https://doi.org/10.1140/epjd/s10053-023-00791-6
Regular Article - Quantum Information
Direct tomography of quantum states and processes via weak measurements of Pauli spin operators on an NMR quantum processor
1
Department of Physical Sciences, Indian Institute of Science Education & Research Mohali, Sector 81 SAS Nagar, 140306, Manauli, Punjab, India
2
Vice Chancellor, Punjabi University Patiala, 147002, Patiala, Punjab, India
Received:
23
June
2023
Accepted:
13
December
2023
Published online:
27
December
2023
In this paper, we present an efficient weak measurement-based scheme for direct quantum state tomography (DQST) and direct quantum process tomography (DQPT) and experimentally implement it on an NMR ensemble quantum information processor without involving any projective measurements. We develop a generalized quantum circuit that enables us to directly measure selected elements of the density matrix and process matrix which characterize unknown quantum states and processes, respectively. This generalized quantum circuit uses the scalar J-coupling to control the interaction strength between the system qubits and the meter qubit. We experimentally implement these weak measurement-based DQST and DQPT protocols and use them to accurately characterize several two-qubit quantum states and single-qubit quantum processes. An extra qubit is used as a meter qubit to implement the DQST protocol, while for the DQPT protocol, two extra qubits (one as a meter qubit and the other as an ancilla qubit) are used.
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© The Author(s), under exclusive licence to EDP Sciences, SIF and Springer-Verlag GmbH Germany, part of Springer Nature 2023. Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
