12.10 Summary
In this chapter, we looked at QAOA as an example of a quantum technique that does not require fault-tolerant, error-corrected qubits. QAOA is an example of a variational quantum eigensolver that uses the variational principle from physics to find solutions to combinatorial optimization problems, such as Max-Cut.
Variational algorithms have potential value because they can use relatively short-depth circuits in conjunction with classical optimization techniques, such as gradient descent. We introduced the concepts of Hamiltonian and ansatz and showed how expectation allows us to compute an upper bound for eigenvalues.
The chapter concluded with a sober look at the perceived versus actual value of NISQ algorithms. Do you think we should bother, or should we focus our efforts on fault-tolerant, error-corrected qubits?
