Shadow Tomography of Quantum States: Progress and Prospects

*To request access to the videoconference, please contact physinfo@sfu.ca

Synopsis

The Tripartite Quantum Computing Seminar Series (TQCSS) is jointly organized by SFU, UBC and UVic.

Given an unknown quantum state rho, and a known list of two-outcome measurements E_1,...,E_M, "shadow tomography" is the task of estimating the probability that each E_i accepts rho, by carefully measuring only a few copies of rho.  In 2018, I gave the first nontrivial protocol for this task.  In 2019, Guy Rothblum and I exploited a new connection between gentle measurement of quantum states and the field of differential privacy, to give a protocol that requires fewer copies of rho in some cases, and has the additional advantage of being online (that is, the measurements are processed one at a time).  Huge challenges remain in making shadow tomography practical with near-term devices; extremely recently Huang, Kueng, and Preskill took some promising steps in that direction.  I'll survey these developments and the challenges that remain.