What is Quantum Computing?

Is quantum computing a reality or mere science fiction? Do quantum computers already exist or are they still in the realm of speculation? Will quantum computers substitute general-purpose computers? How far are we from witnessing their commercial production, if it ever happens?

In this blog post, we explore facts, myths, and concerns surrounding the advent of a new technological revolution.

What is quantum computing?

Quantum computing is a field in computer science that draws upon the principles of quantum theory. Traditional computers rely on manipulating electrical impulses represented by binary digits (1s and 0s) to store and process information. (In binary code, the digit 1 stands for an “on” state or a high voltage, while the digit 0 signifies an “off” state or a low voltage.) Quantum computing uses the properties of subatomic particles such as electrons or photons. Quantum bits, or qubits can exist in multiple states simultaneously. Check out this video to find out how this paradox works.

Quantum circuit

This feature, known as superposition, allows qubits to represent both 1 and 0 simultaneously. Consequently, quantum computers can perform computations on an unparalleled scale that would take regular computers millions of years by cleverly manipulating and using the interference between their quantum states.

The concept of quantum superposition suggests that when a physical system has multiple potential configurations or arrangements of particles or fields, its most comprehensive state can be described as a combination of all these possibilities. In this combined state, the proportion of each configuration is determined by a complex number.

In contrast, classical computers are limited by their reliance on binary encoding, which restricts their processing capabilities, particularly when facing complex problems.

Watch this video for a more comprehensive explanation of quantum computation.

The described working principles of quantum computers led to the misconception that quantum computers can perform calculations at orders of magnitude faster than the computers we now use and that they are more powerful and superior in functionality. However, scientists mention that there are many tasks in which quantum computers do not have any significant advantage over classical computers unless the algorithm being used exploits quantum parallelism. In the following discussion, we will evaluate the potential of quantum computing and determine the cases in which quantum computers demonstrate unbeatable results, and when they fail.

What is the difference between quantum computers and supercomputers?

Quantum computers and supercomputers have different ways of processing information, each with its own strengths and limitations.

In quantum computing, the building block is the qubit, or quantum bit. Supercomputers use traditional bits and parallel processing with multiple processors to handle different parts of a problem at once. The difference in computation in quantum computers and supercomputers is grounded on the idea that the former use continuous variables (CV) as their base element, while the latter employ discrete values (DV). Read a detailed explanation of approaches to working with DV and CV here.

Quantum computers are great at solving certain problems faster, such as optimization and simulation tasks like drug design or supply chain optimization. Supercomputers excel at data-intensive tasks, like analyzing large datasets, pattern recognition, or modeling complex systems commonly used in weather forecasting, scientific research, and military simulations.

However, both quantum computers and supercomputers have their barriers.

Quantum computers limitations

  • Fragility: Quantum computers are susceptible to their environment, including temperature changes, and can easily be disrupted by noise and vibrations. Any disturbance can cause the system to lose coherence, resulting in calculation errors.

  • Error correction: Due to their sensitivity to noise, quantum computers require error correction. However, it involves additional hardware and software that can increase the complexity and cost of the system.

  • Limited qubits: Quantum computers have a limited number of qubits, which restricts their computational power. While researchers are working to increase the number of qubits, it is still a major challenge.

  • Limited applicability: Quantum computers have shown promise in simulating quantum systems, factoring large integers, and optimizing certain search algorithms. Currently, they are inferior in efficiency compared to the supercomputers working with general-purpose computing tasks such as word processing or browsing the internet.

Quantum computers are still in the early stages of development. They are also very expensive to build and maintain, requiring specialized expertise. Supercomputers, while also costly, are more accessible and easier to manufacture. They are generally more reliable and have longer lifespans compared to quantum computers.

What are the principles behind quantum computers?

Quantum computers are based on the principles of quantum mechanics, namely superposition, entanglement, and decoherence. Let’s look at each of these concepts.


In quantum mechanics, superposition is the ability to combine multiple quantum states, similarly to how classical physics deals with the addition of waves. By adding two or more quantum states, you can obtain a new valid quantum state. Conversely, any quantum state can be represented as a combination of two or more different states. The superposition of qubits in quantum computers enables them to process numerous operations concurrently.


Quantum entanglement occurs when two systems become intricately connected, allowing for immediate information transfer between them, regardless of their spatial separation. In quantum processors, measuring one particle enables you to make a conclusion about another particle. For example, if one qubit is observed to spin upwards, its entangled partner will always be found spinning downwards, and vice versa.

Through entanglement, qubits can form connections with other qubits, which greatly enhances their computational power. However, when a quantum state is measured, its wave function collapses, revealing either a zero or a one. We have been familiar with it for quite some time through simulations of quantum computers using conventional CPUs. However, these simulations can only be performed for a small number of qubits. In practice, if you were to attempt using the IBM API for this purpose, you would consistently encounter ‘unclean readings.’ Resolving this issue is one of the many aspects that scientists are currently working on.


Decoherence is the deterioration or loss of a qubit’s quantum state due to factors like radiation. To build a quantum computer, it’s important to overcome this challenge. Engineers design specialized components to prolong the coherence of the quantum state. This involves constructing protective structures that shield the qubits from external fields, reducing the negative effects of decoherence.

This video explains the concepts of superposition, entanglement and decoherence more in detail:

Do full-fledged quantum computers already exist?

In 1998, I. Chuang from the Los Alamos National Laboratory, M. Kubinec from the University of California, and N. Gershenfeld from the Massachusetts Institute of Technology achieved a significant milestone by creating the first 2-qubit quantum computer. However, even in the year 2023, there continues to be ongoing debates regarding whether fully functional quantum computers have truly become our present reality.

According to researchers, the answer depends on how we define quantum computers and the specific problems we expect them to solve. Experts point out that the lack of a demonstrated working logical qubit on any experimental platform adds complexity to estimating progress in this field. These estimates are often based on noise models, which initially align with experimental findings. However, as experiments scale up, deficiencies in these models become apparent, leading to frequent updates and rapidly changing numbers.

In summary, the readiness of quantum computers for practical applications is still subject to ongoing research and refinement, with various factors contributing to the uncertainty surrounding their development.

What is quantum computer

What is the architecture of the quantum computer?

The architecture of a quantum computer consists of several planes:

  • The “quantum data plane” houses the qubits.
  • The “control and measurement plane” executes operations and measurements on the qubits as needed.
  • The “control processor plane” determines the sequence of operations and measurements the algorithm requires, possibly utilizing measurement results to guide subsequent quantum operations.
  • The “host processor” is a classical computer that manages network access, extensive storage, and graphical user interfaces (GUI).
Quantum computer architecture

Which companies are developing quantum computers?

In the race to develop quantum computers, a competition for supremacy is unfolding. While it’s hard to identify a clear frontrunner these five contenders stand out as frontrunners.


IBM is among the pioneers in the quantum computing race so far.

In 2019, the company introduced the IBM Quantum System One – a fully integrated quantum computing system developed for commercial applications. It supports multiple processors, including the Falcon processor with 27 qubits, the Hummingbird processor with 65 qubits, and the Eagle processor with an impressive 127 qubits.

In November 2022, the IBM Quantum System Two was unveiled. This modular and expandable system was designed as a fundamental component of the quantum-centric supercomputer. By integrating classical compute resources and efficient cooling systems, it has the capacity to accommodate large processors and future architectures, including modular devices.


Microsoft has successfully developed all the essential components necessary to realize a topological qubit—a novel type of qubit that promises superior speed, compactness, and reliability compared to other qubit designs, competing with IBM for leadership in quantum computer development. As this technology progresses, topological qubits will be the foundation for Microsoft’s fully scalable and highly secure next-generation quantum computer.

Moreover, Microsoft’s Azure cloud platform provides a remarkable advantage by granting companies access to quantum resources without the burdensome expenses and infrastructure costs typically associated with such endeavors. Through Azure, users can conveniently access resources from various providers, including QCI, Honeywell, Toshiba, IONQ, and 1Qloud.


The Google Quantum AI lab in Santa Barbara is dedicated to creating a quantum computer that can solve real-world challenges, thereby establishing Google as one of the top three quantum computer developers. Their goal is to develop practical applications that align with their long-term objective of building a universal quantum computer with error-correction capabilities. Google aims to bridge the gap between theory and real-world impact, making quantum advancements accessible and beneficial to various industries.


D-Wave’s quantum computers utilize a specialized technique called quantum annealing, specifically designed for optimization problems. When users input a problem into the system, the quantum processing unit considers all possible configurations at once, generating calculations corresponding to the most optimal arrangement of qubits. These calculations provide the best possible solutions, resulting in higher-quality results, particularly for large-scale problems. D-Wave systems are employed by some of the world’s biggest companies, including Google, NASA Ames, Oak Ridge National Laboratory, and Volkswagen.


Amazon is actively developing the infrastructure for quantum computing. The company recently founded the AWS Centre for Quantum Networking, a central hub for research on quantum networking. Furthermore, through Amazon Braket, developers gain access to quantum computers from leading providers like IonQ, Oxford Quantum Circuits, Rigetti, and D-Wave. Amazon also runs the AWS Center for Quantum Computing in Pasadena, California, and operates the Amazon Quantum Solutions Lab. These initiatives aim to promote advancements and solutions in quantum computing, making it more accessible and practical for users.

There are other companies and research institutes involved in quantum computing, find out more in the video:

What is the current state of quantum computing?

Quantum computers are still in an early stage called the Noisy Intermediate Scale Quantum (NISQ) era. They have limitations in terms of the number of qubits and their sensitivity to errors caused by the environment. However, despite these limitations, NISQ devices show the potential of quantum computing.

Researchers are improving NISQ computers to reach the next phase, Fault Tolerant Quantum Computing (FTQC). FTQC aims to reduce errors by using redundancy, but it requires more physical qubits.

The transition from NISQ to FTQC will take time, and quantum computers will gradually solve a broader range of problems. In the meantime, NISQ systems are valuable for businesses interested in adopting quantum computing. To save costs, it’s practical to start experimenting with algorithms on classical simulators before moving to quantum hardware.

It’s important to note that quantum computers are unlikely to replace classical computers completely. Business solutions will involve a combination of classical and quantum hardware, with quantum processors handling specific parts of the problem.

What are the challenges of developing a quantum computer?

Advancements in qubit technologies have led to the introduction of small gate-based quantum computers. However, significant challenges remain, which are currently the focus of numerous developers and researchers. Some of the problems that are yet to be solved are listed below:

Quantum decoherence: Decoherence occurs when the delicate quantum states that encode information interact with the surrounding environment, causing the loss of quantum properties. It poses a significant challenge in maintaining the stability of qubits.

Qubit reliability and scalability: Qubits are fragile and susceptible to errors. Developing qubits that are both highly reliable and scalable is a significant challenge. Researchers are exploring various physical implementations, such as superconducting circuits, trapped ions, topological qubits, and others, to achieve more stable and scalable qubit architectures.

Quantum error correction: Error correction is crucial in quantum computing due to the inherent susceptibility of qubits to noise and errors. Today, systems are limited by two-qubit gate error rates above the surface code threshold. Error rates need to be at least an order of magnitude better. Improving the physical error rate to 10^-4 decreases the logical error rate to 10^-18. Quantum error correction techniques aim to protect the fragile quantum states against decoherence and other errors.

Quantum gate operations: Developing and implementing a universal set of quantum gates that are accurate and efficient. The control and manipulation of qubits at the quantum level require precise and stable control over physical systems.

Hardware and infrastructure: Building a quantum computer requires sophisticated infrastructure with extreme environmental conditions, such as ultra-low temperatures, low electromagnetic interference, and highly stable experimental setups.

Software and algorithms: Quantum computing requires the development of new efficient quantum algorithms, optimizing quantum circuits and software tools tailored to quantum systems.

When will quantum computers arrive?

In the coming years, big players in quantum computing, alongside start-ups, will be gradually increasing the qubit capacity and reducing qubit error rates of their computers. However, progress is likely to be slow. McKinsey projects that by 2030, around 5,000 operational quantum computers will be available. Developing the necessary hardware and software may take until 2035 or even later.

Companies developing quantum computers

Nonetheless, certain businesses will begin to derive value from quantum computing well before this timeframe. Initially, these businesses will have access to quantum services through cloud-based platforms provided by the companies they currently work with. Several major computing companies have already announced their forthcoming quantum cloud offerings.

How will quantum computing change the world?

Thanks to its ability to solve complex optimization problems, quantum computing may have far-reaching implications across many industries. While still in its early stages, this technology holds immense possibilities for the future.


One of the most notable advancements brought about by quantum computing is its ability to transform cybersecurity and data encryption. Today, data security heavily relies on encryption keys for secure transmission. However, hackers can replicate these keys, thus gaining unauthorized access to sensitive information. By employing the principles of probability theory, quantum machines make processed information inherently immune to duplication or replication.

In quantum computing and physics, data processing is remarkably secure. Attempts to unlawfully access data in the quantum-backed security system result in the dissolution of the original data composite, rendering it unhackable. Although it may sound like science fiction, data transmission in the quantum world resembles teleportation. Altering one particle affects the other through entanglement. Therefore, unauthorized access of data would necessitate breaking the fundamental rules of quantum physics.

Drug development

With the advancements in quantum mechanics, there has been a significant improvement in our understanding of atomic interactions. Moreover, the enhanced processing power offered by quantum computers enables researchers to conduct experiments on molecules and particles at an unprecedented pace, accelerating the search for treatments for presently incurable conditions.


The scientific community is enthusiastic about the potential of quantum computers in modeling intricate quantum processes fundamental to chemical reactions, which is still a challenge even for the most powerful supercomputers.


Experts are actively exploring the implications of quantum computing in diverse domains, such as machine learning, to unveil novel patterns in nature and advance the capabilities of artificial intelligence. Quantum computers can enhance data analysis capabilities. Their computational power can expedite complex data processing tasks, leading to more accurate and efficient pattern recognition, classification, and data clustering. This can benefit various domains, including image and speech recognition, fraud detection, and natural language processing.

Quantum computers can also enable faster model training, parameter optimization, and improved algorithmic performance. This can lead to advancements in fields like predictive modeling, recommendation systems, and autonomous decision-making.

Financial automation

Quantum computing applications offer significant advantages to businesses, allowing them to perform investment calculations and forecast stock market trends quickly and efficiently. They can also aid in identifying potential risks and developing strategies to mitigate them, as well as conducting computationally intensive simulations. The remarkable speed of quantum computers enables them to carry out these operations exponentially faster than traditional computing systems.

Fraud detection

Industries such as healthcare, banking, and marketing require reliable solutions for detecting fraud through entity relationships and data patterns. Quantum computing can enhance data modeling, offering a resource-efficient method for neural network training and improving the effectiveness of fraud detection rates.

Traffic optimization

Quantum computing applications focused on data extraction and pattern analysis can help improve organic traffic for businesses, enabling marketing firms to offer precise and quick services to a targeted audience.

Logistics optimization

It’s natural for businesses to seek a system that provides improved data analysis and reliable performance modeling to enhance supply chain management. Subsequently, the implementation of quantum computing in logistics would offer robust computational solutions.

Industry Applications
FinTech Algorithmic trading, fraud detection, portfolio optimization, loans scoring
Manufacturing Workforce and job scheduling, supply chain and inventory optimization, demand prediction
Transportation Route optimization, traffic management, vehicle loading and dispatch
Healthcare Drug discovery, gene sequencing and annotation, molecular simulation, organ exchange

What are the concerns about quantum computing?

Previous technology advancements highlighted the importance of establishing governance and standards early on. The impact of quantum technology remains uncertain, making necessary the development of responsible deployment policies and equitable access. Overall, it is crucial to focus on societal impact and unintended consequences.

Cyber security

According to the US National Institute of Standards and Technology (NIST), by 2029, quantum computers will be able to break current public key infrastructure, including 128-bit AES encryption. This encryption is currently used to protect sensitive information transmitted over the Internet.

The need to address this encryption challenge drives the demand for large-scale quantum computers with 10,000 or more qubits. These machines could be employed for intelligence operations, specifically decrypting data with relatively low levels of encryption.

DNN black box problem

If quantum computing is used in machine learning, it could create a big problem called the “ultimate black box problem.” Deep neural networks are already hard to understand, and with quantum machine learning, it becomes even harder to evaluate them and understand how they make decisions.

Warfare vulnerability

Quantum technology can address complex societal challenges, but it can also be used maliciously by nation-states during warfare. If a military force possesses quantum computing capabilities while its opponent does not, the information imbalance may leave the latter unable to protect its assets and vulnerable to strategic disadvantages.

Societal risks

The widespread adoption of quantum computing poses a significant societal risk: the exponential expansion of the digital divide. Due to the high costs associated with quantum computing, only the wealthiest individuals and organizations will likely have access to its immense power. This situation could perpetuate and amplify existing disparities between privileged and underprivileged groups, potentially leaving those unable to afford quantum computing services at a disadvantage and further behind in various aspects of life.

Limited helium supply

Quantum technology depends on cooling particles with helium to maintain their stability. However, the limited supply and high cost of helium present two potential risks. Firstly, companies must ensure a reliable source of helium to keep their equipment running. Secondly, there is a risk of a concentration of capabilities in the hands of a few operators, leading to a potential imbalance of power and access to quantum technology.

The future is happening now

The quantum revolution is no longer a distant concept; it is happening right now, although on a smaller scale. Governments, tech giants, and private investors are engaged in a race to invest in research and development of quantum physics, hardware, and software. Businesses start considering quantum computing in their projections and initiate preparations for the impending large-scale transformation.

With the integration of quantum computing across different disciplines, we can even come closer to understanding black holes and, who knows, maybe explore constellations millions of light years away.

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