Abstract
We propose the use of hybrid entanglement in an entanglement swapping protocol, as means of distributing a Bell state with high fidelity to two parties. The hybrid entanglement used in this work is described as a discrete variable (Fock state) and a continuous variable (cat state super- position) entangled state. We model equal and unequal levels of photonic loss between the two propagating continuous variable modes, before detecting these states via a projective vacuum-one-photon measurement, and the other mode via balanced homodyne detection. We investigate homodyne measurement imperfections, and the associated success probability of the measurement schemes chosen in this protocol. We show that our entanglement swapping scheme is resilient to low levels of photonic losses, as well as low levels of averaged unequal losses between the two propagating modes, and show an improvement in this loss resilience over other hybrid entanglement schemes using coherent state superpositions as the propagating modes. Finally, we conclude that our protocol is suitable for potential quantum networking applications which require two nodes to share entanglement separated over a distance of , when used with a suitable entanglement purification scheme.
Highlights
The future of large-scale quantum communications will almost certainly involve distribution and manipulation of entangled pairs of photons within a quantum network; such a quantum network is likely to include small clusters of quantum processors which may require shared entanglement, and could be connected to other network clusters, potentially via satellite communications [1,2,3]
Performing entanglement swapping (ES) to share entanglement enhances the secrecy and security of the post-entangled state shared between Alice and Bob; if an adversary, Eve, were to measure modes B and D, she gains no useful information on states A and C, and by carrying out this measurement Eve has assisted Alice and Bob in sharing an entangled state [24]
continuous variables (CVs) systems typically pose the advantage of high success probability, whereas discrete variables (DVs) are often robust against lossy channels; an advantage could be gained from using both CV and DV states in what is referred to as a hybrid entanglement scheme [34], and will be investigated in this work
Summary
The future of large-scale quantum communications will almost certainly involve distribution and manipulation of entangled pairs of photons within a quantum network; such a quantum network is likely to include small clusters of quantum processors (perhaps in a local network of quantum computers) which may require shared entanglement, and could be connected to other network clusters, potentially via satellite communications [1,2,3]. In ES, there exist two parties, Alice and Bob, each of whom begin the protocol with a separately entangled pair of photons, AB and CD, respectively They each send half of their entangled pair (i.e. modes B and D) to a central location, where these propagating modes are mixed at a 50 : 50 beam-splitter, before subsequently being measured, as described in the schematic of figure 1. This paper is organized as follows: in §2, we introduce our proposed ES protocol, as well as our model for photonic losses in the propagating modes, and the detection methods used; we extend this model for loss, and include averaged unequal losses between modes B and D, in §3; in §4, we show that, following our proposed ES protocol, Alice and Bob can share a Bell state of high fidelity, when allowing for low levels of equal and unequal losses, as well as.
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