Architecture For Quantum Networks Based On Photons And Ions

In the20th century, quantum mechanics is undoubtedly the most fascinated science in the field of physics. It is counter-intuitive, but perfectly matches with experiments. With the development of quantum mechanics, it derives a series of interdisciplines. Quantum information is one of the most popular field. The key idea of quantum in-formation is to encode the information to quantum state. By use of the superposition property of quantum state, we can realize some tasks that classical information science can not do. During some task, we need to operate quantum state, including preparation, transmission, rotation, memory, and measurement.To carry out quantum operations, we need one or more quantum systems. Now. one of the most popular system include:optics system, trapped ions system, neutral atoms system, quantum dot system, NV center system, superconducting circuit system, nuclear magnetic resonance system, cavity QED system, cavity opto-mechanics. Among these systems, optics system possesses excellent transmission performance and easy qubit operations. Trapped ions system exhibits long coherence time and strong interaction.In this thesis, we focus on these two systems. We briefly introduce the fundamen-tal principles of these two systems, and mainly discuss the architecture for quantum networks based on photons and ions. The main results are listed as below:1. multiuser to multiuser entanglement distribution based on1550nm polarization-entangled photons:Telecom-band polarization-entangled photon-pair source have been widely used in a number of quantum communication experiments due to its acceptable transmission loss. Here, we set up an entanglement distributor based on telecom-band polarization-entangled photons and wavelength division multiplex (WDM). We employ beamlike-type spontaneous parametric down-conversion to prepare telecom-band polarization-entangled photons. The most significant advantage of this source is that it’s quite suit-able to multi-node quantum networks schemes. We demonstrate experimentally that the entanglement source’s fidelity and entanglement concurrence is both greater than95%, and after optical signal transmission through long-distance fiber, the entanglement concurrence almost remains unchanged. In addition, we also demonstrate multiuser-to-multiuser entanglement distribution with WDMs. The entanglement concurrences still remain unchanged. Multiuser-to-multiuser entanglement distribution source also shows non-local due to the fact that it violates CHSH inequality. Lastly, as an application of our entanglement distribution source, we verify we can extract the quantum secret keys from it, and compute the quantum secret key rates. 2. entanglement protection based on non-local non-Markovian environment:Photons suffer from various sorts of decoherence mechanisms in the transmission process, so we need some way to protect photons’coherence during the transmission. Here, we demonstrate experimentally a photonic open system can employ the informa-tion initially held by its environment. The photonic open system present Markovian effects through local system-environment interactions, namely, the photons lose their coherence. But initial correlations in a composite environment lead to nonlocal dynam-ics which show non-Markovian effect, namely, the photons coherence can revival. We demonstrate that we can control this open system’s dynamics by changing initial corre-lation. In turn, we also demonstrate that we can use photonic open system to probe the initial correlations in the composite environment. Lastly we demonstrate that we are able to protect the photonic system against decoherence by changing the local system-environment dynamical configuration.3. quantum networks based on photons and ions:The key idea of quantum networks is how to coherently transfer quantum infor-mation between matter qubit and flying qubit. Here we propose a scheme, based on current experimental techniques, can efficiently transfer quantum information between different ions in a linear ion crystal through phonon mode, and between ion embedded in cavity and photons through strong ion-cavity coupling. So we can transfer some ion internal qubit in a linear ion crystal to any ion internal qubit in another linear ion crystal, or distribute entanglement between them. Lastly, we estimate the success probability based on this scheme.