An ancilla qubit is entangled with a subset of data qubits, in which the former is measured to infer the state of the latter without causing any disruption to the quantum system. To preserve the quantum state of qubits during QEC, the research team at Quantinuum use ancilla qubits, whose job is to signal errors in the actual qubits (or data qubits) performing the calculations. Quantinuum’s achievement is groundbreaking as they have shown that it is now possible to perform QEC to detect and correct errors in real-time on a quantum computer. Entangled qubits stand, divided qubits fall. However, only one round of error correction is allowed for each logical qubit in a calculation and this has generally been retrospective – “noise” is only corrected in a post-processing step. This qubit would then be less prone to errors, with the added benefit of not disrupting quantum information while probing for errors. To go about fixing this, researchers have proposed to quantum-mechanically entangle several physical qubits to make a single logical qubit. Attempts to directly detect and correct these errors on a physical qubit also corrupts its “quantumness” – principles used to correct bit flips don’t apply here. ![]() The former is akin to those in classical computers and correcting them are relatively straightforward: each bit is copied several times, in which a random error (such as a 0 flipping to a 1) can then be recognised and corrected using a simple majority rule.īut as quantum computing harnesses the principle of superposition, an error that causes phases to flip will also interfere with calculations. ![]() Two main types of errors occur in a quantum computer: bit flips and phase flips. These two features are key to realising a fully error-tolerant quantum machine that can be scaled up and is practical beyond specialised applications.īut first, how do errors in quantum computers differ from those in classical computers? Isolating the noise.ĭetecting and then correcting a quantum error is not for the faint-hearted. On top of that, error correction can also be done multiple times on a single qubit during the calculation. Now, researchers at Quantinuum have demonstrated a technique that allows errors to be detected in real-time as the quantum computation proceeds. Since then, the field of QEC has blossomed and become crucial in building a practical quantum computer. To tackle this quantum conundrum, in the 1990s mathematician Peter Shor wrote a quantum error correction (QEC) code to find out if a quantum error has occurred without actually measuring the state of the qubit itself. Using error-correcting schemes like those in classical computers is unfeasible as making direct measurements would destroy the delicate quantum states and disrupt calculations. ![]() While a quantum computer has the potential to solve some problems much faster than a classical computer, its quantum states are too delicate – a fickle environment would unavoidably wreak havoc on the quantum information in the machine, causing the computer to lose its practicality. ![]() Quantum bits, or qubits, are fussy and fragile.
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