Single flux quantum circuits with damping based on dissipative transmission lines

Berry connection from many-body wave functions and superconductivity: Circuit quantization for superconducting qubits and absence of a dissipative quantum phase transition in Josephson junctions

The new superconductivity theory that attributes the $U(1)$ superconductivity phase to a Berry phase arising from many-body wave functions is applied to the circuit quantization for superconducting qubits. The phase-charge duality required for the occurrence of superconductivity in the standard theory becomes irrelevant in the new theory, and the absence of a dissipative quantum phase transition in Josephson junctions is explained. It is shown that a charge-decaying term leads to the compact phase description, and the appearance of Shapiro steps is explained without introducing normal current.

Josephson tunnel junctions with nonlinear damping for RSFQ-qubit circuit applications

We demonstrate that shunting of Superconductor-Insulator-Superconductor Josephson junctions by Superconductor-Insulator-Normal metal (S-I-N) structures having pronounced non-linear I-V characteristics can remarkably modify the Josephson dynamics. In the regime of Josephson generation the phase behaves as an overdamped coordinate, while in the superconducting state the damping and current noise are strikingly small, that is vitally important for application of such junctions for readout and control of Josephson qubits. Superconducting Nb/AlO${_x}$/Nb junction shunted by Nb/AlO${_x}$/AuPd juncti…

可调且非线性增强的光子压力电路中的色散-耗散耦合

Tunable and nonlinearity-enhanced dispersive-plus-dissipative coupling in photon-pressure circuits

该研究通过磁通量可调的色散-耗散光子压力耦合，实现了GHz与MHz电路的非线性增强多光子耦合，展示了费诺型响应和参数不稳定性。

耗散量子电路中Transmon的几何相位

Geometric Phase of a Transmon in a Dissipative Quantum Circuit

本文研究了transmon与超导谐振腔耦合系统在幺正演化及耗散条件下的几何相位，通过对比两种模型揭示了环境引起的退相干、弛豫和衰减对几何相位的修正。

Two-resonator circuit QED: Dissipative Theory

We present a theoretical treatment for the dissipative two-resonator circuit quantum electrodynamics setup referred to as quantum switch. There, switchable coupling between two superconducting resonators is mediated by a superconducting qubit operating in the dispersive regime, where the qubit transition frequency is far detuned from those of the resonators. We derive an effective Hamiltonian for the quantum switch beyond the rotating wave approximation and study the dissipative dynamics within a Bloch-Redfield quantum master equation approach. We derive analytically how the qubit affects the …

Circuit theory for decoherence in superconducting charge qubits

Based on a network graph analysis of the underlying circuit, a quantum theory of arbitrary superconducting charge qubits is derived. Describing the dissipative elements of the circuit with a Caldeira-Leggett model, we calculate the decoherence and leakage rates of a charge qubit. The analysis includes decoherence due to a dissipative circuit element such as a voltage source or the quasiparticle resistances of the Josephson junctions in the circuit. The theory presented here is dual to the quantum circuit theory for superconducting flux qubits. In contrast to spin-boson models, the full Hilbert…