Abstract
Being able to implement effective entanglement distribution in noisy environments is a key step towards practical quantum communication, and long-term efforts have been made on the development of it. Recently, it has been found that the null-result weak measurement (NRWM) can be used to enhance probabilistically the entanglement of a single copy of amplitude-damped entangled state. This paper investigates remote distributions of bipartite and multipartite entangled states in the amplitudedamping environment by combining NRWMs and entanglement distillation protocols (EDPs). We show that the NRWM has no positive effect on the distribution of bipartite maximally entangled states and multipartite Greenberger-Horne-Zeilinger states, although it is able to increase the amount of entanglement of each source state (noisy entangled state) of EDPs with a certain probability. However, we find that the NRWM would contribute to remote distributions of multipartite W states. We demonstrate that the NRWM can not only reduce the fidelity thresholds for distillability of decohered W states, but also raise the distillation efficiencies of W states. Our results suggest a new idea for quantifying the ability of a local filtering operation in protecting entanglement from decoherence.
Highlights
Being able to implement effective entanglement distribution in noisy environments is a key step towards practical quantum communication, and long-term efforts have been made on the development of it
To accomplish the aforementioned quantum information processing tasks, the communicators need to transform the noisy entangled states into maximally entangled pure states in advance. This raises a problem which is of theoretical interest: How can maximally entangled pure states be extracted from shared entangled mixed states by local operations? One solution, at least in principle, is to use entanglement distillation protocols (EDPs) which function as distilling a small number of entangled pure or nearly pure states from a large number of entangled mixed states[1,2,3,4,5]
Our results indicate that the null-result weak measurement (NRWM) is not necessarily helpful to practical entanglement distributions, it is able to increase the amount of entanglement of a single-copy noisy entangled state, and suggest a new approach to quantify the ability of a local filtering operation in protecting entanglement from decoherence
Summary
Being able to implement effective entanglement distribution in noisy environments is a key step towards practical quantum communication, and long-term efforts have been made on the development of it. To accomplish the aforementioned quantum information processing tasks, the communicators need to transform the noisy entangled states into maximally entangled pure states in advance This raises a problem which is of theoretical interest: How can maximally entangled pure states be extracted from shared entangled mixed states by local operations? At least in principle, is to use entanglement distillation protocols (EDPs) which function as distilling a small number of entangled pure or nearly pure states from a large number of entangled mixed states[1,2,3,4,5] This means perfect or nearly perfect entanglement-based quantum information processing would be possible even in noisy environments by utilizing the idea of entanglement purification. A question arises, namely, is the NRWM beneficial to entanglement distribution among distant parties in terms of the efficiency of extracting maximally entangled states, it can improve with a certain probability the entanglement of each source state (initial noisy entangled state) of the EDP? This paper is addressing such an issue
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