Quantum Computing
Why a Quantum Computer Isn't Just a Faster Classical Computer
The most powerful quantum computer in the world would lose to your laptop at most tasks — and that's exactly what makes it revolutionary.
The Idea
Classical computers, no matter how fast, do one thing at a time in sequence. They work in bits — each one is either a 0 or a 1. Quantum computers work in qubits, and here's where the genuine strangeness begins: a qubit can exist in a superposition of 0 and 1 simultaneously — not metaphorically, but physically. It's only when you measure it that it collapses to a definite state. This isn't a clever trick for storing more data. It's a fundamentally different way of computing. Where it gets powerful is in how qubits interact. Through a phenomenon called entanglement, two qubits can be linked so that the state of one instantly informs the state of the other, regardless of distance. String together enough entangled qubits and you can, in theory, explore a vast number of possible solutions to a problem simultaneously — not by trying each one in sequence, but by encoding them all into the quantum state at once and then designing the computation to amplify the right answer. The counterintuitive part: quantum computers aren't universally faster. They offer an advantage only for specific types of problems — those involving enormous search spaces, pattern-finding in complex systems, or simulating the quantum behaviour of molecules. For anything else, a classical processor wins easily. The art of quantum computing is recognising which problems have that structure — and then figuring out how not to let the fragile quantum state collapse before you get your answer.
In the World
In 2019, Google announced that its 53-qubit processor, Sycamore, had completed a specific mathematical calculation in 200 seconds — a calculation they claimed would take the world's most powerful classical supercomputer around 10,000 years. IBM contested the figure, arguing their own supercomputer could do it in 2.5 days with clever optimisation. But even granting IBM's counter, the gap remained staggering. The task itself was deliberately esoteric: sampling the output of a random quantum circuit. It has no obvious real-world application. Google chose it precisely because it plays to quantum's structural strengths — it's the kind of problem that's almost impossible to verify classically, which is both what makes it a compelling demonstration and what made it controversial. Critics pointed out that proving 'quantum advantage' on a problem nobody actually needs solved is a long way from proving quantum computing is practically useful. That tension is still live. In 2023, IBM unveiled a 1,000-qubit processor. But raw qubit count is misleading — noise and error rates matter enormously. Qubits are extraordinarily fragile; even stray vibrations or electromagnetic interference can cause decoherence, collapsing the quantum state before the computation finishes. The field's core engineering challenge isn't building more qubits, it's building qubits that stay quantum long enough to be useful. Most researchers think genuinely fault-tolerant quantum computing — the kind that would break modern encryption or simulate protein folding — is still a decade away, at minimum.
Why It Matters
The reason this isn't just an esoteric physics curiosity is that quantum computing threatens one of the pillars of digital security. Most encryption today — protecting banking, messaging, government communications — relies on the fact that factoring enormous numbers into their prime components is computationally intractable for classical computers. A sufficiently powerful quantum computer running an algorithm called Shor's algorithm could crack that in hours. Governments and cybersecurity agencies are already taking this seriously. The US National Institute of Standards and Technology finalised its first set of post-quantum cryptography standards in 2024 — new encryption methods designed to be resistant even to quantum attack. The transition will take years and affect nearly every connected system on earth. Beyond security, the more optimistic applications — simulating molecular interactions to design new drugs, optimising vast logistical networks, accelerating machine learning — are genuinely transformative if the hardware catches up. The honest position is that quantum computing is neither the overhyped revolution some press releases suggest, nor a distant fantasy. It's a specific tool, still being built, for a specific class of problems — and some of those problems happen to be enormously consequential.
A Question to Ponder
If quantum computing eventually breaks the encryption protecting most of our digital infrastructure, who decides how that capability gets used — and do we have any reason to trust that decision will be made well?
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