- 标题
- 摘要
- 关键词
- 实验方案
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Entanglement in four qubit states: Polynomial invariant of degree 2, genuine multipartite concurrence and one-tangle
摘要： Characterization of the multipartite mixed state entanglement is still a challenging problem. This is due to the fact that the entanglement for the mixed states, in general, is defined by a convex-roof extension. That is the entanglement measure of a mixed state ρ of a quantum system can be defined as the minimum average entanglement of an ensemble of pure states. In this paper, we show that polynomial entanglement measures of degree 2 of even-N qubits X states is in the full agreement with the genuine multipartite (GM) concurrence. Then, we plot the hierarchy of entanglement classification for four qubit pure states and then using new invariants, we classify the four qubit pure states. We focus on the convex combination of the classes whose at most the one of the invariants is non-zero and find the relationship between entanglement measures consist of non-zero-invariant, GM concurrence and one-tangle. We show that in many entanglement classes of four qubit states, GM concurrence is equal to the square root of one-tangle.
关键词： Multipartite entanglement,Genuine multipartite concurrence,Polynomial invariant of degree 2
更新于2025-09-23 15:21:21
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Verifying multipartite entangled Greenberger-Horne-Zeilinger states via multiple quantum coherences
摘要： The ability to generate and verify multipartite entanglement is an important benchmark for near-term quantum devices. We develop a scalable entanglement metric based on multiple quantum coherences and demonstrate experimentally on a 20-qubit superconducting device. We report a state fidelity of 0.5165 ± 0.0036 for an 18-qubit GHZ state, indicating multipartite entanglement across all 18 qubits. Our entanglement metric is robust to noise and only requires measuring the population in the ground state; it can be readily applied to other quantum devices to verify multipartite entanglement.
关键词： quantum coherence,multipartite entanglement,quantum computing,superconducting qubits,GHZ states
更新于2025-09-23 15:19:57
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Construction of genuine multipartite entangled states
摘要： Genuine multipartite entanglement is of great importance in quantum information, especially from the experimental point of view. Nevertheless, it is difficult to characterize genuine multipartite entangled states, because the genuine multipartite entanglement is unruly. There are scattered results on the criteria for genuine multipartite entangled states. We propose another product based on the Kronecker product in this paper. The Kronecker product is a common product in quantum information with good physical interpretation. We mainly investigate whether the proposed product of two genuine multipartite entangled states is still a genuine entangled one. We understand the entanglement of the proposed product better by characterizing the entanglement of the Kronecker product. Then we show the proposed product is a genuine multipartite entangled state in two cases. The results develop nontrivial criteria for a class of genuine multipartite entangled states. One can use such criteria to systematically construct genuine multipartite entangled states of more parties.
关键词： genuine multipartite entanglement,Kronecker product,biseparable states
更新于2025-09-16 10:30:52
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Semi-device-independent characterization of multipartite entanglement of states and measurements
摘要： The semi-device-independent framework allows one to draw conclusions about properties of an unknown quantum system under weak assumptions. Here we present a semi-device-independent scheme for the characterization of multipartite entanglement based around a game played by several isolated parties whose devices are uncharacterized beyond an assumption about the dimension of their Hilbert spaces. Our scheme can simultaneously certify that an n-partite high-dimensional quantum state features genuine multipartite entanglement, and that a joint measurement on n subsystems is entangled. Moreover, it provides a lower bound on the number of entangled measurement operators. These tests are strongly robust to noise, and even optimal for certain classes of states and measurements, as we demonstrate with illustrative examples. Notably, our scheme allows the certification of many entangled states admitting a local model, which therefore cannot violate any Bell inequality.
关键词： quantum systems,Hilbert spaces,semi-device-independent,entangled measurements,multipartite entanglement
更新于2025-09-09 09:28:46