Where quantum machines once existed mainly as experimental set-ups, today they can actually be bought, and researchers are getting the chance to work with real quantum systems. Yet a fundamental question remains: will quantum computers really be able to deliver an advantage over classical machines? That is the subject of a conversation with Professor Remigiusz Augusiak, deputy director of the Center for Theoretical Physics of the Polish Academy of Sciences and head of the Center for Quantum-Enabled Computing.
Why do we need quantum computers at all?
A quantum computer uses quantum systems and phenomena to perform calculations. In theory, this could give a significant speed-up compared with classical computers.
Today, however, quantum machines are far from ideal. One of the main problems is noise and decoherence. Because of them, the quantum effects on which these systems rely quickly fade away, and the computer’s processing power diminishes along with them.
Which raises a natural question: why develop a new technology when classical computers are also constantly getting faster and more powerful?
The answer is simple: the potential of quantum computing is so great that it is worth testing in practice. Until we try to develop the technology, there is no way of knowing for sure whether it will one day outstrip classical systems.
The quantum computer as a “black box”
One of the intriguing problems of modern quantum science lies not only in building quantum computers but also in verifying that they really work as claimed.
A user may receive a ready-made device without knowing what goes on inside. It may have photons, qubits, lasers, detectors and other components at work in it, but for the user its inner design remains a kind of “black box”. What matters is something else: does the machine perform the task it has been set?
This is exactly why researchers are developing special methods for certifying quantum systems.
One of the foundations of this research is so-called Bell nonlocality. This quantum phenomenon is used to create tools for certifying quantum systems, operations and technologies. These methods are particularly important for quantum cryptography, where they can be used, for instance, to verify the security of a cryptographic key generated using quantum states.
Without looking inside
The most interesting thing about this approach is that you do not need to open up a quantum computer’s casing or examine all its internal components in order to check it.
Instead, ordinary, classical communication is used. The user puts certain questions to the quantum computer, the machine answers in ordinary bits of information, and the results are collected and analysed statistically.
Gather enough answers, and their statistics allow you to draw conclusions about what is happening inside the system: whether the computer is creating the right quantum states, whether it is performing the required operations and whether it behaves as expected.
In other words, we cannot see the inner mechanism, but we can judge how it works by its results.
The principle can be loosely compared to an ordinary cash machine. The user does not open the machine to check its electronics. They carry out transactions and judge the result. With a quantum computer the principle is similar, but mathematically and physically far more complex.
“Device independence”
The methods being developed are meant to be independent of the specific design of a quantum machine. That is why they are described as “device-independent” — that is, not tied to any particular device.
Such an approach has to be universal and make it possible to certify various multipartite quantum states. This is especially important because future quantum computers will work with such states.
Universality comes at a price, however. Methods like these are very sensitive to noise and other interference. So the current results are above all a proof of principle: a demonstration of what is fundamentally possible. The researchers show that such an approach works in principle, but that does not yet mean the method is ready to be applied to any real quantum computer.
The next stage is to create more practical methods that require fewer measurements and less statistical data while being more robust to noise.
From theory to real machines
One of the key tasks of the new Center for Quantum-Enabled Computing is precisely the move from theoretical results to experiments.
The researchers plan to work with experimentalists to test the methods they have developed in practice. Some of these methods have already been tested experimentally, but so far they work only in specific cases. Creating a universal method for different quantum systems and states is much harder.
Access to a real quantum computer plays an important role in this process. Under a joint programme with the Poznań Supercomputing and Networking Center, the researchers have been given the chance to work with a 20-qubit quantum machine. This will allow them to test their work directly on real hardware.
Quantum technologies need new specialists
Developing quantum computers is not just a matter of hardware and fundamental physics. It also takes people who know how to program and study such systems.
Access to a real quantum computer makes it possible to teach young scientists how to program quantum machines. The Center already has interested colleagues and master’s students, and doctoral students are due to join later.
If quantum computers really do live up to expectations and the technology goes large-scale, the specialists acquiring the relevant knowledge and skills today will have a significant advantage in the job market of the future.
What comes next?
Quantum computers are still at a stage of active development. They already exist as real devices, but they also face fundamental problems — noise, decoherence and the difficulty of verifying how they work.
So the next big step is not just about increasing the number of qubits. It is just as important to learn how to check reliably whether a quantum machine really does create the right states and perform the required operations.
And this is where a particularly interesting idea comes in: perhaps the quantum computer of the future will not need to be “opened up” to find out whether it is working properly. It will be enough to interact with it in the right way, ask the right questions and carefully analyse its answers.
And if quantum technologies really do live up to expectations, the next big question will be how to combine them with other areas of computing, artificial intelligence in particular. Then today’s experiments with “black boxes” may turn out to be just the beginning of a much bigger technological revolution.
Dr. Myroslav Trofymuk
Born in Lviv. Designer, director, musician, researcher, founder of ZEMLA STUDIO. Master of classical philology and digital marketing, PhD in the history of Ukrainian literature. Member of the National Union of Journalists of Ukraine. Since 2022 he has authored the CENTRUM MUNDI audio show for Polish Radio for Ukraine, continuing the same research into the contemporary music scene in Ukraine and Poland.
Full bio →
