How Quantum Computing Could Remake Chemistry

A lot of what chemists tried while discovering things was based on luck. But trying to find solutions to huge problems like climate change and Covid-19 cannot be on luck alone. Nature's complex structures need a different approach to handle now.?

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Chemists have to predict how molecules will behave under various circumstances, and even with supercomputers, it isn't easy. This is where quantum computers can make the biggest difference.?

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Modeling chemical reactions becomes difficult as they are unable to go beyond a few electrons. It requires a lot of old-fashioned lab work in parallel by chemists. Quantum computers work differently - each quantum bit (qubit) can map onto a specific electron's spin orbitals. Using 'entanglement' to describe electron-electron interactions without approximations becomes possible. Today, quantum computers can model small molecules too, for example, lithium hydride.?

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This existed since the early 20th century when quantum mechanics was used to understanding covalent bonds. But even in the 2000s, bench chemists didn't have the skills to do computing for chemistry. Some groups persisted, though, combining theoretical research with the experimental one.??

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The explosion of data from experimental methods like high-throughput screening is being used to build better chemical models. On large scale, it is being used for drug discovery and material experimentation. But with regular computers, only "coarse-grained" models are possible due to the need to simplify at each step to keep the computer practically able to work. The coarser the data, the more intensive the lab work.

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It is different and allows the modeling of nature as it is. After all, Richard Feynman had said that nature isn't classical, and its simulation would be quantum-mechanical. The power of quantum computers is steadily rising, and the quality and quantity of qubits are going up. Till now, quantum computers have modeled ground and excited states of molecules and modeling of dipole moment in small molecules. Slowly, one day, it will be possible to model for radical species such as molecules with unpaired electrons.?

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It's not possible that one day, chemists would simply plus algorithms into a quantum device and data to be cross-checked in labs. But what may happen is that quantum models will get incorporated as a step in existing processes that rely on classical computers. Regular computers will aid in handling the computationally intensive parts, and quantum models will handle distinct interactions. The former could be an enzyme, a polymer chain, or a metal surface; the latter could be the chemistry in an enzyme pocket.?

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Progress is being made in embedding quantum-electronic structure calculations into classically computing environments. More advances in polymer chains can help tackle plastic pollution one day. The development of recyclable plastics can be speeded up, and waste reduced. And not just that, it will be possible to produce materials like jet fuel with lower carbon footprints too.

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Today's fresh chemists are computer-literate, but the classically built computers are unable to handle even commonplace complexity. By embracing quantum computers, chemistry will get much luckier.?

- Aindri Abhishek Singh

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