Four-quantum-bit W-state and GHZ-state mixed-state three-body separable method in noise environment

Abstract

The invention provides a four-quantum-bit W-state and GHZ-state mixed-state three-body separable method in a noise environment. The separability is considered from the two aspects of sufficiency and necessity. The method for constructing the entanglement witness can judge the lower bound of entanglement (all entanglement states in the method refer to three-body inseparable states), the method is used as a necessary condition of a criterion. In the derivation of sufficient conditions, a method for constructing a target state by using a three-body separable state with parameters is adopted, andthe upper bound of the separable state is found by using the method. Calculation results show that under the conditions of a four-quantum W state and a four-quantum GHZ state, the obtained three-bodyseparable noise margin is very close to the result under the entanglement witness method. In the mixed state research process of the two methods, the three-body separable noise margin of the mixed state obtained by the method is more accurate than the result obtained by only using the entanglement witness method.

Description

technical field [0001] The invention relates to the field of quantum information processing. The present invention designs a method for separating the three-body of the mixed state of the four-qubit W state and the GHZ state in a noise environment, through which the sufficient conditions and necessary conditions for the three-body separability of the mixed state of the four-qubit W state and the GHZ state can be obtained conditions, thus obtaining its noise margin. Background technique [0002] The entanglement witness method is essentially an observable entanglement witness operator, which is denoted as if the For all separable quantum states ρ s Satisfied and there exists at least one quantum state ρ such that for such Say it witnesses the entanglement of ρ. In practical applications, if the entanglement witness has been obtained, for a quantum state, it is only necessary to calculate Whether the quantum state is entangled or separable can be judged as positi...

AI Technical Summary

Problems solved by technology

[0005] The concept of entanglement witness is not difficult to understand, and the process of using it is also very simple and convenient, but it is not easy to get a suitable entanglement witness as an entanglement criterion

There are generally many types of separation of many-body quantum systems. To construct an accurate entanglement witness needs to know the structural distribution of the system, and the construction process is relatively complicated.

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