An alternative to the Lüders generalization of the von Neumann projection is formulated allowing a generalization to measurements represented by positive operator-valued measures. This generalization is based on the notions of non-orthogonal projections and bi-orthonormal systems in Hilbert-Schmidt space, and is closely related to phase-space representations of quantum mechanics. A number of applications will be discussed. It is demonstrated that the alternative projection has a natural interpretation as a representation of the information on the initial state, to be obtained by the measurement.An alternative to the Lüders generalization of the von Neumann projection is formulated allowing a generalization to measurements represented by positive operator-valued measures. This generalization is based on the notions of non-orthogonal projections and bi-orthonormal systems in Hilbert-Schmidt space, and is closely related to phase-space representations of quantum mechanics. A number of applications will be discussed. It is demonstrated that the alternative projection has a natural interpretation as a representation of the information on the initial state, to be obtained by the measurement.

Journal of Physics A Mathematical and GeneralJan 16, 199821 citations

Quantum method of projection

Igor' Victorovich Shirokov, A. A. Drokin

Russian Physics JournalSep 1, 19960 citations

Quantum Predictions Without Nonlocal Projections

D. J. Miller

Springer eBooksJan 1, 19971 citation

A Hybrid Check Polytope Projection Algorithm for ADMM Decoding of LDPC Codes

Qiaoqiao Xia, Xin Wang, Huajun Liu +1 more

The Euclidean projection onto check polytope is the most complicated and time-consuming operation in the alternating direction method of multipliers (ADMM) decoding algorithm for low-density parity-check (LDPC) codes. Existing approximate even-vertex projection algorithm (EVA) can simplify the projection operation, but yields poor decoding performance. By alternately adopting EVA and other accurate projection algorithms, this letter proposes an innovative and simple hybrid projection algorithm (HPA) which can increase the percentage of unuseful projections. Simulation results show that the proposed algorithm can substantially reduce the projection time while achieving better frame error rate (FER) performance when compared with the standard ADMM decoding and the ADMM penalized decoding in the case of avoiding the tedious work of penalty parameter optimization. More importantly, compared with cut search algorithm (CSA), the proposed algorithm can significantly save the average projection time by nearly 80%, and the average decoding time by about 85%.The Euclidean projection onto check polytope is the most complicated and time-consuming operation in the alternating direction method of multipliers (ADMM) decoding algorithm for low-density parity-check (LDPC) codes. Existing approximate even-vertex projection algorithm (EVA) can simplify the projection operation, but yields poor decoding performance. By alternately adopting EVA and other accurate projection algorithms, this letter proposes an innovative and simple hybrid projection algorithm (HPA) which can increase the percentage of unuseful projections. Simulation results show that the proposed algorithm can substantially reduce the projection time while achieving better frame error rate (FER) performance when compared with the standard ADMM decoding and the ADMM penalized decoding in the case of avoiding the tedious work of penalty parameter optimization. More importantly, compared with cut search algorithm (CSA), the proposed algorithm can significantly save the average projection time by nearly 80%, and the average decoding time by about 85%.

IEEE Communications LettersSep 11, 202012 citations

An Alternative Formulation of the Quantum Phase Estimation Using Projection-Based Tensor Decompositions

Marian Stengl

In this paper an alternative version of the quantum phase estimation is proposed, in which the Hadamard gates at the beginning are substituted by a quantum Fourier transform. This new circuit coincides with the original one, when the ancilla is initialized with $\ket{0}$ . With the help of a projection-based tensor decomposition and closed-form expressions of its exponential, this new method can be interpreted as a multiplier coupled to the Hamiltonian of the corresponding target unitary operator. Based on this observation a recursive decomposition is derived.In this paper an alternative version of the quantum phase estimation is proposed, in which the Hadamard gates at the beginning are substituted by a quantum Fourier transform. This new circuit coincides with the original one, when the ancilla is initialized with $\ket{0}$. With the help of a projection-based tensor decomposition and closed-form expressions of its exponential, this new method can be interpreted as a multiplier coupled to the Hamiltonian of the corresponding target unitary operator. Based on this observation a recursive decomposition is derived.

arXiv:2303.05894Mar 10, 20230 citations

An improved quantum projection filter

Qing Zhong Gao, Guofeng Zhang, Ian R. Petersen

arXiv:1909.13524AutomaticaNov 27, 201924 citations

\ket{0}

. With the help of a projection-based tensor decomposition and closed-form expressions of its exponential, this new method can be interpreted as a multiplier coupled to the Hamiltonian of the corresponding target unitary operator. Based on this observation a recursive decomposition is derived.