# Realization of Quantum Swap Gate and Generation of Entangled Coherent States

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## Abstract

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## 1. Introduction

## 2. Swap Gate for Photonic Qubits

## 3. Preparation of Entangled Coherent State

## 4. Criteria of Nonclassicality

#### 4.1. Antibunching

#### 4.2. Squeezing

## 5. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) The concrete qutrit level structure and corresponding transitions.; (

**b**) SC coplanar waveguide resonators connected by a $\Lambda $-type SC flux qutrit (coupler).

**Figure 2.**Fidelity of swap gate vs $\kappa /g,$ where ${\kappa}_{1}={\kappa}_{2}=\kappa ,{g}_{1}={g}_{2}=g$.

**Figure 6.**Under short-term condition ${g}_{2}\left(0\right)$ with respect to the parameter $t,\text{}\mathrm{where}\alpha =0.1$.

**Figure 7.**Under long-term condition ${g}_{2}\left(0\right)$ with respect to the parameter $t,\text{}\mathrm{where}\text{}\alpha =0.1$.

**Figure 8.**Under short-term condition antibunching effect ${g}_{2}\left(0\right)$ vs $t,\text{}\mathrm{where}\text{}\alpha =0.1$.

**Figure 9.**Under long-term condition antibunching effect ${g}_{2}\left(0\right)$ vs $t,\text{}\mathrm{where}\text{}\alpha =0.1$.

**Figure 10.**Intermodal squeezing of the symmetric superposition state of two coherent states with respect to the dimensionless parameter $t,\text{}\mathrm{where}\text{}\alpha =0.1$.

**Figure 11.**Intermodal squeezing of the antisymmetric superposition state of two coherent states with respect to the dimensionless parameter $t,\text{}\mathrm{where}\text{}\alpha =0.1$.

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**MDPI and ACS Style**

Zhang, Z.; Jiang, X.; Tang, S.
Realization of Quantum Swap Gate and Generation of Entangled Coherent States. *Symmetry* **2022**, *14*, 1951.
https://doi.org/10.3390/sym14091951

**AMA Style**

Zhang Z, Jiang X, Tang S.
Realization of Quantum Swap Gate and Generation of Entangled Coherent States. *Symmetry*. 2022; 14(9):1951.
https://doi.org/10.3390/sym14091951

**Chicago/Turabian Style**

Zhang, Ziqiu, Xi Jiang, and Shiqing Tang.
2022. "Realization of Quantum Swap Gate and Generation of Entangled Coherent States" *Symmetry* 14, no. 9: 1951.
https://doi.org/10.3390/sym14091951