Quantum Fisher information from randomized measurements
- URL: http://arxiv.org/abs/2105.13164v2
- Date: Tue, 18 Jan 2022 05:58:37 GMT
- Title: Quantum Fisher information from randomized measurements
- Authors: Aniket Rath, Cyril Branciard, Anna Minguzzi, and Beno\^it Vermersch
- Abstract summary: The quantum Fisher information (QFI) is a fundamental quantity of interest in many areas.
We use measurements of the density matrix to construct lower bounds that converge to the QFI.
We present two examples of applications of the method in quantum systems made of coupled qubits and collective spins.
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- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: The quantum Fisher information (QFI) is a fundamental quantity of interest in
many areas from quantum metrology to quantum information theory. It can in
particular be used as a witness to establish the degree of multi-particle
entanglement in quantum many-body-systems. In this work, we use polynomials of
the density matrix to construct monotonically increasing lower bounds that
converge to the QFI. Using randomized measurements we propose a protocol to
accurately estimate these lower bounds in state-of-art quantum technological
platforms. We estimate the number of measurements needed to achieve a given
accuracy and confidence level in the bounds, and present two examples of
applications of the method in quantum systems made of coupled qubits and
collective spins.
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