NederlandsQubit
A qubit is the unit of computation of a quantum computer. Unlike an ordinary bit it can be in several states at once, but it is also very sensitive to disturbance.
A qubit is the smallest unit of computation of a quantum computer. An ordinary bit is a 0 or a 1. A qubit can be in both states at once, in a particular mix, until you measure it. That lets quantum computers do some calculations much faster than ordinary computer chips, for example simulating molecules for new medicines and materials.
How does it work?
A qubit is a very small particle or component that has quantum properties. There are several kinds. Some are tiny superconducting current loops on a chip. Others are charged atoms (ions) that hover above a chip in electric fields and are operated with lasers, or electrons in silicon.
The drawback is that qubits are very fragile. A little heat, a vibration or an imprecise laser pulse is enough to disturb them, and looking at a qubit disturbs it too. That is why many qubits are made to work together as one reliable qubit, a logical qubit, which can catch its own errors.
Why it matters
The number of qubits and their quality determine what a quantum computer can do. Japanese researchers controlled five qubits on a silicon chip at the same time, through one shared control line, and kept the accuracy at around 99.9 per cent (link). Silicon is the same material used in ordinary chips. Quantinuum used its 98-qubit computer Helios to show how well errors can be caught: per check round, on average only five times in a million did something go wrong (link). That brings a quantum computer that can do truly useful computation closer.
Articles about Qubit
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PSI: AI found proof of a 2008 conjecture on the limits of quantum computers
The US company Physical Superintelligence says its AI system found a proof of the Aaronson-Ambainis conjecture, an open question from 2008 about when quantum computers are much faster. The program Lean has approved the proof; fellow researchers are now checking it.
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One short measurement beforehand halves a qubit's errors
A team led by the University of Regensburg had a qubit briefly measure which frequency it was on before each series of calculations, then adjusted the controls automatically. Errors fell by about 54 per cent. The next step is more qubits at once.
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New calculation: quantum computer needs far fewer qubits to break internet encryption
French quantum company Alice & Bob calculates that a quantum computer with about 23,000 qubits could break the widely used RSA encryption in just over three days. Such a machine does not exist yet, but the calculation shows why switching to quantum-safe encryption now is wise.
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Tencent lets AI build its own tools for protein research and mathematics
Tencent has presented the second version of its research AI, Hyra. It delivers not only solutions but also tools that can be used again later. Models for proteins and molecules are already public, so other researchers can now test them themselves.
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Google demonstrates magic state cultivation on Willow: 40 times fewer errors
Google Quantum AI tested a new way to make magic states on its Willow chip: special states that a quantum computer needs for its hardest operations. The errors in them became about 40 times smaller. The result is published in Science.
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German company makes a molecule that stores quantum information and can pass it on with light
The German company NVision and researchers from Ulm and Jerusalem describe in Nature a molecule of carbon and hydrogen that stores quantum information and can pass it on with light. Such a building block could later link quantum computers together.
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IBM links two quantum chips with 80-centimetre cables
IBM researchers connected two quantum chips of 120 qubits each with four superconducting links of 80 centimetres. The quantum information came across with an average fidelity of 99 per cent. It is a step towards quantum computers built from separate modules.
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Japanese researchers control five quantum bits in silicon at once, with almost no errors
Researchers at RIKEN in Japan controlled five quantum bits on a silicon chip at the same time, through one shared control line. They found the biggest source of errors and kept accuracy at around 99.9 per cent. That helps to build larger quantum computers.
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Quantum computer keeps chaos under control on 100 qubits: a step towards fault-tolerant computing
Researchers from Rutgers, IBM and other institutions had a quantum computer check and correct itself thousands of times while it was computing. It is not yet a working fault-tolerant quantum computer, but it is an important building block for one.
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Quantum computer catches its own errors so well that only 5 in a million remain
Quantinuum's Helios quantum computer set a new record in error correction: on average, something went wrong five times in a million checking rounds. That is ten times better than the previous record. The next step is to show this for more complex calculations too.
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Nvidia simulates a 104-qubit quantum circuit on a European supercomputer, real errors included
Nvidia and the German research centre Jülich used the JUPITER supercomputer to simulate how a 104-qubit quantum computer makes an important building block, including the errors that real hardware makes. This lets designs be tested before they are built.
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Stanford builds a grid of more than 600 light traps to link quantum computers made of atoms
Physicists at Stanford built a grid of more than 600 tiny light traps, each of which can catch the light of a single atom. That helps to read out quantum computers made of atoms faster and later to link them together.
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Oxford keeps a quantum link between atoms in two places alive for more than ten seconds
Physicists at the University of Oxford linked atoms of strontium and calcium in two places into a single quantum state. By passing the link on to calcium, it lasted more than ten seconds instead of milliseconds. A step towards networks of quantum computers.
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Electron pairs survive after superconductivity is gone
Physicists saw that electrons in a metal keep forming pairs even when it is just too warm for superconductivity. That helps to understand how electricity without losses comes about. The next step is to see whether it also happens inside the material.
