# Chiral Magnetic Josephson Junction as a Base for Low-Noise Superconducting Qubits

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## Abstract

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## 1. Introduction

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## Abbreviations

CMJ | Chiral Magnetic Josephson |

CME | Chiral Magnetic Effect |

## Note

1 | Possible candidates for the NCS superconductors should thus have a crystalline structure with either the point group O (Li _{2}Pt_{3}B, Mo_{3}Al_{2}C), T point group (e.g. LaRhSi, LaIrSi), or ${C}_{4}$ (La_{5}B_{2}C_{6}), ${C}_{2}$ (UIr), etc. On the other hand, the point groups ${C}_{n\nu}$ with n = 2, 3, 4, 6 (possessed, for example, by the compounds MoS_{2}, MoN, GaN, CePt_{3}Si, CeRhSi_{3}, amd CeIrSi_{3} [7]) correspond to the Lifshitz invariants of the type $\mathit{n}\xb7\mathit{h}\times \mathit{j}$ that do not fit our proposal. |

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**Figure 1.**The Chiral Magnetic Josephson junction: two non-centrosymmetric superconductors (NCSs) are weakly linked by a uniaxial ferromagnet (F). The exchange field $\mathit{h}$ of the ferromagnet, oriented across the link, induces an inversion symmetry-breaking component of the supercurrent (represented by the spiral) in the junction.

**Figure 2.**(

**a**) Fluxonium-type qubit based on conventional Josephson junction inductively shunted by a series of Josephson junctions. The qubit is biased by an external magnetic flux ${\phi}_{\mathrm{ext}}\equiv 2\pi \Phi /{\Phi}_{0}$, where ${\Phi}_{0}$ is the elementary flux quantum. The gate phase offset for a conventional Josephson junction is absent, ${\phi}_{g}=0$. (

**b**) Chiral magnetic qubits based on the Chiral Magnetic Josephson (CMJ) junction are inductively shunted by a series of Josephson junctions. The CMJ junction possesses an internal phase offset ${\phi}_{g}\ne 0$ eliminating the need for an external magnetic flux ${\phi}_{\mathrm{ext}}$.

**Figure 3.**The potential energy (3) of the chiral magnetic qubit with the chiral magnetic Josephson junction possessing the phase offset ${\phi}_{g}=\pi /2$ for various Coulomb charging energies ${E}_{C}$ and inductive energies ${E}_{L}$: (

**a**) ${E}_{C}=0.045{E}_{J}$, ${E}_{L}={E}_{J}$; (

**b**) ${E}_{C}=0.045{E}_{J}$, ${E}_{L}=0.2{E}_{J}$; (

**c**) ${E}_{C}=0.045{E}_{J}$, ${E}_{L}=0.1{E}_{J}$; and (

**d**) ${E}_{C}=0.01{E}_{J}$, ${E}_{L}={E}_{J}$. Lowest eigenstates $|n\rangle $ with $n=0,1,\dots $ are shown along with the numerically computed energy levels ${\epsilon}_{n}$ and the corresponding wavefunctions ${\psi}_{n}\left(\phi \right)$.

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**MDPI and ACS Style**

Chernodub, M.N.; Garaud, J.; Kharzeev, D.E.
Chiral Magnetic Josephson Junction as a Base for Low-Noise Superconducting Qubits. *Universe* **2022**, *8*, 657.
https://doi.org/10.3390/universe8120657

**AMA Style**

Chernodub MN, Garaud J, Kharzeev DE.
Chiral Magnetic Josephson Junction as a Base for Low-Noise Superconducting Qubits. *Universe*. 2022; 8(12):657.
https://doi.org/10.3390/universe8120657

**Chicago/Turabian Style**

Chernodub, Maxim N., Julien Garaud, and Dmitri E. Kharzeev.
2022. "Chiral Magnetic Josephson Junction as a Base for Low-Noise Superconducting Qubits" *Universe* 8, no. 12: 657.
https://doi.org/10.3390/universe8120657