Google’s Sycamore processor installed in a cryostat, recently used to demonstrate quantum purity and the largest quantum chemistry simulation on a quantum computer. Credit: Rocco Ceselin
A team of researchers with Google’s AI Quantum team (working with unspecified collaborators) has performed the largest chemical simulation to date on a quantum computer. In her paper published in the journal Science, the group describes their work and why they believe it was a step forward in quantum computing. Stanford University’s Xiao Yuan has written a perspective piece that explores the potential benefits of using quantum computers for chemical simulations and the work of the team at AI Quantum, published in the same journal issue.
Developing an ability to predict chemical processes by simulating on computers would be a great advantage for chemists – at present they do most of it by trial and error. Prediction would open the door for the development of a wide range of new materials with as yet unknown properties. Unfortunately, today’s computers lack the exponential scaling required for such work. As a result, chemists have hoped that quantum computers will one day take on the role.
Of course, today’s quantum computer technology is not ready to take on such a challenge, but computer scientists hope to get it somewhere in the near future. In the meantime, big companies like Google are investing in research focused on using quantum computers once they are adults. In this new effort, the team at AI Quantum focused their efforts on simulating a simple chemical process – the Hartree-Fock approximation of a real chemical system – in this particular case, a diazene molecule that reacted with hydrogen atoms, which resulted in a changed configuration.
Figuring out how to program Google Sycamore’s quantum system was not difficult – the hard part was figuring out how to make sure the results were accurate – quantum computers are notorious for errors. Validation was the real achievement of the AI Quantum team. They did it by combining the quantum system with a classic computer. It was used to analyze the results given by the Sycamore machine and then to provide new parameters. This process was repeated until the quantum computer worked its way to a minimum value. The team also used two other control systems, both focused on calculating results to detect and repair errors.
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Energy predictions of molecular geometries by the Hartree-Fock model simulated on 10 qubits of the Sycamore processor. Credit: Google
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Left: The energy of a linear chain of hydrogen atoms as the bond spacing between each atom is increased. The fixed line is the Hartree-Fock simulation with a classic computer, while the points are calculated using the Sycamore processor. Right: Two accuracy metrics (infidelity and mean absolute error) for each point calculated using Sycamore. “Raw” is Sycamore’s non-error data. “+ PS” is data of a kind of error reduction that corrects the number of electrons. “+ Purge” is a type of error magnification that corrects for the correct type of state. “+ VQE” is the combination of all error reduction along with varying relaxation of the circuit parameters. Experiments on H8, H10, and H12 show similar performance in error reduction. Credit: Google
Scientists develop first quantum algorithm to characterize sound across large systems
Hartree-Fock on a superconducting qubit quantum computer, Science 28 Aug 2020: Vol. 369, Issue 6507, pp. 1084-1089, DOI: 10.1126 / science.abb9811, science.sciencemag.org/content/369/6507/1084
Google Blog: ai.googleblog.com/2020/08/scal … amental-quantum.html
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Quote: Google launches largest chemical simulation to date on a quantum computer (2020, August 28) Retrieved August 28, 2020 from https://phys.org/news/2020-08-google-largest-chemical-simulation-quantum.html
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