Abstract
Realizing long-distance entanglement swapping with independent sources in the real-world condition is important for both future quantum networks and fundamental study of quantum theory. Currently, entanglement swapping over a few tens of kilometers of underground optical fiber has been achieved. However, future applications demand entanglement swapping over longer distances in more complicated environments. We exploit two independent 1-GHz-clock sequential time-bin entangled photon-pair sources; develop several automatic stability controls; and successfully implement a field test of entanglement swapping over an optical fiber link of more than 100 km, including coiled, underground, and suspended optical fibers. Our result verifies the feasibility of such technologies for long-distance quantum networks and for many interesting quantum information experiments.
Highlights
Entanglement swapping [1,2] is a unique feature of quantum physics
We present an implementation of entanglement swapping in an intercity quantum network, which is composed of about 77 km of optical fiber inside the lab, 25 km of optical fiber outside the lab but kept underground, and 1 km of optical fiber suspended in air outside the lab to account for various types of noise mechanisms in the real world
We have demonstrated entanglement swapping with two independent sources 12.5 km apart using optical fiber of 103 km
Summary
By entangling two independent parties, which have never interacted before, entanglement swapping has been used in studies of physics foundations such as nonlocality [1,3] and wave– particle duality [4]. It is a central element in quantum networks [5,6], appearing in the form of quantum relay [7,8,9] and quantum repeater [10,11]. Entanglement swapping and quantum teleportation were realized in both free-space and optical fiber links over a. We present an implementation of entanglement swapping in an intercity quantum network, which is composed of about 77 km of optical fiber inside the lab, 25 km of optical fiber outside the lab but kept underground, and 1 km of optical fiber suspended in air outside the lab to account for various types of noise mechanisms in the real world
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