Quantum optimization using variational algorithms on near-term quantum devices
| Autor: | John A. Smolin, Kristan Temme, Jerry M. Chow, Abhinav Kandala, Ivano Tavernelli, Jay M. Gambetta, Lev S. Bishop, Panagiotis Kl. Barkoutsos, Walter Riess, Andreas Fuhrer, Antonio Mezzacapo, Andrew W. Cross, Gian Salis, Nikolaj Moll, Marc Ganzhorn, Daniel J. Egger, Stefan Filipp, Peter Müller |
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| Rok vydání: | 2017 |
| Předmět: |
Quantum Physics
Optimization problem Physics and Astronomy (miscellaneous) Computer science Heuristic (computer science) Materials Science (miscellaneous) FOS: Physical sciences 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Atomic and Molecular Physics and Optics Quantum gate Qubit 0103 physical sciences Quantum system Quantum algorithm Electrical and Electronic Engineering 010306 general physics 0210 nano-technology Quantum Physics (quant-ph) Algorithm Quantum Quantum computer |
| DOI: | 10.48550/arxiv.1710.01022 |
| Popis: | Universal fault-tolerant quantum computers will require error-free execution of long sequences of quantum gate operations, which is expected to involve millions of physical qubits. Before the full power of such machines will be available, near-term quantum devices will provide several hundred qubits and limited error correction. Still, there is a realistic prospect to run useful algorithms within the limited circuit depth of such devices. Particularly promising are optimization algorithms that follow a hybrid approach: the aim is to steer a highly entangled state on a quantum system to a target state that minimizes a cost function via variation of some gate parameters. This variational approach can be used both for classical optimization problems as well as for problems in quantum chemistry. The challenge is to converge to the target state given the limited coherence time and connectivity of the qubits. In this context, the quantum volume as a metric to compare the power of near-term quantum devices is discussed. With focus on chemistry applications, a general description of variational algorithms is provided and the mapping from fermions to qubits is explained. Coupled-cluster and heuristic trial wave-functions are considered for efficiently finding molecular ground states. Furthermore, simple error-mitigation schemes are introduced that could improve the accuracy of determining ground-state energies. Advancing these techniques may lead to near-term demonstrations of useful quantum computation with systems containing several hundred qubits. Comment: Contribution to the special issue of Quantum Science & Technology on "What would you do with 1000 qubits" |
| Databáze: | OpenAIRE |
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