A Comprehensive Understanding of Quantum Computing's Core Principles
Keywords: quantum computing, qubits, quantum mechanics, computer science, physics, paradigm.
What is quantum computing?
AWS defines Quantum Computing as:
“a multidisciplinary field comprising aspects of computer science, physics, and mathematics that utilizes quantum mechanics to solve complex problems faster than on classical computers” (AWS, n.d.).
The concept of quantum computing is often seen as a subjective view overly fixated on the limitations of classical computing (Dickel, 2016). However, it is fundamentally based on core principles and theoretical truths of quantum mechanics Schneider and Smalley (2024).
Even according to NEXT IAS Team, quantum computing is regarded to as:
“an advanced computing paradigm leveraging quantum mechanics to process information exponentially faster than classical computers” (NEXT IAS Team, 2024).
Gaining an understanding of these theoretical foundations and their background will provide deeper knowledge of quantum computing and enable a more objective perspective on its future in computing.
Core Principles of Quantum Mechanics Understanding these key principles provides a solid foundation for quantum computing (Schneider and Smalley, 2024).
Superposition
IBM defines superposition as “the state in which a quantum particle or system can represent not one possibility, but a combination of multiple possibilities” Schneider and Smalley (2024). This enables quantum parallelism (Microsoft, 2025).
Figure 1: A description of the superposition with the mathematical expression (Microsoft, 2025).
Microsoft explains that classical computing systems, such as current computing devices, allow classical bits to exist in only one of two possible states, 0 or 1. This means classical computers can perform only one computation at a time, following a sequence such as: “if the bit is a 1, do this, if not, do that, then proceed to the next step.” In contrast, a qubit can exist in a superposition of both 0 and 1, allowing quantum computers to process multiple computations simultaneously by considering all possible states of the qubits at once (Microsoft, 2025). This concept can be better understood through its mathematical representation, as shown below.
The mathematical representation of quantum superposition is
|ψ? = α|0? + β|1?
where α and β are complex numbers and |0? and |1? are the states of a quantum bit (qubit) (McGinty, 2023).
Entanglement
This is another principle of quantum mechanics used in quantum computing. IBM defines entanglement as “the process in which multiple quantum particles become correlated more strongly than regular probability allows” (Schneider and Smalley, 2024).
Entanglement plays a crucial role in quantum computing, as it enables the implementation of various protocols and algorithms that are not possible with classical systems (Microsoft, 2025).
Entanglement allows quantum computers to manipulate multiple qubits in a single operation, rather than processing each qubit individually, as in classical computing (Microsoft, 2025). For example, if two qubits are initially prepared in an entangled state, measuring one qubit immediately determines the state of the other. If the first qubit is measured in the state |0?, the second qubit also collapses to |0?. Likewise, if the first qubit is measured in the state |1?, the second qubit collapses to |1? as well (Microsoft, 2025).
Figure 2: An entanglement of two quantum systems (Microsoft, 2025).
Entanglement is also a fundamental resource for quantum error correction, which is essential for protecting quantum information from decoherence and other errors. By generating and manipulating entangled states, quantum computers can detect and correct errors in ways that classical computers cannot Microsoft (2025).
Decoherence
Decoherence is defined by IBM as: ?“the process in which quantum particles and systems can decay, collapse or change, converting into single states measurable by classical physics” (Schneider and Smalley, 2024).
Decoherence is considered the greatest obstacle to quantum computing. It occurs when a quantum system loses its coherence or quantum behavior due to interactions with its environment. It is the process by which the quantum properties of a system “leak” into the surrounding environment, causing the system to behave more classically and lose its quantum superposition and entanglement properties (Quandela, 2025).
Figure 3: Sketches of (a) quantum dissipation of a two-level system induced by its environment, (b) dissipation suppressed by white noise (Jing and Wu, 2013).
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Interference
“Interference is the phenomenon in which entangled quantum states can interact and produce more and less likely probabilities defined” Schneider and Smalley (2024).?
This occurs due to the wave-like nature of quantum particles such as electrons or photons. When a particle exists in a superposition of multiple states, these states can interfere with each other, resulting in either constructive or destructive interference (Microsoft, 2025).
Interference is fundamental to many quantum algorithms and contributes to significant computational speedups. One example is Grover’s algorithm, which is used for unstructured search. Another example is the Quantum Fourier Transform (QFT), a crucial algorithm in quantum computing that enables efficient computation of certain mathematical functions. The QFT leverages superpositions of different states and quantum interference to compute the Fourier transform of a quantum state. The interference between different paths in the QFT enhances the probability of measuring the correct solution while suppressing incorrect outcomes, resulting in faster computation (Microsoft, 2025).
Quantum interference is also essential in quantum phase estimation, a technique used in various quantum algorithms to estimate the phase of a quantum state. This process relies on interference between different quantum states, controlled through the application of quantum gates and measurement of the resulting probability distribution. Additionally, interference plays a critical role in quantum error correction, which protects quantum information from decoherence and other errors. By analyzing the interference patterns of qubits, quantum computers can detect and correct computational errors (Microsoft, 2025).
Figure 4: Quantum interference depicted in a quantum system (Microsoft, 2025).
References
AWS, n.d. ‘What is Quantum Computing?’, AWS. Available at: https://aws.amazon.com/what-is/quantum-computing/#:~:text=Quantum%20computing%20is%20a%20multidisciplinary,hardware%20research%20and%20application%20development [Accessed 5 February 2025].
Dickel, C., 2016. ‘Media Misconceptions: Quantum versus Classical Computers’, QuTech. Available at: https://blog.qutech.nl/2016/08/04/media-misconceptions-quantum-versus-classical-computers/ [Accessed 5 February 2025].
Jing, J. and Wu, L.A., 2013. ‘Control of decoherence with no control’, Scientific Reports, 3, p.2746. Available at: https://doi.org/10.1038/srep02746 [Accessed 5 February 2025].
McGinty, C., 2023. ‘The mathematical representation of quantum computing is based on quantum gates, which are unitary matrices used to manipulate the state of qubits’, LinkedIn. Available at: https://www.dhirubhai.net/pulse/mathematical-representation-quantum-computing-based-gates-mcginty#:~:text=Quantum%20Superposition%3A,a%20quantum%20bit%20(qubit) [Accessed 5 February 2025].
Microsoft, 2025. ‘Azure Quantum | Entanglement’, Microsoft. Available at: https://quantum.microsoft.com/en-us/insights/education/concepts/entanglement#:~:text=Entanglement%20enables%20quantum%20computers%20to,states%20between%20two%20distant%20systems [Accessed 5 February 2025].
Microsoft, 2025. ‘Azure Quantum | Interference’, Microsoft. Available at: https://quantum.microsoft.com/en-us/insights/education/concepts/interference [Accessed 5 February 2025].
Microsoft, 2025. ‘Azure Quantum | Superposition’, Microsoft. Available at: https://quantum.microsoft.com/en-us/insights/education/concepts/superposition#:~:text=Superposition%20is%20a%20fundamental%20attribute,the%20possibility%20of%20quantum%20parallelism [Accessed 5 February 2025].
NEXT IAS Team, 2024. ‘Quantum Computing’. [online] Available at: https://www.nextias.com/blog/quantum-computing/ [Accessed 5 February 2025].
Quandela, 2025. ‘What is Quantum Decoherence?’, Quandela. Available at: https://www.quandela.com/resources/quantum-computing-glossary/quantum-decoherence/ [Accessed 5 February 2025].
Schneider, J. and Smalley, I., 2024. ‘What is quantum computing?’, IBM. Available at: https://www.ibm.com/think/topics/quantum-computing [Accessed 5 February 2025].