Improved entanglement detection with subspace witnesses
Name
PhysRevA.101.012319.pdf
Description
Published version
Size
441.92 KB
Format
Adobe PDF
Checksum (MD5)
46ee81ea51986cbc3d0a286465f225b2
Author(s)
Sun, Won Kyu Calvin
Cappellaro, Paola
Date Issued
January 13, 2020
Journal
Physical review. A.
Publisher
American Physical Society (APS)
Citation
Sun, Won Kyu Calvin, Alexandre Cooper and Paola Cappellaro. "Improved entanglement detection with subspace witnesses." Physical review. A. Volume 101 (2020) © 2020 The Author(s)
Version
Final published version
Abstract
Entanglement, while being critical in many quantum applications, is difficult to characterize experimentally. While entanglement witnesses based on the fidelity to the target entangled state are efficient detectors of entanglement, they in general underestimate the amount of entanglement due to local unitary errors during state preparation and measurement. Therefore, to detect entanglement more robustly in the presence of such control errors, we introduce a 'subspace' witness that detects a broader class of entangled states with strictly larger violation than the conventional state-fidelity witness at the cost of additional measurements, while remaining more efficient with respect to state tomography. We experimentally demonstrate the advantages of the subspace witness by generating and detecting entanglement with a hybrid, two-qubit system composed of electronic spins in diamond. We further extend the notion of the subspace witness to specific genuine multipartite entangled (GME) states detected by the state witness, such as GHZ, W, and Dicke states, and motivate the choice of the metric based on quantum information tasks, such as entanglement-enhanced sensing. In addition, as the subspace witness identifies the many-body coherences of the target entangled state, it facilitates (beyond detection) lower-bound quantification of entanglement via generalized concurrences. We expect that the straightforward and efficient implementation of subspace witnesses would be beneficial in detecting specific GME states in noisy, intermediate-scale quantum processors with a hundred qubits.
MIT Department
Massachusetts Institute of Technology. Department of Nuclear Science and Engineering
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Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1103/physreva.101.012319
