Technology & Medicine › Internet, genomes & AI
Quantum computers
2019 ('quantum supremacy' claim, disputed)· Invention or discovery· Communication & computing
DebatedHistorians or scientists disagree about what happened, when, or why.
Computers that use the rules of quantum physics, aiming to tackle certain problems far beyond ordinary computers; still early and error-prone.
See it on the Technology & Medicine map →How it works
Ordinary computer bits are 0 or 1. Quantum bits, or qubits, can hold a blend of both (superposition) and be linked to each other (entanglement), which in principle lets them solve certain specialized problems far faster. Richard Feynman proposed the idea in 1981; in 1994 Peter Shor showed such a machine could break common encryption. In October 2019 Google claimed its 53-qubit Sycamore chip did in 200 seconds a task that would take a supercomputer 10,000 years.
Why it mattered
If scaled up, they could simulate molecules for drugs and materials and break much of today's internet encryption, which is already driving a switch to 'quantum-safe' codes.
How we know
Google's 2019 paper in Nature and IBM's rebuttal; peer-reviewed experiments by Google, IBM, Quantinuum and others; the US standards agency NIST's 2024 quantum-safe encryption standards.
Still unknown or debated
IBM argued the 2019 task would take a supercomputer days, not millennia; whether and when error-corrected machines will do commercially useful work remains uncertain.
Connections (3)
▸Electronic computer (Z3, Colossus, ENIAC) may be outpaced on some problems by Quantum computersMostly agreed
The connection
Electronic computers, from ENIAC on, process bits that are definitely 0 or 1, and nearly all tasks will stay with them. Quantum computers use qubits governed by quantum physics, which in theory lets them tackle a few problem types, such as factoring huge numbers or simulating molecules, vastly faster. Ordinary computers still control and check every quantum machine.
When and how
ENIAC in Philadelphia, 1945–46; Richard Feynman's 1981 talk at an MIT conference proposing quantum simulation; quantum labs at Google, IBM and others from the 2010s.
How sure are we?
Mathematical results such as Shor's 1994 algorithm show the potential speedup; real hardware has shown an advantage only on narrow, artificial tasks so far.
Debates and open questions
Whether quantum computers will beat classical ones on any commercially useful problem, and when, is debated; clever classical methods keep matching quantum claims.
▸Laser controls the trapped-ion qubits of some Quantum computersMostly agreed
The connection
Some quantum computers, built by companies such as Quantinuum and IonQ, store qubits in individual charged atoms (ions) held in electric fields. Precisely tuned laser beams cool the ions almost to a standstill, set and change their quantum states to compute, and read out results by making them glow. Lasers also drive neutral-atom and light-based machines.
When and how
Trapped-ion computing proposed by Ignacio Cirac and Peter Zoller in 1995; the first such logic gate was built that year at NIST in Boulder, Colorado, by David Wineland's group.
How sure are we?
Peer-reviewed experiments since 1995 and company papers document laser control; Wineland shared the 2012 Nobel Prize in Physics for this line of work.
Debates and open questions
Whether laser-controlled ions or the superconducting chips of Google and IBM, which use microwaves instead, will scale better is an open race.
▸Quantum computers may one day break the encryption of The Internet (TCP/IP)Mostly agreed
The connection
Internet security relies on codes such as RSA, which are safe because ordinary computers would take impossibly long to break huge numbers into their factors. In 1994 Peter Shor showed a large quantum computer could do it quickly. Today's machines are far too small and error-prone, but governments are already switching to new 'post-quantum' codes.
When and how
Shor at Bell Labs in New Jersey, 1994; the US standards agency NIST published its first post-quantum encryption standards in August 2024.
How sure are we?
Shor's method is mathematically proven, so the threat is real in principle; no quantum computer has yet factored a number anywhere near the size used in encryption.
Debates and open questions
When, or whether, a large enough quantum computer will be built is fiercely debated, with estimates ranging from about a decade to never; stolen data could be decrypted later.