Peter Zoller: Hybrid Classical-Quantum Algorithms on Programmable Quantum Simulators
0A talk by Peter Zoller at the Workshop on Noisy Intermediate-Scale Quantum Technologies (NISQ), Day 2. NISQ was hosted June 6-7, 2019 by the Joint Center for Quantum Information and Computer Science at the University of Maryland (QuICS). More information about NISQ can be found at https://www.tqcconference.org.
Abstract: Programmable analog quantum simulators have recently emerged as a new paradigm in quantum information processing. In contrast to the universal quantum computer, programmable quantum simulators are non-universal quantum devices with restricted sets of quantum operations, which however can be naturally scaled to a large number of qubits. In this talk we will focus on programmable analog quantum simulators with trapped ions and Rydberg tweezer arrays, and discuss various scenarios and applications of programming these quantum machines. We show results from a theory-experiment collaboration at Innsbruck demonstrating hybrid classical-quantum algorithms where a 20 quit ion analog simulator computes the energy of the ground state of a lattice Schwinger model representing 1D QED. Remarkably, in this experiment we can not only compute the energy on the quantum co-processor but also the algorithmic error (error bar of the energy) by measuring the energy variance. Further examples include theoretical studies where variational algorithms are applied to generate optimal spin squeezed states for given (restricted) quantum resources provided by Rydberg tweezer arrays with application in quantum sensing. We conclude with a discussion of the generic question of cross platform verification of quantum computers and quantum simulators, where the goal is to compare quantum devices on the level of many-qubit wavefunctions in present day experiments.