Purification-based quantum error mitigation of pair-correlated electron simulations
Thomas E. O’Brien, G. Anselmetti, Fotios Gkritsis, Vincent E. Elfving, S. Polla, William J. Huggins, Oumarou Oumarou, Kostyantyn Kechedzhi, Dmitry A. Abanin, Rajeev Acharya, I. L. Aleǐner, R. M. Allen, T. I. Andersen, K. R. Anderson, M. Ansmann, Frank Arute, Kunal Arya, Abraham Asfaw, Juan Atalaya, Joseph C. Bardin, Andreas Bengtsson, Gina Bortoli, Alexandre Bourassa, Jenna Bovaird, L. Brill, Michael Broughton, Bob B. Buckley, David A. Buell, Tim Burger, Brian Burkett, Nicholas Bushnell, Juan Campero, Z. Chen, B. Chiaro, D. Chik, J. Cogan, Roberto Collins, P. Conner, William Courtney, A. L. Crook, Ben Curtin, D. M. Debroy, Sean Demura, Ilya Drozdov, A. Dunsworth, Catherine Erickson, Lara Faoro, Edward Farhi, Reza Fatemi, V. S. Ferreira, Leslie Flores Burgos, Ebrahim Forati, A. G. Fowler, Brooks Foxen, William Giang, Craig Gidney, D. Gilboa, Marissa Giustina, Raja Gosula, Alejandro Grajales Dau, Jonathan A. Gross, Steve Habegger, M. C. Hamilton, M. Hansen, Matthew P. Harrigan, Sean D. Harrington, P. Heu, M. R. Hoffmann, Sabrina Hong, Trent Huang, Ashley Huff, L. B. Ioffe, S. V. Isakov, Justin Iveland, E. Jeffrey, Z. Jiang, C. Jones, Pavol Juhás, Dvir Kafri, Tanuj Khattar, Mostafa Khezri, Mária Kieferová, S. Kim, P. V. Klimov, A. R. Klots, Alexander N. Korotkov, Fedor Kostritsa, John Mark Kreikebaum, David Landhuis, Pavel Laptev, K.-M. Lau, Lily Laws, J. Lee, K. Lee, Brian Lester, Alexander T. Lill, W. Liu, William P. Livingston, Aditya Locharla, F. D. Malone
Abstract
Abstract An important measure of the development of quantum computing platforms has been the simulation of increasingly complex physical systems. Before fault-tolerant quantum computing, robust error-mitigation strategies were necessary to continue this growth. Here, we validate recently introduced error-mitigation strategies that exploit the expectation that the ideal output of a quantum algorithm would be a pure state. We consider the task of simulating electron systems in the seniority-zero subspace where all electrons are paired with their opposite spin. This affords a computational stepping stone to a fully correlated model. We compare the performance of error mitigations on the basis of doubling quantum resources in time or in space on up to 20 qubits of a superconducting qubit quantum processor. We observe a reduction of error by one to two orders of magnitude below less sophisticated techniques such as postselection. We study how the gain from error mitigation scales with the system size and observe a polynomial suppression of error with increased resources. Extrapolation of our results indicates that substantial hardware improvements will be required for classically intractable variational chemistry simulations.