This article describes entangled photon pair generation and its application to quantum communication experiments with the aim of achieving quantum repeaters, which are necessary for global-scale quantum communication networks.
Quantum communication which is our ability to transmission quantum information between remote locations is a primitive operation necessary for a future quantum internet. Quantum communication at its heart relies on establishing entangled links between remote locations which can then be used to teleport quantum data. Typically channel losses limit the distance that photons can be sent without some form of quantum repeater networks which segments the channel into smaller pieces. Entanglement distribution, purification and swapping operations then allows one to create high fidelity entangled pairs between the desired remote locations. Several generations of quantum repeaters have been proposed with dramatically increasing performance but the ultimate network performance is limited by channel losses which are typically fundamental in nature. Here we introduce the concept of quantum multiplexing, which allows us to both minimize the number of photons needed in the entanglement distribution processing but also enhance the quality of the entangled pairs generated. In this presentation we discuss the potential performance gains our quantum multiplexing approach gives.
The realization of a functional quantum repeater is one of the major research goals in long-distance quantum communication. Among the different approaches that are being followed, the one relying on quantum memories interfaced with deterministic quantum emitters is considered as among one of the most promising solutions. In this work, we focus on memory-based quantum-repeater schemes that rely on semiconductor quantum dots for the generation of polarization entangled photons. Going through the most relevant figures of merit related to efficiency of the photon source, we select significant developments in fabrication, processing and tuning techniques aimed at combining high degree of entanglement with on-demand pair generation, with a special focus on the progress achieved in the representative case of the GaAs system. We proceed to offer a perspective on integration with quantum memories, both highlighting preliminary works on natural-artificial atomic interfaces and commenting a wide choice of currently available and potentially viable memory solutions in terms of wavelength, bandwidth and noise-requirements. To complete the overview, we also present recent implementations of entanglement-based quantum communication protocols with quantum dots and highlight the next challenges ahead for the implementation of practical quantum networks.
Quantum networks create a completely new way for communication, and the most important function of a quantum network is to generate long-distance quantum entanglement to serve a number of quantum applications. As the scale of the network expands, in order to establish end-to-end entanglement between two remote nodes, entangled pairs need to be generated and distributed among multiple repeaters along the path from the source to the destination, which requires a specific protocol to negotiate resource allocations and quantum operations among the repeaters. Thus, to realize such remote entanglement distribution in a quantum network, designing a stable and reliable protocol becomes urgent and necessary. In this article, we focus on how to guarantee the generation rate of entangled pairs between any two quantum nodes to meet the requirements of various quantum applications in a large-scale quantum network. We present a connection-oriented entanglement distribution protocol inspired by the connection-oriented communication model in classical networks. Our protocol is located in the network layer of the quantum network to enable end-to-end quantum communication. Three main features are provided by the proposed protocol: 1) it is reliable and can guarantee the successful entanglement generation; 2) it can reduce the influence of quantum decoherence via reducing the latency caused by resource competition; and 3) it can guarantee the rate of generating entanglement between two quantum nodes according to the requirement of quantum applications.