我們提出一個純固態的量子相干糾纏態產生元件，主要是利用超導LC震盪電路（最近實驗已證實其量子效應）與超導磁通量量子位元（flux qubit）的耦合產生相干糾纏態。

We proposed a novel pure electronic (solid state) device consisting of two superconducting LC circuits coupled to a superconducting flux qubit. The entangled coherent states of the two LC modes can be generated through the measurement of the flux qubit states. The interaction of the flux qubit and two LC circuits can be controlled by the external microwave control lines. The geometrical structure of the LC circuits is adjustable and makes a strong coupling between them achievable. This entangled coherent state generator can be realized by using the conventional microelectronic fabrication techniques which increases the feasibility of the experiment.

Abstract i
Abstract in Chinese ii
Acknowledgement in Chinese iii
Contents v
List of figures vii
List of tables viii

1 Introduction 1
1.1 Quantum Entanglement . . . . . . . . . . . . . . . . . . . . . 1
1.2 Entangled Coherent State . . . . . . . . . . . . . . . . . . . . 2
1.3 A Novel Pure Solid State System . . . . . . . . . . . . . . . 2

2 LC Oscillator 7
2.1 Harmonic Oscillating Property of the LC Circuit . . . . . . . 7
2.2 Quantum Harmonic Oscillator . . . . . . . . . . . . . . . . . . 8
2.3 Coherent State . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 The Evidence of the Quantized LC circuit . . . . . . . . . . . 10

3 Superconducting Flux Qubit 14
3.1 Josephson effect . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.2 Josephson Flux Qubit . . . . . . . . . . . . . . . . . . . . . . 18
3.2.1 One Josephson Junction Flux Qubit . . . . . . . . . . 19
3.2.2 Three Josephson Junctions Flux Qubit . . . . . . . . . 20
3.2.3 Four Josephson Junctions Flux Qubit . . . . . . . . . . 22
3.3 Measuring of a Flux Qubit . . . . . . . . . . . . . . . . . . . . 23

4 Entanglement coherent states of two LC circuits 27
4.1 Entangling two Superconducting-LC Coherent Modes . . . . . 27
4.2 Symmetric LC Circuits . . . . . . . . . . . . . . . . . . . . . . 30
4.3 Other entangled coherent states of two LC circuits . . . . . . 30

5 Conclusion 33

A The Interaction Picture 35

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