Scientists edge closer to fault-free quantum computers

14 Jul 2023

Image: © RareStock/

A preprint study by Quantiniuum claims a new error-detecting code was able to accurately simulate a hydrogen molecule and could help create more advanced quantum computers.

A team of scientists claim to have achieved a breakthrough towards fault-free quantum computers, by successfully simulating a chemical molecule on a quantum processor.

Quantum computing company Quantinuum said it was able to simulate a hydrogen molecule by using a “fault tolerant algorithm” on the company’s H1 quantum computer.

Quantinuum claims this is an “essential step” to speed up the discovery of molecules and reduce the time to generate commercial and economic value in the future.

It is believed that when true quantum computers become reality, they will be able to handle extremely complicated simulations that conventional computers can’t solve, which could lead to new pharmaceutical discoveries or the creation of new materials.

However, these quantum machines are so sensitive that their calculations suffer from errors. Imperfect control signals, interference from the environment and unwanted interactions between quantum bits – qubits – can lead to “noise” that disrupts calculations.

The risk of errors grows as more qubits are added to a quantum computer, which complicates attempts to create more powerful machines or solve more complicated problems.

Error-detection code

In a preprint study, the team claims to have overcome the challenge by using an error-detection code which saves quantum resources by immediately discarding calculations if the code detects qubits that have produced errors.

The team used this code to make three “logical qubits” which are composed of multiple physical qubits. In February, Google researchers claimed that encoding information across various physical qubits into logical qubits was able to reduce the number of errors.

The quantum computer company claims its code – combined with its own hardware and software – led to more accurate simulation results than those achieved without the error-detecting code.

Quantinuum senior researcher Dr Kentaro Yamamoto said simulating a hydrogen molecule was an “excellent experimental result” and shows “how fast we continue to progress”.

“This result may reflect the start of a new chapter for quantum computing professionals, where we can begin to adopt early fault-tolerant algorithms on near-term devices, using all the techniques that will ultimately be required for future large-scale quantum computing,” Yamamoto said.

Earlier this year, scientists in Sweden claimed they were able to minimise errors in a quantum computer by comparing the results to a conventional supercomputer, a technique that could eventually be scaled up to solve more complicated problems.

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Leigh Mc Gowran is a journalist with Silicon Republic