Your laptop can stream movies in 4K, juggle a dozen browser tabs, and maybe even beat you at chess. But ask it to accurately simulate the quantum behaviour of even a modest molecule like caffeine and the calculation quickly becomes computationally prohibitive. The problem isn’t that your machine is outdated – it’s that it’s classical.
Classical computers [1], the kind we’ve trusted for decades, process information in bits [2]: 0s and 1s, on or off. That works beautifully for spreadsheets, video calls and most of daily life. But nature doesn’t think in binary. At the scale of atoms and particles, the universe follows a very different script: the probabilistic, often counterintuitive rules of quantum theory. That’s where quantum computing comes in.
What is quantum computing? At its core, quantum computation is a new way of processing information that harnesses the principles of quantum mechanics to tackle problems that stump even the fastest classical supercomputers. Instead of ordinary bits, it uses qubits [3] – units of information governed not by simple on/off logic, but by the same quantum laws that shape the tiniest building blocks of reality.
It sounds arcane, almost otherworldly. But it can be broken down into plain language. Here, we’ll explain quantum computing in simple terms: what it is, how it works and why it matters.
What is quantum computing?
To understand what makes quantum computation so powerful, you need to start with the bit – the basic unit of information in classical machines. A bit can be either 0 or 1. But in a quantum computer [4], we use qubits, which can exist in superpositions [5] of 0 and 1. In other words, a qubit carries a probability amplitude for being measured as either state. This phenomenon allows quantum machines to process many possibilities simultaneously. That’s qubits made simple, but things get even stranger.
Qubits can also be linked through entanglement [6]. This is a uniquely quantum connection where measuring one entangled qubit immediately determines the correlated outcome of the other, regardless of the distance between them. Yet no information actually travels between the qubits. When combined, superposition and entanglement give quantum computers a way of exploring problems that defy the limits of classical logic.
So what’s the catch? Qubits are fragile, prone to error and hard to control. But as the technology matures, the promise isn’t just faster performance, but a fundamentally different way of computing.
This is a simple explanation of quantum computing. Beneath the surface, though, the mechanics are even more fascinating, and that’s where we’ll turn next.
The strange logic of qubits
To grasp how a quantum computer works, we need a touch of entry-level quantum physics, the science of how particles behave at the smallest scales. A quantum processor [7] doesn’t perform computation using classical transistors. Instead, it manipulates physical quantum systems as qubits, harnessing the key principles of quantum computing: superposition, entanglement and interference [8]. This isn’t just faster computing, it’s an entirely new kind of logic.
Ask a physicist to “explain quantum computing like I’m 5” and they might use this simple analogy. Imagine flipping a coin. When it lands, it’s either heads or tails – that’s a classical bit. But while the coin is spinning, it hovers in a state of possibility, both heads and tails at once. That’s superposition, and it’s what gives qubits their uncanny power.
Now imagine not one coin, but dozens, all spinning at once. In a classical world, each coin would flip independently. In a quantum world, though, these coins can become entangled. It’s as if they were mysteriously linked: when one coin finally lands on “heads”, the others instantly settle into matching outcomes, no matter how far apart they are. Nothing travels between them; it’s the connection itself that is non-classical.
To harness this strange behaviour, quantum machines apply operations known as quantum gates [9], steering qubits step by step through a calculation. At the end, a classical computer measures the final state to extract and interpret the result. In essence, then, a quantum computer doesn’t plod through problems one step at a time. It fans out across a landscape of possibilities, and that changes not only how quickly we compute, but what is computable at all.
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Machines at the edge of physics
Quantum computation isn’t just about speed. It tackles problems that rapidly outgrow the capabilities of classical computers. But to make that leap, the strange rules of quantum mechanics have to be made real in hardware. Just as microchips store and process classical bits, a quantum processor is the platform where qubits live, interact and perform their peculiar dance.
The challenge is fragility. A quantum state can be undone by almost anything. A trace of heat, a stray vibration, even background radiation can trigger decoherence [10], forcing qubits into fixed states before the calculation completes. This destroys superposition and entanglement, ruining the computation process. To preserve coherence [11] long enough for a calculation to play out, quantum machines run at temperatures colder than outer space, inside ultra-controlled chambers. Dilution refrigerators, supercooled materials and precision electronics hold coherence just long enough for the computation to unfold.
Layered on top of this fragile machinery is the software that makes it usable. Platforms like Qiskit, Cirq and PennyLane let researchers write programs on an ordinary computer, which are then translated into the strange logic of a quantum device through quantum gates. In practice, these tools act as a bridge between two worlds – the everyday classical and the profoundly quantum – making it possible to test ideas and bring real-world applications closer to reality.
Why quantum changes the game
Quantum isn’t just another step in computing, it’s a break from everything that came before. By tapping into the strange behaviour of qubits, machines can exploit quantum effects to tackle certain problem spaces that scale prohibitively for classical systems.
The early signals are already here. Researchers have used quantum processors to perform early simulations of molecular systems, chart supply chains that self-optimize and push machine learning into new territory. These aren’t faster versions of what we already do; they’re problems that become prohibitively expensive for classical machines as they scale.
The advantages of quantum computation are striking:
- Speed-ups that grow dramatically with scale
- Simulations precise enough to unlock new chemistry and materials
- Breakthroughs in optimization that can ripple through whole industries
- Smarter, more efficient machine learning models
- Solutions to problems once written off as impossible
As hardware stabilizes and algorithms [12] mature, what’s now confined to the lab could slowly move into production. Industries from medicine to finance, energy to transport, stand to be reshaped, and the boundaries of the computable will break into entirely new terrain.
From cracking codes to curing diseases
The first glimpse of quantum’s real-world applications came in 1994, when mathematician Peter Shor unveiled an algorithm that changed the field overnight. Shor’s algorithm [13] showed that a quantum machine could, in principle, factor large numbers exponentially faster than classical methods, given a sufficiently large and error-corrected quantum computer. This breakthrough hinted at seismic implications for cryptography [14].
Suddenly the stakes were clear. A scalable quantum computer, once realized, could break encryption systems like RSA, the backbone of everything from online banking to national security. But quantum doesn’t just threaten security, it also offers ways to protect it. Quantum key distribution (QKD) [15], for instance, uses the laws of quantum mechanics to create communication channels so secure they identify any attempt at eavesdropping.
But cryptography is only the beginning. By harnessing qubits and their strange properties, quantum computation promises to transform industries well beyond security.
Early quantum applications point to:
- Drug discovery: simulating molecules with high accuracy, potentially accelerating the development of new medicines as the hardware and algorithms improve
- Materials science: designing superconductors and next-generation alloys that redefine efficiency and strength
- Finance: modelling markets, managing risk and pricing complex assets with unprecedented precision
- Logistics: optimizing shipping routes and warehouse flows across global supply chains
- Climate: simulating Earth’s atmosphere at scales classical models can’t reach, sharpening forecasts and shaping policy
These are the earliest signs of a potentially much bigger shift. Each advance takes us deeper into uncharted territory, where the rules of computation are rewritten and the boundaries of possibility keep moving.
The race for quantum supremacy
Quantum computing is moving quickly. In 2024, Google unveiled Willow, a prototype quantum processor that solved in minutes a calculation so complex it would have taken the classical supercomputers an estimated 10 000 years to simulate. Built as a research platform, Willow demonstrated just how radically different quantum logic can be. Prior to that, IBM’s Eagle processor had already crossed the 100-qubit threshold, while Google’s Sycamore claimed “quantum supremacy” [16] by completing a task far beyond the reach of classical machines.
In 2025, Microsoft raised the stakes with the announcement of its Majorana 1 quantum chip, built on a newly observed state of matter. These topological qubits [17] – quantum states built from Majorana quasiparticles – promise greater stability and fault tolerance, potentially cracking the toughest challenges in the field: error correction [18] and resistance to decoherence. If proven scalable, they could accelerate breakthroughs in pharmaceuticals, clean energy, and even artificial intelligence.
Governments are investing too. China has committed over USD 15 billion (MERICS, Dec. 2024) in public funds to quantum R&D, while global tech giants race to turn the principles of quantum mechanics into technologies with real-world applications. The science is still evolving, but the trajectory is clear: practical quantum computing is gradually moving from the lab into reality.
Standards for “unclassical” computers
As quantum technology accelerates, something less visible – but just as essential – is taking shape: the foundation of shared rules, language and structure. In 2024, ISO and the International Electrotechnical Commission (IEC) launched a dedicated technical committee, ISO/IEC JTC 3, to do exactly that. Its first deliverable, ISO/IEC 4879, defines the official vocabulary of quantum computing. Quietly but decisively, it sets the terms for how the field will be described, discussed and developed worldwide.
Why does that matter? Because without shared standards, quantum’s rapid growth risks splintering into silos: incompatible platforms, conflicting definitions and a maze of technical confusion. That kind of fragmentation slows progress just when the sector needs coherence most. Standards bring alignment. They enable interoperability, support regulation and give researchers and developers a common starting point – a shared logic for the most unclassical of computers.
- ISO/IEC 4879:2024Information technology — Quantum computing — Vocabulary
Billions at stake, futures on the line
In today’s tech-driven world, quantum is no longer a thought experiment – it’s a strategic frontier. The world’s biggest players are racing to build machines powerful enough to do what no computer has done before, while designing the software that will make them useful outside the lab.
The prize? Solutions to problems once deemed unreachable: new medicines tailored to the complex molecule, global supply chains optimized in real time, climate systems modelled with unprecedented precision, financial risks mapped before they materialize. Entire industries stand on the brink of reinvention.
The money is already flowing – billions in public and private investment, and growth curves that only point upward. Governments see it as a matter of security and competitiveness. Companies see it as the next great platform shift. The science is advancing, the momentum undeniable, and the race is on. The real question now isn’t whether quantum computing will change our world, but who will be first across the finish line.
- Classical computer: computer that processes information using classical bits
- Bit, binary digit: either of the digits 0 or 1 when used in the binary system
[ISO/IEC 2382:2015, 2121573] - Qubit: quantum system with two basis states
Note: Qubit stands for quantum bit; it is the smallest unit of quantum information.
[Adapted from ISO/IEC 4879:2024, 3.3.3] - Quantum computer: fully programmable quantum processor that can implement or approximate any unitary dynamics defined within its full Hilbert space
Notes:
- In circuit-based quantum computing, a quantum computer has access to a universal set of quantum gates.
- Quantum computers most commonly use quantum information encoded in qubits.
[Adapted from ISO/IEC 4879:2024, 3.4.10] - Superposition: complex linear combination of two or more different quantum states
[ISO/IEC 4879:2024, 3.2.8] - Entanglement: property of a quantum state within a joint quantum system, consisting of at least two subsystems, for which the quantum state cannot be described in terms of independent characteristics of its individual constituents
[ISO/IEC 4879:2024, 3.2.10] - Quantum processor: tangible device that performs quantum information processing
[ISO/IEC 4879:2024, 3.4.8] - Interference: coherent superposition of wave functions (quantum states) of a physical system
[ISO/TS 80004-12:2016, 2.7] - Quantum gate: applied quantum operation that transforms input quantum states into output quantum states
[Adapted from ISO/IEC 4879:2024, 3.4.2] - Decoherence: loss or degradation of quantum coherence
[Adapted from ISO/IEC 4879:2024, 3.2.19] - Coherence (quantum): existence or extent of unambiguous phase relationships between possible states of a quantum system
[Adapted from ISO/IEC 4879:2024, 3.2.18] - Algorithm (quantum): algorithm for use on a quantum processor
Note: Quantum algorithms can be designed so that they need to be run multiple times to extract the required result; for example, to overcome noise or as a means to implement a target algorithm efficiently using approximate quantum circuits.
[Adapted from ISO/IEC 4879:2024, 3.4.9] - Shor’s algorithm: a quantum Fourier transform-based algorithm for factoring a (large) integer
[ISO/IEC 9594-12:2025, 3.2.23] - Cryptography (quantum): cryptography that utilizes quantum communication in an essential way
[ISO/IEC 4879:2024, 3.6.2] - Quantum key distribution (QKD): use of quantum phenomena for cryptographic purposes
[ISO/TS 80004-12:2016, 6.6] - Quantum supremacy: point at which a quantum computer performs a computation that is unfeasible for classical computers within practical resource limits
- Topological qubits: qubits in which quantum information is encoded in topological properties of a system, providing inherent resistance to certain types of errors
Note: Topological qubits are often linked to Majorana zero modes for fault-tolerant quantum computing. - Error correction (quantum): procedure to diagnose and correct errors in the constituent parts of a logical qubit without measuring any logically encoded quantum information, by exploiting the logical qubit’s symmetries
[Adapted from ISO/IEC 4879:2024, 3.4.6]