Scientists in Sweden have successfully managed to use a quantum computer to solve simple chemistry problems, as a proof-of-concept for more advanced calculations.
Currently, conventional supercomputers are used in quantum chemistry to help scientists learn more about chemical reactions, which materials can be developed and the characteristics they have.
But these conventional computers have a limit to the calculations they can handle. It is believed quantum computers will eventually be able to handle extremely complicated simulations, 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.
Comparing conventional and quantum results
In the new study by Chalmers University, scientists aimed to resolve this noise issue through a method called reference-state error mitigation.
This method involves finding a “reference state” by describing and solving the same problem on both a conventional and a quantum computer.
The reference state is a simpler description of a molecule that can be solved by a normal computer. By comparing the results from both computers, the scientists were able to estimate the scale of error the quantum computer had in its calculation.
The difference between the two computers’ results for the simpler reference problem was then applied to correct the quantum computer’s solution for the original, more complex problem.
This method allowed the scientists to calculate the intrinsic energy of small example molecules such as hydrogen on the university’s quantum computer.
Associate professor Martin Rahm – who led the study – believes the result is an important step forward that can be used to improve future quantum-chemical calculations.
“We see good possibilities for further development of the method to allow calculations of larger and more complex molecules, when the next generation of quantum computers are ready,” Rahm said.
Research is happening around the world to fix the problems limiting the development of more advanced quantum computers.
Earlier this month, Tyndall’s Prof Peter O’Brien told about his group’s work in addressing a key challenge in quantum technology and how quantum communications will make eavesdropping ‘impossible’.