What Is Quantum Computing and How Does It Work?

9 January 2025
7 min read
Hayk Tepanyan
Co-founder & CTO
Quantum computing use cases

Quantum computing is one of the biggest topics in technology today—right up there with AI and renewable energy. It’s tangible proof that the future is now. This game-changing field is even compelling some tech giants to join the revolution. Industries and governments around the world are racing to make the most of the technology, with major companies like IBM and Google investing millions in quantum computing research and development. 

The motive behind this rat race is simple: there are complex problems that only quantum computing can solve. These include drug discovery, materials research, and financial portfolio optimization—just to name a few. With such massive potential, billions of dollars are pouring into quantum computing as more and more companies are considering it to be the future of computational technology. 

Now, the same principles that make quantum computing so powerful also make it an incredibly complex field by nature. Concepts like superposition, entanglement, and decoherence can seem intimidating. After all, something that has the potential to change the status quo will always come with some degree of confusion. Then again, there are ways to make these ideas easier for everyone to grasp so that the technology is more accessible to those who want to benefit from it. 

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How Does Quantum Computing Work?

Quantum computing uses the principles of quantum mechanics to process information—useful for tasks like optimization, simulations, and cryptography. Instead of classical bits, quantum computers use qubits, which can exist in multiple states at the same time. This allows quantum computers to perform a number of calculations simultaneously, solving problems much faster than traditional computers.

Superposition

Superposition allows qubits to exist in multiple states—0, 1, or both—at once, unlike classical bits, which are restricted to one state. This allows quantum computers to process large combinations of inputs simultaneously, boosting their computational power. With the help of superposition, quantum systems can explore multiple possibilities at the same time, exponentially minimizing the time it takes to find solutions for complex problems.

The introduction of multidimensional states makes it possible for binary-based systems to evaluate multiple combinations of 0s and 1s simultaneously instead of one combination at a time. This accelerates tasks like searching large datasets, solving equations, or simulating physical systems.

Entanglement

Entanglement links qubits in a way that the state of one directly affects the other, even if they are physically separated. This makes it possible for quantum computers to perform computations across qubits, boosting processing power and efficiency. Since the collective state of entangled qubits can detect and fix errors without direct measurement, entanglement also improves quantum error correction.

Entanglement can help solve large-scale problems and improve cryptographic systems. In the future, it might support quantum networks for instant communication over large distances, taking the exchange of data to a whole new level.

Quantum Interference

Quantum interference happens when the probabilities of qubit states combine in constructive or destructive ways, amplifying correct results and canceling out errors. Quantum algorithms use this phenomenon to guide computations toward the best solutions. In practice, quantum interference allows quantum systems to explore complex solution spaces more efficiently. This leads to advancements in quantum computing applications like optimization, pattern recognition, and simulation.

What Makes a Quantum Computer?

Atoms

Atoms are key elements used in certain quantum computers as qubits. In these systems, quantum information is stored in an atom's energy levels or spin states. Quantum computers can carry out calculations by manipulating the atom's state with precise laser or microwave pulses. Since atoms are highly stable and less susceptible to noise, they come in handy for long computations. Technologies like neutral atom quantum computing benefit from this stability to scale up the number of qubits for large-scale problems.

Ions

Ions—which are basically charged atoms—are often used as qubits in quantum computing. In trapped-ion quantum computers, ions are held in place by electromagnetic fields and manipulated with lasers. The ions’ internal energy states store quantum information, while entanglement between ions allows for computations. Ions are highly reliable for quantum error correction and are among the most stable types of qubits. Scaling ion-trap systems to many qubits is a challenge because of how complex it is to manage the traps and lasers.

Photons

Photons, or particles of light, are another component that can serve as qubits in quantum computing—thanks to their speed and resilience to environmental noise. Photonic quantum computers rely on optical devices like beam splitters, mirrors, and detectors to process information. Their natural ability to travel long distances makes them a great choice for quantum communication networks. While photonic systems have potential for scalability, generating and controlling photons comes with its own challenges. 

Superconducting Circuits

Superconducting circuits are a common approach in quantum computing, where qubits are made from loops of superconducting material. These circuits take advantage of quantum states in the electrical current. Controlled using microwave pulses, superconducting qubits are fast and ideal for integrating with existing electronic systems. Companies like IBM and Google use superconducting circuits in their quantum processors. The technology tends to be hardware-intensive because of the ultra-cold temperatures these circuits require.

Quantum Gates

Quantum gates are the building blocks of quantum computers—much like logic gates in classical computers. They manipulate qubits by applying certain operations, such as flipping states or creating entanglement. Unlike classical gates, quantum gates function on superpositions and entangled states, forming the basis of quantum circuits. Examples of quantum gates include the Hadamard gate, which creates superposition, and the CNOT gate, which entangles qubits. 

Quantum Circuits

Quantum circuits are sequences of quantum gates applied to qubits. They are the quantum equivalent of classical computing circuits but work with superpositions and entanglement. A quantum circuit starts by initializing qubits, applies gates to manipulate their states, and ends with measurements to extract results. The design of quantum circuits determines the efficiency and accuracy of quantum algorithms. Shor’s algorithm, for example, uses a carefully designed quantum circuit to outperform classical methods. 

Challenges of Quantum Computing

Error Rates

Because of the fragility of qubits, error rates pose a major challenge to quantum computing. Errors, such as bit-flips and phase-flips, happen because qubits are highly sensitive to environmental noise, electromagnetic interference, and imperfect operations. These can quickly accumulate and make computations unreliable. Error rates are especially problematic during complex calculations, as even small inaccuracies can lead to completely incorrect results. Without effective solutions, the potential of quantum computing remains theoretical rather than practical.

Fortunately, researchers are coming up with quantum error correction techniques to detect and fix errors without collapsing the qubit state. Methods like surface codes and topological codes encode logical qubits across multiple physical qubits to protect information. Meanwhile, fault-tolerant architectures aim to carry out computations while simultaneously correcting errors in real time. Advances in hardware, such as improving qubit stability and manufacturing precision, also help in reducing error rates. 

Scalability

Scaling quantum systems to thousands or millions of qubits is another challenge. Current quantum computers tend to have limited qubits, and adding more actually increases system complexity. Since qubits are interconnected, they require precise control and synchronization. This makes it even more difficult to scale. Larger systems also call for a great deal of hardware resources like cooling and shielding, which are expensive and difficult to maintain.

To solve the scalability issue, researchers are looking into modular approaches, such as linking smaller quantum processors into larger networks. Neutral atom qubits and photon-based systems make it possible to scale due to their potential for higher qubit densities. Companies like Intel are working on silicon spin qubits, using current semiconductor technologies to build scalable quantum systems. Error correction techniques also play a role, as they allow for logical qubits to represent more reliable units of computation. This reduces the need for as many physical qubits. 

Decoherence

Decoherence happens when qubits lose their quantum state because of interactions with their environment. This can be due to temperature fluctuations, vibrations, or electromagnetic interference. Decoherence limits the amount of time qubits can maintain their superposition and entanglement, which are key to quantum computing. Short coherence times mean that quantum computers must perform calculations very quickly before qubits degrade. This makes practical applications somewhat of a challenge.

The solution involves maintaining ultra-cold temperatures with dilution refrigerators to minimize environmental noise—and, in turn, reduce decoherence. It also involves optimizing quantum algorithms for faster computations, minimizing the impact of decoherence. Material innovations, such as using superconducting materials with better coherence properties, are helping improve qubit stability. In the meantime, researchers are developing hybrid quantum-classical systems to split workloads. This way, quantum processors only handle tasks that require coherence. 

Experience the Potential of Quantum Computing Today

BlueQubit is taking steps in quantum computing by democratizing this technology. Its Quantum Software as a Service (QSaaS) platform allows businesses and researchers to benefit from quantum computing without having to invest in expensive quantum hardware. BlueQubit uses advanced quantum processing units (QPUs), emulators, and intuitive tools to facilitate applications like optimization, simulations, and data analysis.

Features like support for multiple QPUs from providers like IBM and Quantinuum, real-time error correction, and tools for developing and testing quantum algorithms bring the spotlight to BlueQubit. Be it improving logistics, enhancing drug discovery, or solving complex financial models, the company gives users the power to benefit from quantum computing in practical, real-world scenarios.

The future of quantum computing is brighter than ever. Recent breakthroughs, like IBM’s advancements in 1,000+ qubit systems and Google’s continued progress in error correction, show that we’re getting closer and closer to achieving fault-tolerant quantum computing. BlueQubit offers a glimpse of what’s to come, preparing businesses for a world where quantum solutions drive innovation. As these technologies keep evolving, the possibilities for solving humanity’s most challenging problems are limitless, giving hope for a smarter future.

Frequently Asked Questions

What are the five main components of quantum computing?

The five main components of quantum computing are qubits, quantum gates, quantum circuits, quantum algorithms, and quantum hardware. Qubits are the basic units of information with the capability of superposition and entanglement. Quantum gates manipulate qubits to allow for computations. Quantum circuits are combinations of gates that form computational processes. Algorithms define problem-solving logic, while hardware is the physical platform, like trapped ions or superconducting circuits.

What are examples of quantum computing?

Examples of quantum computing include Amazon Braket and IBM’s Quantum System One. As a quantum computing service, Amazon Braket provides researchers and developers access to various quantum hardware, such as D-Wave, IonQ, and Rigetti systems, allowing them to solve complex computational problems. Meanwhile, IBM’s Quantum System One simulates molecular interactions to help discover innovative materials for energy storage and superconductors. 

What is the biggest problem with quantum computing?

The biggest challenge in quantum computing is error correction because of qubit instability and susceptibility to environmental noise. Qubits are fragile and prone to errors like decoherence. Building scalable quantum systems that can fix these errors requires advanced error correction methods, significant hardware resources, and precise system controls. This hinders the widespread adoption and practical implementation of quantum computing. 

How do quantum computers actually work?

Quantum computers use qubits to carry out computations with the help of quantum phenomena like superposition and entanglement. Quantum gates manipulate qubits to perform operations, creating circuits that process data. The system encodes information in quantum states, which allows for parallel processing. Unlike classical computers, quantum computers can work in multiple solution spaces at the same time, making them exponentially faster.

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