Microsoft calculates with 12 error-corrected qubits
Researchers from Microsoft and Quantinuum combine 56 qubits into 12 computing units and use them to simulate a chemical reaction.
Cooling chamber of the Quantinuum quantum computer
(Image: Josh Wood)
A research team from Microsoft and Quantinuum combined quantum error correction with the successful execution of arithmetic operations for the first time. Together with an AI model and classical computing systems, this quantum computer solved a problem from quantum chemistry. Microsoft presents the results in a blog post.
The US company Quantinuum, led by Rajeeb Hazra, was created through the merger of Cambridge Quantum and Honeywell Quantum Solutions. The company uses trapped ions, i.e. charged atoms, as qubits. Quantinuum presented its H2 quantum computer with 56 qubits in June of this year. Users can access the commercial machine via Quantinuum or Microsoft Azure.
Effectively correcting qubit errors
Due to the unstable nature of qubits, quantum computers are still very error-prone. If several calculation steps are performed in succession, the results – are noisy and therefore unusable. Recognizing qubit errors and correcting them during the calculation is the goal of quantum error correction.
(Image: Quantinuum)
Instead of storing quantum information in a single qubit, it is distributed across several so-called physical qubits. Together, these form a logical qubit, i.e. a computing unit. This means that the information is retained even if a single physical qubit makes an error. To correct errors on Quantinuum's H2 machine, the team used an algorithm from Microsoft.
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The team combined 56 physical qubits into 12 logical qubits. They entangled them, i.e. brought them into a complex, quantum-physical superposition state. The error rate of operations on qubit pairs amounted to 0.11 percent. This value is 22 times smaller than the error rate for individual physical qubits. The team also carried out various fault-tolerant calculations with the logical qubits. This was the first demonstration of the successful combination of quantum calculations and error correction.
With these advances, the team is building on results from the spring. At that time, they had already combined 30 physical qubits into four logical qubits. The error of the logical qubits was 800 times smaller than the error of the physical qubits. With their new results, the researchers were able to demonstrate the scalability of their approach.
Simulation of quantum chemistry
To illustrate the performance of their quantum computer, the researchers used Microsoft to carry out complex quantum chemistry simulations. Specifically, they looked at a chemical reaction in which a catalyst is used to produce chiral molecules, i.e. molecules that cannot be superimposed with their mirror images. The aim was to better understand the reaction mechanism and precisely estimate the energy barrier of the reaction.
For the simulation, the researchers combined their quantum computer with high-performance computers and artificial intelligence. They used Microsoft's Azure Quantum Elements platform –, a cloud platform for solving scientific problems. With their method, the researchers were able to solve the problem with a high degree of accuracy.
The researchers were unable to demonstrate a quantum advantage, as a conventional supercomputer could also solve the problem. However, such tests pave the way for complex quantum chemical calculations using quantum processors, where classical computers fail.
The researchers expect a quantum advantage to be achieved as soon as around 100 logical qubits are available. Microsoft is also planning to apply their methods to other architectures for quantum computers. To this end, they are cooperating with the start-up Atom Computing, for example, which produces qubits from uncharged atoms.
(spa)
