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 iQuISE program represents a bold step forward to coalesce and cohere the education and research training that will produce a new generation of quantum information researchers for our nation.”

—Claude R. Canizares, Bruno Rossi Professor of Physics, Vice President for Research, and Associate Provost