Quantum Networking

Quantum networks build on entanglement and quantum measurement to achieve tasks that are beyond the reach of classical systems. Using quantum effects, we can detect the presence of eavesdroppers, raise the sensitivity of scientific instruments such as telescopes, or teleport quantum data from one location to another. Long-distance entanglement can be used to execute important tasks such as Byzantine agreement and leader election in fewer rounds of communication than classical systems, improving the efficiency of operations that are critical in distributed systems.

Table of Contents:
Notations xiii Acknowledgements xv Introduction xix Chapter 1 Overview 1 1.1 Introduction 2 1.2 Quantum information 4 1.3 Quantum repeaters 10 1.4 Network architectures 15 1.5 Conclusions 20 Part 1 Fundamentals 23 Chapter 2 Quantum Background 25 2.1 Introduction 26 2.2 Schrodinger's equation 28 2.3 Qubits 29 2.4 Manipulating qubits 41 2.5 Bell pairs 47 2.6 The no-cloning theorem 53 2.7 Conclusion 54 Chapter 3 Networking Background 55 3.1 Concepts 56 3.2 Challenges in scaling up networks 63 3.3 Design patterns 65 3.4 The Internet 75 3.5 Conclusion 77 Chapter 4 Teleportation 79 4.1 The basic teleportation operation 79 4.2 Experimental demonstration of teleportation 82 4.3 State machines for teleportation 84 4.4 Teleporting gates 86 4.5 Conclusion 88 Part 2 Applications 91 Chapter 5 Quantum Key Distribution 93 5.1 QKD and the purpose of cryptography 94 5.2 BB84: single-photon QKD 97 5.3 E91: entanglement-based protocol 100 5.4 Using QKD 101 5.5 Existing QKD networks 105 5.6 Classical control protocols 109 5.7 Conclusion 111 Chapter 6 Distributed Digital Computation and Communication 113 6.1 Useful distributed quantum states 114 6.2 Coin flipping 118 6.3 Leader election 119 6.4 Quantum secret sharing 121 6.5 Byzantine agreement 126 6.6 Client-server and blind computation 128 6.7 Conclusion 130 Chapter 7 Entangled States as Reference Frames 131 7.1 Qubits in the environment 131 7.2 Distributed clock synchronization 135 7.3 Very long baseline optical interferometry 141 7.4 Conclusion 145 Part 3 Lines of Repeaters 147 Chapter 8 Physical Entanglement and Link-Layer Protocols 149 8.1 Creating entanglement using light 149 8.2 Memory and transceiver gubits 156 8.3 Link structure 161 8.4 State machines and protocol interactions 163 8.5 Managing density matrices in distributed software 164 8.6 Examples 169 8.7 Conclusion 173 Chapter 9 Purification 175 9.1 Measurement revisited 175 9.2 Basic purification 177 9.3 Scheduling purification 185 9.4 State machines and protocol interactions 187 9.5 More complex purification protocols 190 9.6 Experimental demonstrations 192 9.7 Conclusion 193 Chapter 10 Purfication and Entanglement Swapping-Based Repeaters 195 10.1 Hardware architectures 195 10.2 Getting from here to there 197 10.3 Nested purification session architecture 203 10.4 State machines and protocol interactions 206 10.5 Putting it all together 208 10.6 Considerations in the design of a simulator 215 10.7 Conclusion 217 Chapter 11 Quantum Error Correction-Based Repeaters 219 11.1 Quantum error correction 220 11.2 CSS repeaters 223 11.3 Surface code repeaters 230 11.4 Conclusion 235 Chapter 12 Finessing the Key Limitations 237 12.1 Quasi-asynchronous 238 12.2 Memoryless 244 12.3 Summary: comparing quantum communication approaches 247 12.4 Conclusion 251 Part 4 Networks of Repeaters 253 Chapter 13 Resource Management and Multiplexing 255 13.1 Simulated network and traffic 256 13.2 Simulations 259 13.3 Conclusion 263 Chapter 14 Routing 265 14.1 Introduction 265 14.2 Difficulties: differences between quantum and classical networks 267 14.3 Problems and solutions 268 14.4 Simulation and results 270 14.5 Conclusion 283 Chapter 15 Quantum Recursive Network Architecture 285 15.1 Review: network architecture 286 15.2 Recursive quantum requests 288 15.3 Implementing recursion in quantum networks 294 15.4 Example 295 15.5 Conclusion 298 Chapter 16 Coda 301 16.1 Future development 301 16.2 Open problems 303 16.3 Further readings for depth 304 16.4 Further readings for breadth 305 16.5 Final thoughts 307 Bibliograpy 309 Index 331