This book highlights the novel research in quantum memory networking, especially quantum memories based on cold atomic ensembles. After discussing the frontiers of quantum networking research and building a DLCZ-type quantum memory with cold atomic ensemble, the author develops the ring cavity enhanced quantum memory and demonstrates a filter-free quantum memory, which significantly improves the photon-atom entanglement. The author then realizes for the first time the GHZ-type entanglement of three separate quantum memories, a building block of 2D quantum repeaters and quantum networks. The author also combines quantum memories and time-resolved measurements, and reports the first multiple interference of three single photons with different colors. The book is of good reference value for graduate students, researchers, and technical personnel in quantum information sciences.

Dr. Bo Jing

Bo Jing received his PhD from the University of Science and Technology of China in 2019. His research mainly focused on quantum networks with quantum memories, covering highly retrieved quantum memories based on cold atomic ensembles, entanglement of multiple quantum memories, and multi-photon interference. His findings were published in Nature, Nature Photonics, and Physical Review Letters, etc.

Chapter 1 Introduction

1.

1.1. Quantum teleportation

1.2. Connection of two quantum nodes

1.3. Connection of multiple quantum nodes

1.4. Physical realization of quantum network

1.5. Current state of the art for quantum networks

1.6. Thesis structure

Chapter 2 Interaction of single photons and atomic ensembles

2.

2.1. Photon-atom interaction: classical description

2.2. Cavity-enhanced photon-atom interaction: quantum description

2.3. Brief summary

Chapter 3 Preparation of cold atomic ensembles

3.

3.1. Vacuum

3.2. Lasers

3.3. Magnetic field

3.4. Magnetic optical trap

3.5. Polarization gradient cooling

3.6. Cold atomic optical depth and temperature

3.7. Further cooling of cold atoms

3.8. Brief summary

Chapter 4 Highly retrieved quantum memory

4.

4.1. Backgroud

4.2. Principle of DLCZ-type quantum memory

4.3. DLCZ-type quantum memory in free space

4.4. DLCZ-type quanutm memory in a ring cavity

4.5. Quantum memories with atomic initial state

4.6. Brief summary

Chapter 5 Entanglement of three cold atomic ensembles

5.

5.1. Background

5.2. Entanglement between single photons and cold atomic ensembles

5.3. Entagnlement between two cold atomic ensembles

5.4. Hybrid entanglement of three single photons and three cold atomic ensembles

5.5. Entanglement of three cold atomic ensembles

5.6. Efficiency of entanglement generaction and verification

5.7. Brief summary

Chapter 6 Time-resolved interference of three frequency distinguished single photons

6.

6.1. Background

6.2. Single photon source

6.3. HOM interference of two indistinguishable photons

6.4. Interference of two frequency distinguished photons

6.5. Interference of three frequency distinguished photons

6.6. Brief summary

Chapter 7 Entanglement of two cold atomic ensembles via 50 km fibres

7.

7.1. Background

7.2. Experimental principle and setup

7.3. Experimental results

7.4. Brief summary

Chapter 8 Conclusion and prospect

References

Appendix

Acknowledgements

Publications

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