title: Reversing the weak quantum measurement for a photonic qubit.
abstract: We demonstrate the conditional reversal of a weak (partial-collapse) quantum measurement on a photonic qubit. The weak quantum measurement causes a nonunitary transformation of a qubit which is subsequently reversed to the original state after a successful reversing operation. Both the weak measurement and the reversal operation are implemented linear optically. The state recovery fidelity, determined by quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak measurement and discuss the role of the reversing operation as an information erasure.
authors: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea. yskim25@postech.ac.kr
authors: Yong-Su
authors: YS
authors: Kim
authors: Young-Wook
authors: YW
authors: Cho
authors: Young-Sik
authors: YS
authors: Ra
authors: Yoon-Ho
authors: YH
authors: Kim