Qiskit Pocket Guide

Chapter 7. Quantum Algorithms

Much like many sophisticated classical algorithms, in the future, we’d like to be able to run a quantum algorithm without knowing all the details about its implementation. Qiskit supports many popular quantum algorithms out of the box. You can simply specify a problem, then choose an algorithm to solve it. In this chapter, we’ll explore Qiskit’s algorithms module and the algorithms this module supports.

Background on Quantum Algorithms

Quantum algorithms are the motivation for most research and investment in quantum computing. The entire fields of quantum error correction, quantum hardware, and quantum software development (including Qiskit) ultimately work toward the common goal of running a useful algorithm on a quantum computer.

With this in mind, you might find it surprising that there are relatively few problems for which we think we could achieve quantum advantage (where a quantum computer outperforms modern classical computers). Finding new quantum algorithms and new ways to apply known algorithms is a very active area of research. Maybe even more surprising is that, of these candidate quantum algorithms, we’re not actually sure some will have a speedup at all (never mind on huge, fault-tolerant computers). But why is this?

To guarantee a speedup over classical methods, we need to be able to directly compare the quantum algorithm to its classical counterpart, and to make a direct comparison, both algorithms must solve exactly the same problem. ...