title: Fundamental bounds in measurements for estimating quantum states.
abstract: Quantum measurement unavoidably disturbs the state of a quantum system if any information about the system is extracted. Recently, the concept of reversing quantum measurement has been introduced and has attracted much attention. Numerous efforts have thus been devoted to understanding the fundamental relation of the amount of information obtained by measurement to either state disturbance or reversibility. Here, we experimentally prove the trade-off relations in quantum measurement with respect to both state disturbance and reversibility. By demonstrating the quantitative bound of the trade-off relations, we realize an optimal measurement for estimating quantum systems with minimum disturbance and maximum reversibility. Our results offer fundamental insights on quantum measurement and practical guidelines for implementing various quantum information protocols.
authors: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.
authors: Hyang-Tag
authors: HT
authors: Lim
authors: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.
authors: Young-Sik
authors: YS
authors: Ra
authors: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.
authors: Kang-Hee
authors: KH
authors: Hong
authors: Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, New Hampshire 03755, USA.
authors: Seung-Woo
authors: SW
authors: Lee
authors: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Korea.
authors: Yoon-Ho
authors: YH
authors: Kim