an ordinary telephone, which is coded using the generated quantum key. And this is also how we will be able to connect to our bank in a secure way, so it is certainly worthwhile to push for widespread dissemination here. So, are we likely to have such a quantum key generation module in every phone? I think it might be not too far in the future, because the protocols that make this possible can use ordinary optical fibres, or light propagating in free space, in the air. Initially, such a quantum module will not be truly mobile, so we will start first with quantum landline phones, but I think this technology is closer than quantum computers.

 

How actually does a quantum processor work?

 

In a quantum processor, we generally process so-called qubits instead of bits. Each qubit can take on a state that is any combination of 0 and 1, a so-called quantum superposition. The quantum processor has to perform quantum gates on such qubits, which correspond to logic gates in the ordinary processor. It is easy to make gates involving only one qubit, while things get more difficult when we have to implement gates involving two and more qubits. We are also hindered by the decoherence process, which essentially consists in the qubit losing its quantum properties as the information is stored over time and, in fact, becoming an ordinary bit again, and often random at that. I have so far approached the problem somewhat sideways, implementing single-qudit gates, where the letter 'd' means that these are states going to larger sizes than two, that is, you can have any combination of 0, 1, 2 and so on, up to any, rather large number d. For example, in my quantum memory, we have reached d of the order of six hundred. In general, I would like to emphasize the multiplicity of possible modes of operation of quantum processors, because we can also have gateless models of quantum computers, such as the topological computing model or the clusterstate computing model.

 

Will communication using quantum protocols be faster still than the traditional optical fibres or high-speed backbone networks?

 

Surprisingly enough, potentially yes! I mentioned that typical quantum communication allows secure data transmission using a cryptographic key. However, we also have up our sleeves, at the moment still less popular, newer protocols that just aim at speeding up. By performing quantum operations on photons in a optical fibre, we are going to pack the information in them more densely, which means that the maximum speed of data transmission over the fibre increases. This enables one also to eliminate electronic circuits that introduce latency, which will ultimately reduce the ping response time familiar to gamers. We are also working on a fast and efficient conversion between the fibre and 5G radio networks, which will eliminate the inherent delays.

 

How do you envision the future of telecommunications? Put yourself in the shoes of an SF writer for a moment. What might the Internet look like in, say, a hundred years?

 

I think that inevitable in such a long time, perhaps even sooner, is the Internet using all‑optical and quantum-optimised devices, which would thus be enormously faster while consuming less energy. Hopefully, we will also have extremely easy conversions between different wavelength ranges (optical, radio), leading to even greater ubiquity of the Internet. Quantum technologies will also guarantee us security where we should need it most.

 

Let's go back to fundamental research. How does your own research work contribute to the development of theoretical and experimental physics?

 

The protocols that I have demonstrated are a kind of introduction. In my work, I always consider whether they can be implemented in other platforms. Thus, we manage to get much response from other experimenters who reproduce similar experiments in their systems. We can then compare the results and inspire theorists to go deeper. As for my experiments, they have such unique properties that also allow theorists to realize their visions, so I am happy to collaborate with them. However, as I pursue my research, I also increasingly run into difficult fundamental problems that require to be looked at in a different perspective jointly with the theorists. My everyday research work does not seem to touch the fundamental level to such an extent as particle physics or astronomy do because in principle I am actually trying to implement some new idea that is a bit contrary to nature. Essentially, the most interesting result is when the idea actually fails, if there is any fundamental reason unknown to date, or alternatively, if it turns out that experimental observations have analogues in, say, condensed matter physics.

 

What inspires you in your investigations?

 

Mostly the contacts with other scientists and with students doing research under my supervision. Just recently, that is, since 2020, I have managed to gather a very capable and dynamic team, consisting primarily of male and female students, from bachelor to doctoral level, from the University of Warsaw Physics Department; working along them on a daily basis is truly inspiring. From the point of view of physics, the experiments I do are extremely interactive and often allow me to see new interesting results almost every day. Here the inspiration comes from the fact that setting about working in the lab - which is after all quite enjoyable, involving manual construction of things or programming - we can immediately see quantum effects live.

 

What are your research plans for the coming years? Is there any other area of physics or engineering that you would like to pursue in the future?

 

Now I am intensively developing applications of Rydberg atoms, or highly excited atoms. Such an atom becomes almost macroscopic in size, which allows it to interact with other atoms – in order to implement quantum gates - or to receive external signals. I would like to build a device using such atoms to receive extremely weak microwave signals from, for example, radar or a radio telescope. This would allow this fascinating physics to underlie new technologies in telecommunications as well as in other fundamental research. The next step could be to use atoms to detect light forming an image without destroying it within the accuracy of individual photons, which ultimately should give rise to a completely new class of cameras. Recently, I have been spending more time trying to raise funds for this planned, ambitious, and, I should admit, risky research. In the future, I would like us to explore questions of both fundamental and applied type in our laboratory.

 

This is all incredibly interesting! Thank you very much for the interview and I wish you further success in your future endeavours!

 

Interviewer: Elżbieta Kuligowska