ABSTRACT
Contents 3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 3.2 Advanced Quantum Communication Schemes. . . . . . . . . . . . . . . . . . . . . . . 47
3.2.1 Scalable Teleportation and Entanglement Swapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2.1.1 Entanglement Swapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.2.1.2 Scalable Teleportation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 3.2.1.3 Long-Distance Quantum Teleportation . . . . . . . . . . . . . 51
3.2.2 Purifying Quantum Entanglement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 3.2.3 A Photonic Controlled NOT Gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
and
3.2.4 Higher Dimensional Entanglement for Quantum Communications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.2.5 Entanglement-Based Quantum Cryptography . . . . . . . . . . . . . . . . 62 3.2.5.1 Adopted BB84 Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 3.2.5.2 An Entanglement-Based Quantum
Cryptography Prototype System . . . . . . . . . . . . . . . . . . . . 64 3.2.6 Toward a Global Quantum Communication
Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 3.2.6.1 Free-Space Distribution of Quantum
Entanglement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 3.2.6.2 Quantum Communications in Space . . . . . . . . . . . . . . . . 73
3.3 Conclusion and Outlook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
3.1 Introduction Quantum communication and quantum computation are novel methods of information transfer and information processing, all fundamentally based on the principles of quantum physics. The performances outdo their classical counterparts in many aspects [1,2]. In almost all quantum communication and quantum computation schemes, quantum entanglement [3] plays a decisive role. In essence, an entangled system can carry all information (e.g., on their polarization properties) only in their correlations, while no individual subsystem carries any information. This leads to correlations that are much stronger than classically allowed [89, 100], which is a powerful resource for information processing. It is therefore important to be able to generate, manipulate, and distribute entanglement as accurately and as efficiently as possible.
