On the Harmonic approximation for large Josephson junction coupling charge qubits

Superconducting qubit without Josephson junctions manipulated by the orbital angular momentum of light

Conventional superconducting qubits have used Josephson junctions as an essential part to provide anharmonicity for well-separated energy-level spacings. However, because a superconducting ring without Josephson junctions has intrinsically well-separated energy-level spacings, Josephson junctions are not necessary as long as one can achieve single-qubit operations. We show that the orbital angular momentum of light can be adopted as a qubit-control means and can eliminate the need for Josephson junctions. The feasibility study reveals that the proposed qubit has many advantages over the previo…

Mean-field dynamics of a Bose Josephson junction in an optical cavity

We study the mean-field dynamics of a Bose Josephson junction which is dispersively coupled to a single mode of a high-finesse optical cavity. An effective classical Hamiltonian for the Bose Josephson junction is derived and its dynamics is studied in the perspective of phase portrait. It is shown that the strong condensate-field coupling does alter the dynamics of the Bose Josephson junction drastically. The possibility of coherent manipulating and \textsl{in situ} observation of the dynamics of the Bose Josephson junction is discussed.

In-situ bandaged Josephson junctions for superconducting quantum processors

Shadow evaporation is commonly used to micro-fabricate the key element of superconducting qubits - the Josephson junction. However, in conventional two-angle deposition circuit topology, unwanted stray Josephson junctions are created which contribute to dielectric loss. So far, this could be avoided by shorting the stray junctions with a so-called bandage layer deposited in an additional lithography step, which may further contaminate the chip surface. Here, we present an improved shadow evaporation technique allowing one to fabricate sub-micrometer-sized Josephson junctions together with band…

有限岛之间约瑟夫森结的量子理论

Quantum theory of the Josephson junction between finite islands

针对传统超导约瑟夫森结有效哈密顿量基于无限大岛假设的局限，研究推导了有限尺寸岛间约瑟夫森结的量子化哈密顿量，并提出可通过测量量子比特频率和电荷极化率的修正来验证该理论。

Dissipative phase transition in two-dimensional d-wave Josephson junctions

Quantum dynamics of in-plane Josephson junctions between two d-wave superconducting films is described by the anisotropic XY-model where both, quasiparticle and Cooper pair tunneling terms, appear to be equally non-local. Applying a combination of the weak and strong coupling analyses to this model, we find a compelling evidence of a dissipative phase transition. The corresponding critical behavior is studied and contrasted with that found previously in the conventional (s-wave) Josephson junctions.

弗朗霍费尔图案在原子约瑟夫森结中

Fraunhofer Patterns in Atomic Josephson Junctions

研究通过合成磁场在原子约瑟夫森结中诱导弗朗霍费尔调制，揭示中性超流体的干涉机制及约瑟夫森涡旋在电流分布中的作用，拓展了物质波电路的研究方向。