Southwest Quantum Information and Technology

Adaptive entanglement witnessing with limited local measurement

Presenting Author: Ben Hartley, Harvey Mudd College
Contributing Author(s): Becca Verghese, Eritas Yang, Theresa W. Lynn

We derive and experimentally verify the efficacy of an adaptive entanglement witnessing procedure on two qubits that utilizes local measurements in fewer bases than would be necessary for full state tomography. We begin with six classes of witnesses, {W}, formulated by Riccardi et al (Phys. Rev. A 101, 062319, 2020), and construct 3 additional triplet sets of optimal entanglement witnesses, {W’}, that each require local measurements in two further bases. When applied to computationally generated random two-qubit states, our adaptive procedure is able to witness a significantly more complete set of entangled states than the static {W} witnesses alone. The entangled states which remain undetected have a low concurrence. Using polarization-entangled photons generated via spontaneous parametric down conversion, we demonstrate the behavior of {W} discussed in (reference) and also create and measure two-qubit entangled states that cannot be witnessed by the static method but are detected by our adaptive method. Finally, we discuss future experimental implementations and possible directions to improve our procedure.

(Session 5 : Thursday from 5:00 pm - 7:00 pm)