Contemporary computers represent one of humanity's most advanced technological achievements, assisting in predicting natural phenomena, training artificial intelligence, simulating drugs, financial management, and being present in almost every aspect of daily life.
However, certain problems persist as challenges even for the planet's most powerful supercomputers. In specific scenarios, the magnitude of the required calculations can take years to resolve, rendering the answer useless.
Faced with this limit, researchers began investigating a different approach: instead of seeking faster machines, would it be feasible to create a new computing methodology? It was from this inquiry that quantum computing emerged, a field of study that explores the principles of quantum mechanics to solve problems beyond the capacity of current computers.
According to Marcelo Finger, a Computer Science professor at the University of São Paulo (USP), the initial concept dates back to the last century, proposed by physicist Richard Feynman, and is based on the concept of superposition.
The basic premise lies in superposition: a particle can coexist in multiple states simultaneously, only one of which is selected at the moment of measurement. The intention was to execute several computational operations at the same time and subsequently separate them using a specific mechanism, resulting in a drastic increase in processing speed.
View on the application of quantum computing
Only in recent years has quantum computing begun to gain relevance outside academia. Ivan Oliveira, coordinator of the Quantum Technologies Laboratory (QuantumTec) at the Brazilian Center for Physical Research (CBPF), explains that the proposal consists of using phenomena from the quantum domain, observed under very specific material conditions, to accelerate certain computational processes. The growth of prototypes and increased investment have driven interest in this technology, which promises to expand the limits of traditional computing.
To understand its uniqueness, it is crucial first to understand what differentiates it from the computing used today. Despite all the computational evolution of recent decades, one fundamental characteristic has remained unchanged since the dawn of electronics: all process data using the same basic logic.
This logic is established through bits, the smallest unit of classical computation, where each bit can assume only two values: 0 or 1. Although it seems simple, it is the combination of billions of these tiny states that enables the representation of text, images, videos, music, and any digital data.
For this reason, even if a smartphone and a supercomputer have distinct capabilities, both operate under the same principle. The difference lies in the speed of processing and the amount of calculations they can perform.
Quantum computing breaks with this structure. Instead of bits, it employs a different unit of information: the qubit. As pointed out by Ivan Oliveira, coordinator of the Quantum Technologies Laboratory (QuantumTec) at the Brazilian Center for Physical Research (CBPF), the qubit can be seen as the analogue of the transistor in classical computing, but with the ability to simultaneously represent the states zero and one.
This characteristic derives from the phenomenon of superposition, a pillar of quantum computing. This raises the question of how something can exist in more than one state at the same time. A useful analogy is to compare it to tossing a coin: when it lands, it is heads or tails, mutually exclusive states. However, if this coin were quantum, it could manifest a physical state that is both heads and tails at the same time, explaining the inherent parallelism of a quantum computer.
Limits and Potential Applications
Thus, the discussion shifts from how the quantum computer works to what types of problems it can effectively impact. Understanding how it works is only half the battle; the other half is knowing in what situations this technology offers an advantage over conventional systems.
Contrary to what might be assumed, a quantum computer was not designed to replace laptops, cell phones, or servers. For most daily activities—such as web browsing, video viewing, document editing, or sending messages—conventional devices remain the best choice.
According to Ivan Oliveira, quantum computers will need to integrate into a larger computing infrastructure, collaborating with traditional systems. They will be responsible only for phases of problems that are intractable for classical computing, while the rest will be handled by current computers. The researcher emphasizes that 'heavy classical computing' is necessary to manage the quantum computer, run the algorithms, and interpret the results.
In this context of challenges, researchers like Pamela Bezerra identify highly promising applications. Quantum computing aims to solve extremely complex problems, those that even the best servers, even with parallel algorithms, cannot solve in a timely manner, especially when the volume of data and variables increases. It also offers the chance to simulate nature with greater precision, using the properties of quantum mechanics to perform chemical simulations of atoms and molecules.
The simulation of chemical reactions and molecules is a notable example. Understanding the behavior of these structures can accelerate research in the development of new medicines, materials, fertilizers, and other chemical compounds, in addition to boosting various industries.
Marcelo Finger indicated that areas requiring great processing power, such as artificial intelligence, protein research, drug creation, and particle physics, are the ones that can benefit most from quantum computing. Other applications include optimization problems, where logistics, transport, electrical grids, and financial institutions deal with millions of combinations, potentially finding more efficient solutions, saving time, energy, and resources.
Digital security is also closely monitored by the scientific community. Current encryption methods may require adaptations for a scenario where quantum computers execute calculations with greater efficiency. Simultaneously, quantum mechanics itself paves the way for new forms of secure communication.
Scientific and Technological Challenges
These examples illustrate the great interest in quantum computing, but for now, they represent only possibilities. Although recent advances have been relevant, transforming this potential into accessible applications depends on overcoming central scientific and technological obstacles in the research.
If the prospects are so encouraging, why are quantum computers not yet used on a large scale? The answer lies in one of the biggest hurdles in the field: building an operational quantum computer is considerably more complex than imagining its uses.
For quantum phenomena to be observed and applied, processors must operate at temperatures close to absolute zero. Thus, Marcelo Finger compares a quantum computer to 'a large refrigerator.' Even under these extreme conditions, the systems suffer from interference that harms the functioning of the qubits and complicates calculations.
Qubits are extremely sensitive to the environment. Temperature fluctuations, vibrations, and electromagnetic fields can introduce errors during processing, making stability one of the biggest challenges in quantum computing. For Ivan Oliveira, the 'Holy Grail of quantum computing' is controlling these errors. Although every computational process has flaws, ways to correct them in quantum machines are still being sought.
Overcoming this challenge is what distinguishes experimental quantum computers from future machines capable of solving real problems. Pamela Bezerra states that quantum computing has transcended the status of mere theory, reaching an intermediate stage of development. Current equipment demonstrates proof of concept and shows continuous improvements in hardware, but still lacks the necessary capacity to solve real-scale problems. It is expected that in the coming years, these systems will progressively evolve toward commercial and practical applications.
This is why existing quantum computers are mostly used in experiments and research. Despite significant advances, converting these machines into reliable problem-solving tools requires overcoming crucial barriers. This scenario also justifies the caution of the scientific community regarding announcements of new processors or performance records; each advance is an important step, but it does not guarantee readiness for large-scale use.
The obstacles to creating a functional quantum computer are immense. Nevertheless, governments, universities, and large global technology corporations continue to invest billions of dollars in this sector. Quantum computing has ceased to be a purely academic topic to become a strategic technology, with the potential to generate scientific, industrial, and economic advancements in the coming decades. Ivan Oliveira summarizes that there is a 'real technological race' for quantum computers capable of solving problems intractable for current computing, and much of this investment is concentrated in the Northern Hemisphere.
This dispute is not limited to just increasing the number of qubits. The focus is on developing machines that execute complex calculations in a stable, reliable, and useful manner for real applications. Pamela Bezerra highlighted that the last few years have brought progress in both hardware and software: processors have gained more qubits and greater stability, while new programming languages, libraries, and platforms have expanded research possibilities, despite persistent limitations in processing and memory.
