Quantum Computing and Its Engineering Challenges

At the heart of quantum computers, citing information from djcse.in, are the principles of quantum physics – the very ones that perplex even scientists: superposition, entanglement, quantum tunnelling. But if we omit complex terminology, quantum computing is a new way of processing information, which is radically different from the logic of classical computers that we are used to.

Devices That are Difficult to Build

In a classical computer, everything is based on bits – elements that take the value 0 or 1. A quantum computer works with qubits – quantum bits that can be both 0 and 1 thanks to superposition. This opens the way to parallel computing: a single qubit can do more work than a classical bit. And when there are hundreds or thousands of such qubits, the speed and power of such machines potentially become millions of times higher.

To create a working quantum computer is not just difficult, but very difficult. Firstly, a qubit itself is not a physical button or transistor. A qubit is a fragile state of a particle that must not only be created, but also held long enough to perform calculations. In practice, this means that qubits need to be isolated from the rest of the world, because any external influence destroys their state.

There are several technologies for realising qubits. The most advanced today are superconductor qubits (used, for example, in the developments of Google and IBM) and ion traps. But each of these technologies requires special conditions. For example, superconductor qubits work only at temperatures close to absolute zero (about -273 degrees Celsius). Bulky cryogenic systems are needed, which create an entire laboratory around one small cluster of qubits.

In addition, the qubits themselves are not perfect. They are prone to errors, quickly lose information and require correction. For stable operation of one logical qubit (i.e. one that can be really used for calculations) tens to hundreds of physical qubits are required. This means that to create a powerful quantum computer, not tens but millions of qubits are needed.

The challenges don’t end there. Here are just some of the most significant problems:

• Control and synchronisation: each cubit must be controlled precisely and quickly, not alone but in combination with others. Ultra-precise microwave signals and synchronisation systems are needed.
• Scalability: as the number of qubits increases, the number of cables, cooling systems, and controllers increases.
• Isolation from external noise: electromagnetic fields, vibrations, even the body heat of a person nearby can affect the quantum state. Almost perfect isolation is required.
• Quantum errors are the rule, not the exception. Therefore it is necessary to build correction systems into calculations, which makes the computer architecture even more complex.

These difficulties do not make quantum computing impossible, but they require huge investments and efforts. Large corporations, research centres and universities around the world are working to solve them, and progress is being made. However, the path to a truly universal quantum computer is very far away.

Mistakes That Cannot Be Ignored

The peculiarity of quantum systems is their extreme sensitivity to external factors. This is one of the main reasons why engineers face so many errors. Unlike classical computers, where a bit error is extremely rare and easily corrected, in quantum systems errors are almost constant.

There is a so-called decoherence – a process in which a qubit loses its quantum state. This can happen in a fraction of a millisecond. Even if the quantum state is stabilised, any operations can introduce inaccuracies.

There are two main types of errors:

• Errors in amplitude and phase when the cubit is “skewed” to one of the states;
• Read errors when the measurement result does not match the actual state of the qubit.

To work with such unreliable qubits, we have to use quantum error correction. But this is a complex and resource-intensive process. As already mentioned, one logical qubit requires tens or even hundreds of physical ones. This means that with current technologies even systems with several hundred qubits are not able to perform universal calculations.

Scientists are looking for workarounds: creating error-resistant algorithms, experimenting with new types of qubits (for example, topological ones), and exploring alternative methods of correction. But so far, the problem is reduced to how to make at least one qubit that works reliably and predictably, and then scale the solution.

Why Scientists Keep Working

Despite all the difficulties, interest in quantum computing is not fading. Moreover, the number of companies investing in this field and the number of patents related to quantum technologies are growing every year. Even at the current level of development, useful applications are already being created.

For example, quantum simulations are used in chemistry and materials science. Instead of long and costly simulations on classical supercomputers, quantum algorithms make it possible to simulate the behaviour of molecules more accurately and quickly. This is important when developing new drugs or materials.

Quantum algorithms also find application in logistics. For example, optimisation of routes, schedules, supply chains – all these are tasks that become difficult for classical systems when there is a large amount of data. Quantum approaches make it possible to find solutions faster and more efficiently.

It is important to understand: the path to a universal quantum computer may take decades. But already today the infrastructure is being formed – programming languages, simulators, cloud access platforms. Even if the user does not work with a real quantum processor yet, he can already learn, write algorithms and prepare for the future.