# CUBIT: Capacitive qUantum BIT

## Abstract

**:**

## 1. Introduction

## 2. Results

## 3. Practical Considerations

#### 3.1. Potential Puddles

#### 3.2. Zero-Point Fluctuations

#### 3.3. Decoherence and Dephasing

#### 3.4. Parametric Amplifiers

## 4. Conclusions & Future Work

## Supplementary Materials

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Graphene/boron nitride/graphene sandwich structure. Wide aluminum contacts are attached across the edges.

**Figure 2.**Illustration of the basic capacitive quantum bit design. The addition of series and parallel extra capacitors adds up to the design flexibility.

**Figure 3.**Illustration of a combined nonlinear quantum capacitance and Josephson junction (JJ) design.

**Figure 4.**Calculation of energy levels of the anharmonic oscillator composed of nonlinear quantum capacitor and linear inductor shown in Figure 2.

**Figure 5.**Variations of qubit frequency and anharmonicity versus operation temperature of the dilution fridge.

**Table 1.**Qubit designs with no series capacitor $S=1\phantom{\rule{3.33333pt}{0ex}}{\mathrm{mm}}^{2}$.

S (${\mathbf{B}}^{2}$) | Design $\mathit{\omega}/2\mathit{\pi}$ (GHz) | T (mK) | ${\mathit{C}}_{\mathit{S}}$ (fF) | Actual $\mathit{\omega}/2\mathit{\pi}$ (GHz) | A (%) |
---|---|---|---|---|---|

1 | 2.5 | 25 | − | 2.29 | 3.9 |

1 | 5 | 25 | − | 4.41 | 6.04 |

1 | 10 | 25 | − | 8.31 | 8.26 |

**Table 2.**Qubit designs with a series capacitor $S=1\phantom{\rule{3.33333pt}{0ex}}{\mathrm{mm}}^{2}$.

S ( ${\mathbf{mm}}^{2}$) | Design $\mathit{\omega}/2\mathit{\pi}$ (GHz) | T (mK) | ${\mathit{C}}_{\mathit{S}}$ (fF) | Actual $\mathit{\omega}/2\mathit{\pi}$ (GHz) | A (%) |
---|---|---|---|---|---|

1 | 2.5 | 25 | 100 | 2.39 | 0.44 |

1 | 5 | 25 | 100 | 4.77 | 0.76 |

1 | 10 | 25 | 1000 | 8.71 | 5.67 |

**Table 3.**Qubit designs with no series capacitor $S=0.1\phantom{\rule{3.33333pt}{0ex}}{\mathrm{mm}}^{2}$.

S (${\mathbf{mm}}^{2}$) | Design $\mathit{\omega}/2\mathit{\pi}$ (GHz) | T (mK) | ${\mathit{C}}_{\mathit{S}}$ (fF) | Actual $\mathit{\omega}/2\mathit{\pi}$ (GHz) | A (%) |
---|---|---|---|---|---|

0.1 | 10 | 25 | − | 6.42 | 11.2 |

0.1 | 15 | 25 | − | 11.1 | 9.02 |

0.1 | 20 | 25 | − | 11.5 | 11.1 |

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**MDPI and ACS Style**

Khorasani, S. CUBIT: Capacitive qUantum BIT. *C* **2018**, *4*, 39.
https://doi.org/10.3390/c4030039

**AMA Style**

Khorasani S. CUBIT: Capacitive qUantum BIT. *C*. 2018; 4(3):39.
https://doi.org/10.3390/c4030039

**Chicago/Turabian Style**

Khorasani, Sina. 2018. "CUBIT: Capacitive qUantum BIT" *C* 4, no. 3: 39.
https://doi.org/10.3390/c4030039