We are one step closer to building a computer that could disrupt the world of chemistry, as well as many other fields. A team of researchers at IBM has successfully used their quantum computer IBMQ to accurately simulate the molecular structure of beryllium hydride (BeH2). It is the most complex molecule ever to undergo a full quantum simulation.
Molecular simulation is all about finding the ground state of a compound – its most stable configuration. Sounds simple enough, especially for a small three-atom molecule like BeH2. But to really understand the ground state of a molecule, you have to model how every electron in every atom interacts with all the nuclei of other atoms, including the strange quantum effects that occur on such a small scale. This is a problem that becomes more difficult as the size of the molecule increases.
While today's supercomputers can simulate BeH2 and other simple molecules, they soon become overwhelmed, and chemical modelers – who are trying to invent new compounds for things like better batteries and life-saving drugs – are forced to approximate the behavior of an unknown molecule and then test it in the real world to see if it works as expected.
The promise of quantum computing is to greatly simplify this process by accurately predicting the structure of a new molecule and how it will interact with other compounds. In research published today in the journal Nature (Paywall) – and also available on Arxiv (PDF) – the IBM team has shown that they can use a new algorithm to calculate the ground state of BeH2 on a seven-qubit chip.
In some ways, this is a small step forward. But this is an important step on the road to using quantum computers to achieve increasingly complex molecular simulations, which will eventually lead to important breakthroughs in business.
Even now, as the research team notes in their blog post about the work, IBM offers a free cloud service with access to 16-qubit quantum computers. The more qubits a chip has, that is, the more qubits that can be used to encode data in multiple states at the same time, the greater the computational complexity it should be able to handle. In theory, at least. As we pointed out in 2017 when we presented practical quantum computers as one of the breakthrough technologies, one of the big challenges in designing quantum computers is ensuring that qubits remain in their delicate quantum state long enough to perform calculations. However, the more qubits a chip has, the harder it is for researchers to do this
Still, the day when quantum computers surpass classical machines – a turning point known as quantum supremacy – is fast approaching. Some observers believe that a chip with 50 qubits would be enough to achieve this goal. Although the chemistry community will benefit greatly from these advances, it is not the only field. Quantum computers promise to be the superstars of any optimization problem, which will help drive huge advances in everything from artificial intelligence to how companies deliver packages to customers.