6 papers
Generalized matrix nearness problems II
Rongbiao Thomas Wang, Chi-Kwong Li, Lek-Heng Lim
Given a matrix , a matrix nearness problem seeks an that most closely approximates in the sense of minimizing under a variety of constraints on .…
Approximating quantum states by states of low rank
Nathaniel Johnston, Chi-Kwong Li
Given a positive integer k, it is natural to ask for a formula for the distance between a given density matrix (i.e., mixed quantum state) and the set of density matrices of rank a…
Geometry of essential matrix ranges and the Smith-Ward problem for operator systems
Douglas Farenick, Chi-Kwong Li, Sushil Singla
A -tuple of bounded linear selfadjoint operators acting on an infinite-dimensional separable Hilbert space is said to have the Smith-Ward property if the identity map of the ima…
Semigroup automorphisms of total positivity
Projesh Nath Choudhury, Shaun Fallat, Chi-Kwong Li
Totally positive (TP) and totally nonnegative (TN) matrices connect to analysis, mechanics, and to dual canonical bases in reductive groups, by well-known works of Schoenberg, Gant…
Efficient Circuit-Based Quantum State Tomography via Sparse Entry Optimization
Chi-Kwong Li, Kevin Yipu Wu, Zherui Zhang
Many quantum states arising in algorithms and physical systems occupy only a small, structured subset of the exponentially large Hilbert space, yet standard quantum state tomograph…
(Real)linear preservers of multiples of unitaries and matrix pairs with some extremal norm properties
Bojan Kuzma, Chi-Kwong Li, Edward Poon
We determine the structure of linear maps on complex (real) square matrices sending unitary (orthogonal) matrices to multiples of unitary (orthogonal) matrices. The result is used…