[[Quantum counting]] solves a generalization of the search problem. It solves the problem of counting the number of marked entries in an unordered list, instead of just detecting if one exists. Specifically, it counts the number of marked entries in an <math>N</math>-element list, with error <math>\varepsilon</math> making only <math>\Theta\left(\frac{1}{\varepsilon} \sqrt{\frac{N}{k}}\right)</math> queries, where <math>k</math> is the number of marked elements in the list.<ref> | [[Quantum counting]] solves a generalization of the search problem. It solves the problem of counting the number of marked entries in an unordered list, instead of just detecting if one exists. Specifically, it counts the number of marked entries in an <math>N</math>-element list, with error <math>\varepsilon</math> making only <math>\Theta\left(\frac{1}{\varepsilon} \sqrt{\frac{N}{k}}\right)</math> queries, where <math>k</math> is the number of marked elements in the list.<ref> |