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Conference on Lasers and Electro-Optics

Direct quantum process tomography via measuring sequential weak values

Yosep Kim, Yong‐Su Kim, Sang‐Yun Lee, Sang-Wook Han, Sung Moon, Yoon-Ho Kim, Young‐Wook Cho

Published Jan 1, 2018• 0 citations
Publisher

Abstract

We demonstrate measurement of the sequential weak value of two incompatible observables by making use of two-photon quantum interference. We also demonstrate direct quantum process tomography of a qubit channel using the sequential weak value.
DOI
10.1364/cleo_qels.2018.ff1b.5

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Weak values, emerging from weak measurements in pre- and postselection, exhibit complex-valued properties, enabling the direct characterization of quantum systems. However, conventional weak values do not account for system evolution, restricting their capability to capture quantum dynamical information. To overcome this limitation, we introduce the process weak value (PWV), which incorporates quantum evolution between observables during pre- and postselection. By establishing a connection between PWVs and the matrix elements of unitary operators, we develop a theoretical framework for the direct characterization of quantum processes. Our experimental validation encompasses single-photon and two-photon unitary processes, as well as non-Hermitian parity-time symmetric quantum processes. Compared to standard quantum process tomography, our method reduces the required bases for state preparation and measurements while circumventing complex reconstruction algorithms, enhancing efficiency and scalability. Our PWV formalism opens avenues for broader foundational investigations of weak measurements and enables efficient applications in characterizing sophisticated quantum processes.