Quantum computers promise to solve problems that would take today’s most powerful supercomputers thousands of years. Here’s how they work, what they could do, and why they’re not on your desk yet.
Ordinary computers, from phones to supercomputers, store and process information as bits. Each bit is either a 0 or a 1.
Quantum computers use quantum bits, or qubits. Thanks to the rules of quantum physics, which govern how tiny particles behave, a qubit can exist in a combination of 0 and 1 at the same time, a property called superposition.
Qubits can also be linked through a property called entanglement, so the state of one is connected to another. Together, these properties let quantum computers explore huge numbers of possibilities at once for certain kinds of problems.
That doesn’t make them faster at everything. For everyday tasks like browsing the web or writing documents, ordinary computers are better. Quantum computers are expected to excel at specific problems that are practically impossible for classical machines.
What they could do
The most promising uses include simulating molecules to design new medicines and materials, such as better batteries and fertilisers, along with optimisation problems in logistics and finance.
Why they’re hard to build
Qubits are extremely fragile. Tiny amounts of heat, vibration or electromagnetic noise can disrupt them and cause errors. Many quantum computers must be cooled to temperatures colder than outer space.
Today’s machines have a limited number of qubits and make frequent errors. The industry’s big goal is a “fault-tolerant” quantum computer, with enough reliable qubits to correct its own errors and run useful calculations. Google, IBM, Microsoft and specialist start-ups are all racing towards it, and have reported important progress on error correction in recent years.
The threat to encryption
Much of the encryption that protects online banking, messages and government secrets relies on maths problems that ordinary computers can’t solve in a reasonable time. A large, reliable quantum computer could solve some of them.
Security agencies warn that hackers may already be stealing encrypted data to decrypt later. In 2024, the U.S. standards body NIST released the first post-quantum encryption standards, designed to resist quantum attacks, and governments, including Australia’s, are urging organisations to start upgrading.
Australia’s role
Australia has a strong history in quantum research. In 2024, the federal and Queensland governments committed about $940 million to U.S.-based company PsiQuantum to build what it hopes will be one of the world’s first useful, large-scale quantum computers in Brisbane.
Supporters say it could make Australia a leader in a valuable new industry. Critics have questioned the size of the public investment in a technology that hasn’t yet been proven at scale.
