This article should outline to everyone what the term “quantum computer” means, how “qubits” work, or what the term “superposition” means. However, I want to say in advance that I am not an expert in quantum mechanics, quantum physics, quantum theory, nor am I actively involved in studying subatomic particles, although I hope that I understand the logical principles of these studies and technologies.

Beginner guide to quantum computing


Classic computers work with information using ones (1) and zeros (0). All data are interpreted in computers as a set of these values. One such state (one or zero) is called a bit.

One bit represents only one or zero, and more complex data consists of multiple bits. For example, “0100” is already a set of four bits that can be combined in various ways to carry different data.

Bits can also be used to perform basic operations, called bit operations, which take a set of bits and, for example, add, multiply, negate, and so on. A quantum computer does not use a bit as it is known in classic computers but uses a qubit.


Quantum-bit or abbreviated Qubit is the basic building block of a quantum computer consisting of, among others, a photon, an electron, and an atomic nucleus. It does not have the same rules as the classic bit.

Qubit does not have to be only in the state of one or zero, but also one and zero at the same time. This phenomenon is called quantum superposition. Qubit also uses one more feature, and that’s linking. Linking means that each Qubit affects the state of the mysteriously linked Qubit. I write “mysteriously” because we still don’t know how it all works.

We can explain the quantum superposition of Qubit, for example, by saying that Qubit can have a value of 0 at 40% and a value of 1 for the remaining 60%, but we do not know these percentages until we try to read the qubit value.

The Qubit value is determined by measuring, which can only get one of the two states 0 or 1. If we try to read the value of the Qubit, then its superposition collapses to one of the values ​​0 or 1 according to the state in which it was. No measurement is possible to get values ​​between 0 and 1. It’s like throwing coins until the coin lands, so you don’t know what fell to you. During the flight, the coin is in “superposition.” Another example of superposition could be the well-known Schrödinger cat experiment.

Beginner guide to quantum computing schrodiger cat

So what about a quantum computer?

A quantum computer is a type of computer that uses principles of quantum mechanics to perform certain types of computations much more efficiently than classical computers ever allow.

It uses its unique set of algorithms for calculations, which use the advantages of quantum mechanics, qubits, superposition, etc., to make calculations more efficient. One of the main algorithms is Shor’s algorithm, which is used to factorize large numbers, and Grover’s algorithm, for searching in an unstructured list.

For example, the search speed in an unstructured information sheet for classical computers is O (N). So if we have 100 rows in the list, then a classic computer needs a maximum of 100 operations to evaluate the search. Grover’s algorithm has a velocity O (√N). So if he worked on the same list of data using a quantum computer and applied Grover’s algorithm, then ten operations are enough to get the correct result. That’s not much, but if we imagine a sheet containing 1,000,000 lines, then a classical computer would have to go through just 1,000,000 records at its best, but a quantum computer only needs a maximum of 1,000 operations. If we imagine it on a scale of billions or more, we can already see some savings.

Unlike the classical computer, the quantum computer does not evaluate one value after another but evaluates all possible states (all million rows of a sheet) at once and then manipulates these states using quantum logic operations to achieve what we are based on will likely get the right answer. This approach isn’t perfect, but it makes the quantum computer an unimaginably more powerful machine. The quantum computer’s power grows much faster with each Qubit added than conventional computers.

The quantum computer also faces a lot of errors. So far, scientists have been able to keep the qubits in a certain state for only a fraction of a second. However, in many cases, qubits “crash” before the entire algorithm can be executed, leading to erroneous calculations. These errors can be corrected to some extent by adding more qubits to the system. Still, it uses so much additional computing power that it can even dampen the benefits of a quantum computer.

What are quantum computers for?

For less than 50 years, computers have improved according to Moore’s Law. Moore’s Law is a rule about the regular increase in computer computing power over time. But that rule must come to an end one day.

Quantum computers will take us a huge step forward in the evolution of computer technology. Although quantum computers will not be used for everyday use, they will have tremendous benefits in areas such as healthcare, physics, mathematics, chemistry, weather forecasting, security, space research, artificial intelligence, and machine learning.

In these areas, the computational power of technology is needed to run various simulations and calculations, in which quantum computer technology will help us. The theory even says that if used correctly, one quantum computer will be more powerful in the future than all the computing power on the planet. And now imagine if there isn’t just one.

Where is Quantum computing now?

Functional quantum computers that can perform some functions already exist, but we are still not approaching the performance we expect from the big things mentioned. For example, the most powerful quantum computer ever built is from Google and is at 75 qubits, along with IBM, whose computer is slightly more stable and has 50 qubits.

If we focus on numbers, then D-WAWE is next in line. This company created the so-called 2000-qubit system, a quantum computer that uses 2000 qubits in its system but has the disadvantage of great instability. As a result, the only usability is in the internal laboratories of companies such as Google or NASA. Interestingly, its price ranges over $ 15M. D-WAWE is working to maintain the line of Rose’s new Law, which states that it doubles the number of qubits used in their quantum computer each year, as mentioned earlier, to follow the Law of Moore.

Quantum computing terminology

  • Qubit – Quantum-bit or abbreviated Qubit is the basic building block of a quantum computer consisting of, among others, a photon, an electron, and an atomic nucleus.
  • Quantum coherence – deals with the idea that all objects have wave-like properties. If the wave nature of an object is split into two waves, the two waves can interact (coherently) to form a single state that is a superposition of their two states.
  • Quantum superposition – the fundamental principle of quantum mechanics. It states that any two or more quantum states can be added to form a new, valid quantum state.
  • Quantum entanglement – this is a physical phenomenon that occurs when groups of particles are generated, interact, or share spatial proximity such that the quantum state of anyone particle cannot be described independently of the state of the other particles.

Future with quantum computers

The quantum computer will certainly not turn the world upside down, but its introduction into practice will cause many fundamental changes. For example, today’s cryptographic codes used in money transactions on the internet will become unusable because quantum computers crack them like nuts.

Data centers will undoubtedly undergo a radical transformation, with quantum computers providing lightning-fast records searches, especially in unsorted databases. The further progression of the miniaturization of integrated circuits runs up against the laws of physics, and a shift in technology to the subatomic level seems inevitable. Mastering quantum mechanics, however, will be neither quick nor easy.

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