A quantum computer is a computing device built upon the principles of quantum mechanics. The theoretical performance of quantum computers exceeds that of traditional systems based on semiconductor processors by a long way.
Bits and qubits
Quantum computers operate with qubits (quantum bits) — the basic quantum units of information storage. From a physics point of view, a qubit is an elementary particle (like an electron), and its value is derived from one of the physical properties of this particle.
Unlike classical bits, which can only have one of two values — 1 or 0, qubits are in a superposition of these two values during calculations (until their final state is measured); that is, they (qubits) can take either of them with a certain degree of probability. In addition, each qubit constantly interacts with other qubits in the quantum system in such a way that their states influence each other.
Due to the peculiarities of qubits, quantum computers can, in theory, solve tasks that are way beyond the power of ordinary computers. At the same time, quantum systems will most likely never be able to cope with some tasks that conventional computers solve so well.
Possible applications of quantum computing
Among the tasks in which quantum computers may outperform the ordinary ones are:
- Creating new cryptographic algorithms
- Quick searches of databases
- Modeling molecular systems
- Resource-intensive scientific research
Problems with quantum computing
Despite the enormous theoretical computational capabilities of quantum computers, their development in practice is progressing rather slowly. This is due to a number of issues that researchers have not yet completely solved.
- Sensitivity to the environment. External factors impact the state of individual qubits and the quantum system as a whole. The slightest change in temperature or air pressure, or even a photon whizzing past, can destabilize it. To ensure the stable operation of quantum computers, they are housed in cryogenic refrigerators isolated from the external environment, inside which the temperature is kept close to absolute zero. Shielding and cooling systems are expensive and take up a lot of space.
- Computational errors. Quantum calculations are probabilistic; that is, not always correct. And, as with traditional computers, failures and errors can occur. The more complex and powerful the system, the more prone it is to errors.
- Lack of standards. Current quantum computers are implemented differently, so there is no universal software to work with them. This was a problem for traditional computers, too, in the early stages of their development.