Generalized quantum singular value transformation with application in quantum conjugate gradient least squares algorithm
*Yu-Qiu Liu (School of Mathematics and Statistics, Wuhan University)
Hefeng Wang (Department of Applied Physics, School of Science, Xi’an Jiaotong University)
Hua Xiang (School of Mathematics and Statistics, Wuhan University)
Quantum signal processing (QSP) and generalized quantum signal processing (GQSP) are essential tools for implementing the block encoding of matrix functions. The achievable polynomials of QSP have restrictions on parity, while GQSP eliminates these restrictions. But GQSP only constructs functions of unitary matrices. In this paper, we further investigate GQSP and extend it to general matrices. Compared with the quantum singular value transformation (QSVT), our proposed method relaxes the requirements on the parity of polynomials. We refer to this extension as generalized quantum singular value transformation (GQSVT). Subsequently, by utilizing the relationship between generalized matrix functions and standard matrix functions, we propose a classical-quantum hybrid quantum conjugate
gradient least squares (CGLS) algorithm using GQSVT.