IBM’s Quantum Computer Simulates Largest Molecule

IBM’s quantum computer, IBM Q, has now simulated the largest molecule yet, sparking hope of future drug discoveries.

In the breakthrough, outlined in a research paper published in the scientific journal Nature, IBM researchers used a quantum computer to derive the lowest energy state of a molecule of beryllium hydride. Knowing the energy state of a molecule is a key to understanding chemical reactions.

Molecular simulation is all about finding a compound’s ground state—its most stable configuration. Sounds easy enough, especially for a puny little-old three-atom molecule like BeH2. But in order to really know a molecule’s ground state, you have to simulate how each electron in each atom will interact with all of the other atoms’ nuclei, including the strange quantum effects that occur on such small scales. This is a problem that becomes exponentially harder as the size of the molecule increases.

While today’s supercomputers can simulate BeH2 and other simple molecules, they quickly become overwhelmed. Quantum computers on the other hand, can be used to address electronic-structure problems and problems in materials science and condensed matter physics that can be formulated as interacting fermionic problems, problems which stretch the limits of existing high-performance computers.

Quantum computing

holds a lot of promise because it represents a new way of doing computation with quantum bits, or qubits. Unlike conventional bits, a qubit can be a one or a zero or both. Using these qubits enables machines to make great numbers of computations simultaneously, making a quantum computer very good at certain kinds of processing.

In the course of their experiment, the IBM researchers implemented a novel algorithm that is efficient with respect to the number of quantum operations required for the simulation. Using six qubits of a seven-qubit processor they were able to measure BeH2’s lowest energy state, a key measurement for understanding chemical reactions. While this model of BeH2 can be simulated on a classical computer, IBM’s approach has the potential to scale towards investigating larger molecules that would traditionally be seen to be beyond the scope of classical computational methods, as more powerful quantum systems get built.

“Thanks to Nobel laureate Richard Feynman, if the public knows one thing about quantum, it knows that nature is quantum mechanical. This is what our latest research is proving — we have the potential to use quantum computers to boost our knowledge of natural phenomena in the world,” said Dario Gil, vice president of AI research and IBM Q at IBM Research, in a statement. “Over the next few years, we anticipate IBM Q systems’ capabilities to surpass what today’s conventional computers can do and start becoming a tool for experts in areas such as chemistry, biology, health care, and materials science.”

To help showcase how quantum computers are adept to simulating molecules, developers and users of the IBM Q experience are now able to access quantum chemistry Jupyter Notebook. The open source quantum chemistry Jupyter Notebook allows users to explore a method of ground state energy simulation for small molecules such as hydrogen and lithium hydride.

Chemistry is one example of a broader set of problems that quantum computers are potentially well-suited to tackle. Quantum computers also have the potential to explore complex optimization routines, such as might be found in transportation, logistics, or financial services. They could even help advance machine learning and artificial intelligence, which relies on optimization algorithms.

But today’s quantum computers, however, are severely limited by the sensitivity of their qubits, whose delicate 0-and-1 quantum states can be disrupted by temperature fluctuations or stray electric or magnetic fields. IBM’s quantum computing has, however, raised the bar.

Jerry Chow, the manager of experimental quantum computing for IBM, said his team is currently working to improve the speed of its quantum computer with the aim of reducing the time it takes to run each calculation from seconds to microseconds. He said they were also working on ways to reduce its error rate.

Clearly, the day when quantum computers surpass classical machines—an inflection point known as quantum supremacy—is rapidly approaching. The accomplishment “represents solid progress towards an incredibly important goal” of predicting new molecules’ properties, writes Ryan Babbush, the researcher who led Google’s hydrogen simulation.

Disha Padmanabha
In search of the perfect burger. Serial eater. In her spare time, practises her "Vader Voice". Passionate about dance. Real Weird.