在外场辅助作用下制备光场纠缠相干态及腔量子电动力学的应用

摘要

量子信息理论作为新兴交叉的学科而诞生,无疑是量子力学的又一个辉煌成果,反过来也丰富了量子力学的研究内容,有力地推动了量子理论的发展.量子信息技术可望成为21世纪的重要高新技术,使信息科学从经典时代跃向量子时代.量子信息的实现在理论上已不存在不可逾越的障碍,但要在技术上实现却面临着诸多困难.其中,如何有效地制备、传递和控制量子态,特别是量子纠缠态,便是对量子信息实际应用的一大挑战.该论文专注于量子态的制备,尤其是量子纠缠态的制备这一课题.该论文在理论上集中采用微腔量子电动力学(CQED)的方法,在外加的经典强场直接与微腔中的二能级原子持续作用且经典场与腔场简并时,利用二能级原子与微腔场和外加经典场的大失谐互作用,结合系统的初始态及互作用后对原子态选择测量来制备光场的薛定谔猫态和量子纠缠态,尤其是光场的纠缠相干态.首先,我们讨论了在外场辅助下利用多原子与单模腔场的大失谐互作用产生相干态和各种薛定谔猫态;接着,分别研究在外场辅助下,多原子同时与双模腔场和多原子依次与空间中分立的两个微腔的大失谐互作用来制备光场的纠缠相干态;最后,我们提出一种在双原子与单模腔场的非对称互作用模型中实现原子-光子纠缠及消纠缠的方案.该文的主要创新之处在于:第一,以前无人讨论过这种利用原子同时与微腔场和外加经典驱动场的大失谐互作用制备量子态的模型,因此它是对该研究领域以往工作的推广;第二,与CQED中传统的大失谐互作用模型相比,该文模型在实验上的实现不需要与调速管相连的受经典场驱动的波导向腔中注入相干态,而是使外场直接与微腔中的原子作用,当外场足够强时有可能在较短时间内制备出薛定谔猫态和光场的纠缠相干态,不需要象通常微腔CQED实验中那样极其精确地控制互作用的时间,因此减少了对实验的人为干预.第三,通过原子依次与空间中两个分立的腔场作用,可以产生光场的一系列纠缠相干态,和纠缠相干态的叠加态,这在以往利用CQED制备量子态的方案中还没有讨论过.

目录

文摘

英文文摘

Acknowledgements

CHAPTER1Introduction

1.1 Quantum superpositions and Schrodinger cat states in quantum optics

1.2 Quantum entanglement

1.3 Entanglement swapping

1.4 Thesis outline

1.5 Literature

CHAPTER2State of the art

2.1 Photons

2.1.1 Concept

2.1.2 Experiments

2.1.3 Comments

2.2 Trapped ions

2.2.1 Concept

2.2.2 Experiments

2.2.3 Comments

2.3 Cavity QED

2.3.1 Concept

2.3.2 Experiments

2.3.3 Comments

2.4 Quantum dots

2.4.1 Concept

2.4.2 Experiments

2.4.3 Comments

2.5 Superconducting qubits

2.5.1 Concept

2.5.2 Experiments

2.5.3 Comments

2.6 Solid-state NMR

2.6.1 Concept

2.6.2 Experiments

2.7 Prospectiveness

CHAPTER3 Basics of quantum optics

3.1 Quantization of the electromagnetic field

3.1.1 Discrete single modes

3.1.2 Continuous set of modes

3.1.3 The quantum harmonic oscillator and number states

3.1.4 Quadratures as continuous quantum variables

3.2 Representations of the quantized electromagnetic field

3.2.1 The Heisenberg and the Schrodinger representations

3.2.2 Coherent states

3.2.3 Distinction of pure and mixed states

3.3 Linear optics with the quantized field

3.3.1 Beam splitter transformations

3.4 Review of cavity QED techniques

CHAPTER4 Basics of quantum information

4.1 Discrete-variable entanglement

4.1.1 No-cloning

4.1.2 Bipartite entanglement

4.1.3 How to “witness” bipartite entanglement

4.1.4 Multipartite entanglement

4.1.5 Werner states

4.2 Continuous-variable entanglement

4.2.1 History and motivation

4.2.2 Criteria for bipartite entanglement

4.2.3 Entangled coherent states

CHAPTER5Quantum state generation in dispersive CQED

5.1 Conditional generation of Schrodinger cat states

5.1.1 Introduction

5.1.2 The theoretical model

5.1.3 Generation of Schrodinger cat like states

5.1.4 Conclusion

5.2 Conditional synthesis of entangled coherent states with continuous external pumping

5.2.1 Introduction

5.2.2 The theoretical model

5.2.3 Generation of multipartite entangled states

5.2.4 Conclusion

5.3 Generation of entangled coherent states between two separated cavities

5.3.1 Introduction

5.3.2 The proposed scheme

5.3.3 Practical consideration

5.3.4 Conclusion

5.4 Atom-photon entanglement and disentanglement with asymmetric atom-field dynamics

5.4.1 Introduction

5.4.2 The theoretical model and dynamical properties

5.4.3 Atom-photon entanglement and disentanglement

5.4.4 Conclusion

CHAPTER6 Concluding remarks and outlooks

Bibliography

Publications

Index