There is no doubt computer science advances at high speed. Each year we can find new, more compact, and powerful microprocessors – the part of the computers that makes the calculations – which allows faster handling of a large amount of information. For example, current mobile phones’ microprocessors are more powerful than the supercomputers of the nineties.
However, a physical barrier looms over the improvement of microprocessors: the difficulty in reducing the size of transistors. Transistors are like the “atoms” of a microprocessor. Nowadays, they have a size between 7-10 nanometers (one millionth of a millimeter in size). In the coming years this size will be reduced between 1 and 5 nanometers, but what would happen if we cannot continue reducing the size of microprocessors? Could we really go beyond that physical barrier that semiconductor materials – such as silicon – and computer science offer today?
This is where quantum computing comes in, promising to revolutionize traditional computational science and large-scale data processing. Although it was in the early 50s when we first heard about quantum computing, the development of the first quantum computers happened approximately in the year 2015, starting a new era in computer science. Quantum computing tries to overcome the limits of traditional computational science, creating computers which will be able to solve – in few seconds – complex problems that would take millions of years to solve by current computers.
Quantum computing is based on quantum physics, which studies the behavior of subatomic particles. The properties of these particles are quantized. That means, they take discrete values. In current computing we can work with two states, zeros (0) and ones (1). In quantum computing values not only can be treated in one or another state, but they also can be in a linear combination of them, what is called a superposition of states. Also, these states are connected! or, as physicists say, entangled.
Current computers store the information in bits, which have the status of 0 or 1. In quantum computing, the same information would be stored in the form of Qbit or Qubit (quantum bit). These quantum bits can have not only the two states (0 or 1) but they can have any intermediate state. Moreover, thanks to entanglement, the change in one state affects the rest. That is the reason why quantum computing is more efficient solving problems, as every possible solution can be tested at the same time. One example could be the encryption systems that are used today to protect communications on the internet. This fact is based on the idea of factoring large numbers. Finding these factorized numbers would require centuries of computing with the current supercomputers. However, there are already theoretical algorithms in quantum computing that would be able to solve this problem much more quickly. Once the first quantum computer begins to work, these current encryption systems would no longer be an effective way to protect personal data, with the impact that would have on our daily lives.
Although quantum computing is advancing very fast, current quantum computers are simple prototypes that require extremely stable environments to work efficiently and accurately. For example, a quantum computer needs to work at a temperature of -273º Celsius to maintain the stability of the states of the mentioned quantum bits. On the other hand, current prototypes are not yet capable of executing all types of existing algorithms. An algorithm describes the instructions that a computer must execute to solve a problem. For quantum computers, the instructions of “classical” algorithms must be rewritten so they (the quantum computers) can understand this information. However, there is still a long way to go to be able to rewrite all those equivalent quantum algorithms.
In conclusion, we can say that an extensive and complex area of research opens up. This will promise an unprecedented impact on humanity. But we must not forget that we are still far from having commercial quantum computers. In fact, in case these computers become a reality today, quantum computers would be more like a complement to current computers to solve certain types of problems than an alternative for computer’s technology.