Główne pojęcia
A method to obtain exact circuit implementation of a matrix inside a block encoding circuit by first converting the matrix into a doubly stochastic matrix, and then expressing it as a linear combination of permutation matrices.
Streszczenie
The paper presents a method for designing quantum circuits by representing a given matrix as a linear combination of permutation matrices. The key steps are:
- Convert the input matrix into a doubly stochastic matrix using diagonal matrices.
- Decompose the doubly stochastic matrix into a linear combination of permutation matrices using Birkhoff's algorithm.
- Implement each permutation matrix as a quantum circuit by decomposing it into a sequence of transpositions, which can be efficiently mapped to multi-controlled X gates.
- Combine the permutation circuits using an ancilla register to implement the overall linear combination.
The paper also discusses several optimization techniques that can be applied to simplify the resulting quantum circuits, such as identifying and removing redundant gates. The authors suggest that this method can be integrated into a full-fledged quantum compiler software.