Quantum computers are based on qubits, which perform far more complex and powerful operations than bits, and can efficiently solve problems such as prime factorisation. However, their sensitivity to the external environment and lack of practical algorithms have hindered their commercialisation.

About quantum computers

A few years ago, the world’s first commercially available quantum computer was announced by D-Wave Systems, Inc. Since then, it has become even more famous, with Lockheed Martin, Google, the world’s leading internet company, and the National Aeronautics and Space Administration (NASA) using D-Wave’s computers. But what is it about quantum computers that has attracted such big names and media attention? Let’s take a look at the principles of quantum computers and see where we stand today.
The development of quantum computers has its roots in the study of quantum mechanics, which began in the late 20th century. Quantum mechanics is a theory that goes beyond the limits of classical physics to explain the behaviour of particles in the microscopic world. This led to the exploration of the potential for breakthroughs in information processing technology, and quantum computers emerged as one of the outcomes. The fundamental reason for the development of quantum computers is the introduction of the principles of quantum mechanics to overcome the physical and computational limitations of conventional computers. In modern science and technology, quantum computers have the potential to become more than just a computing machine, but a key technology in various fields such as physics, cryptography, and chemical simulation.
To understand quantum computers, we need to look at how they differ from classical computers. Let’s take a look at the differences, starting with the units of information and ending with how they are calculated.

Units of information: bits and qubits

Let’s start with the units of information. While classical computers use bits, quantum computers use qubits as the unit of information. A bit can only represent one of two values: 0 or 1. However, a qubit exists as a superposition of zeros and ones. By nested, we don’t mean that it has a value somewhere between 0 and 1, but rather that it has the potential to be either 0 or 1 when measured. In other words, unlike a bit, which is fixed to one value, a qubit has two possibilities at the same time. Furthermore, unlike bits, qubits have many different states, and the state of a qubit determines the probability of a 0 or 1 when measured.
These properties of qubits make quantum computers work in a fundamentally different way than classical computers. To understand this, let’s take a look at quantum logic operations.

Quantum logic operations vs. classical operations

Classical computers are composed of operations with bits as inputs and outputs. For example, the AND operation takes two inputs and gives one output, which is 1 if both inputs are 1 and 0 otherwise. There are several other basic operations of this type, and combinations of them are the basis of computers.
A quantum computer, on the other hand, consists of operations with qubits as inputs and outputs. The result of the operation changes the probability of each qubit being a 0 or a 1. For example, the CNOT operation looks like a similar operation to a classical computer, but the output is different because of the superposition of qubits. For example, if two qubits are given as input, each of which has the same probability of being both 0 and 1, the output can be varied to reflect this possibility.
Quantum logic operations become more complex as the number of qubits increases. When three or more qubits are involved in an operation, the number of cases grows exponentially, and quantum computers treat these operations as a single operation. For example, a computing device that processes 64 qubits can consider 1845 different states simultaneously. This means that its computational power is enormous when compared to a classical computer.

The computational power of quantum computers

This characteristic makes quantum computers extremely powerful for certain problems. Two of the most prominent examples are Shor’s Algorithm and Grover’s Algorithm. Shor’s Algorithm can efficiently perform prime factorisation, which can pose a serious threat to currently popular encryption methods. Grover’s Algorithm is a fast data search algorithm that can find data that meets specified criteria very quickly. These algorithms are prime examples of how quantum computers can solve problems that are difficult for classical electronic computers to handle.
Nevertheless, quantum computers still face some significant challenges on the road to commercialisation.

Obstacles to quantum computers

The first problem is the difficulty of making quantum computers work reliably. Quantum computers are extremely sensitive to external stimuli. Due to the nature of quantum mechanics, any external influence during a calculation can lead to completely different results than expected. For example, if a qubit interacts with the external environment, its state can quickly collapse, leading to errors. To solve this problem, a technique that reliably controls and protects qubits is essential, but it is not easy to fully implement with current technology.
The second problem is that efficient algorithms that harness the computational power of quantum computers have not yet been fully developed. In addition to Shor’s Algorithm and Grover’s Algorithm, we need quantum algorithms that can solve a wide range of problems, and there are currently very limited algorithms available. Researchers continue to work on new quantum algorithms to solve this problem.

Future possibilities of quantum computers

Although quantum computers are still in their infancy, the possibilities for their development are endless. Traditional electronic computers are limited to getting smaller and faster. Quantum computers, on the other hand, have yet to reach their limits, and their potential is limitless, especially when it comes to quickly processing huge amounts of data or solving complex problems.
In his book ‘ Programming the Universe,’ Seth Lloyd, a leading expert in quantum mechanics and quantum computers, explains that the universe stores and processes information like a quantum computer, and that it is impossible to distinguish between the universe and a quantum computer. According to his argument, quantum computers can be tools that harness the computational laws of the universe itself. This means that quantum computers are consistent with the fundamental workings of the universe.
Therefore, the development of quantum computers will ultimately be an important step towards understanding the nature of the universe and, in doing so, reaching levels of computational power that we cannot imagine. If, in the near future, we are able to put quantum computers to practical use, it will mark a new level of technological innovation for humanity.