May 5: Dr. Jeongwan Haah (MIT) on “Sample-optimal tomography of quantum states”

Title: Sample-optimal tomography of quantum states
Location: 26-214, Thursday May. 5, Noon-1pm. Pizza at 11:45!
(Feel free to bring your own cup and plate)

Abstract:  It is a fundamental problem to decide how many copies of an unknown mixed quantum state are necessary and sufficient to determine the state. Previously, it was known only that estimating states to error in infidelity δ required O( dr^2 / δ^2 ) copies for a d-dimensional density matrix of rank r. Here, we give a theoretical measurement scheme (POVM) that requires O(dr/δ) ln(d/δ) copies of ρ to error δ in infidelity, and a matching lower bound up to logarithmic factors. We also prove that for independent (product) measurements, Ω(dr^2 / δ^2 ) / ln(1/δ) copies are necessary in order to achieve error δ in infidelity.

“The students in MIT’s new NSF training program will be encouraged to cross disciplines, and develop a common fellowship with their peers. We will also address training for post-academic jobs directly by connecting students to government and industrial members of the iQuISE Consortium.”

—Seth Lloyd, Co-Director, iQuISE, and Professor of Mechanical Engineering and Professor of Engineering Systems