Superconducting RF nanoelectronic devices exhibit a considerable potential for application in future electronics. Josephson effect based devices allow generation, detection, mixing, and parametric amplification of high-frequency signals up into the terahertz region and exhibit high sensitivity, low energy consumption, and small size. Traveling-wave devices can be realized with distributed Josephson junctions. Nonlinear lumped-element circuits can be realized that are small enough so that the circuit dynamics are governed by quantum mechanics. This allows to generate two-photon coherent states and entangled states and will open the door for quantum information processing. Nanotechnological fabrication techniques and the availability of novel materials give a strong impact on the development of novel Josephson-effect-based devices and systems. An overview over the physical principles and the possible applications of nanoelectronic RF Josephson devices is presented.
In this paper, we analyse the properties of an electrical circuit containing Josephson junctions in series. Our approach is looking at the quantum mechanical phase di erence between each pair of superconducting electrodes. Since the di erential equations modelling the behaviour of this arrangement are nonlinear, we mostly work with numerical methods in MATLAB to obtain the solutions. From this point we will proceed with investigating the IV-characteristics and frequency dependent transmission of signals in the circuit when driven by DC and AC current.
Time-dependent electromagnetic drives are fundamental for controlling complex quantum systems, including superconducting Josephson circuits. In these devices, accurate time-dependent Hamiltonian models are imperative for predicting their dynamics and designing high-fidelity quantum operations. Existing numerical methods, such as black-box quantization (BBQ) and energy-participation ratio (EPR), excel at modeling the static Hamiltonians of Josephson circuits. However, these techniques do not fully capture the behavior of driven circuits stimulated by external microwave drives, nor do they include a generalized approach to account for the inevitable noise and dissipation that enter through microwave ports. Here, we introduce numerical techniques that leverage classical microwave simulations, efficiently executable in finite-element solvers, to obtain the time-dependent Hamiltonian of microwave-driven superconducting circuits with arbitrary geometries under charge, flux, or mixed electromagnetic modulation. Importantly, our techniques do not rely on a lumped-element description of the superconducting circuit, in contrast to previous approaches to tackling this problem. We demonstrate the versatility of our approach by characterizing the driven properties of realistic circuit devices in complex electromagnetic environments, including coherent dynamics due to charge and flux modulation, as well as drive-induced relaxation and dephasing. Our techniques offer a powerful toolbox for optimizing circuit designs and advancing practical applications in superconducting quantum computing.
Summary A new engineering discipline called ‘quantum technology’ is emerging. Nanotechnology and cryotechnology enable engineers to develop devices and integrated circuits in which quantum phenomena have dominant sway. Macroscopic finite‐state ‘artificial atoms’ are realized exploiting superconductive Josephson effect, and these ‘atoms’ exchange microwave photons in superconductive microwave circuits. The achievements of cavity quantum electrodynamics in quantum optics are mimicked in the microwave frequency range. The new technology is dubbed circuit quantum electrodynamics. This paper tries to call the attention of engineers majoring in circuit theory and design on the challenges they face in designing quantum circuits. Modeling and simulation of quantum circuit components are reviewed. Approximate closed quantum system models as well as more accurate open system models are introduced in the case of single quantum devices and composite quantum systems. The effects of amplitude damping and phase damping are illustrated by simulation. The role of classical resistors in quantum circuits is investigated. Special attention is given to the almost standardized technology developed for superconductive microwave quantum circuits. Open problems are identified that circuit designers face in developing computer‐aided‐design tools for quantum circuits. Copyright © 2017 John Wiley & Sons, Ltd.
As superconducting circuits emerge as a leading platform for scalable quantum information processing, building comprehensive bridges from the foundational principles of macroscopic quantum phenomena to the architecture of modern quantum devices is increasingly essential for introducing new researchers to the field. This tutorial provides a self-contained, pedagogical introduction to superconducting quantum circuits at the undergraduate level. Beginning with an overview of superconductivity and the Josephson effect, the tutorial systematically develops the quantization of microwave circuits into the framework of circuit quantum electrodynamics (cQED). The transmon qubit is then introduced as a state-of-the-art application, with a detailed derivation of its Hamiltonian and its interaction with control and readout circuitry. The theoretical formalism is consolidated through a numerical simulation of vacuum Rabi oscillations in a driven transmon-resonator system, a canonical experiment that demonstrates the coherent energy exchange characteristic of the strong coupling regime. This work serves as a foundational guide and first point of contact, equipping students and researchers with the conceptual and mathematical tools necessary to understand and engineer superconducting quantum hardware.
We propose a superconducting circuit based on the Bloch transistor, a quantum device consisting of two small-capacitance Josephson junctions, connected in series and having a small superconducting island in between. This device is driven by two dc electrical sources controlling Josephson oscillations of frequency
fJ=2eVJ/h, related to the average transistor voltage
VJ, and Bloch oscillations of frequency
fB=IB/2e, related to the average current
IB injected into the transistor island. We show that due to the Bloch transistor properties, these two types of oscillations are coupled and can mutually phase-lock, i.e.,
fJ=fB. This leads to the formation of a current step on the current-voltage curve at
IB=2efJ, which is similar to the dual Shapiro step, appearing under microwave irradiation of frequency
f on the current-voltage curve of a small Josephson Junction at current
I=2ef. Moreover, the Bloch transistor transconductance
IB/VJ takes the fundamental value of
1/RQ, where
RQ=h/4e2 is the resistance quantum. The obtained results pave the way to an alternative quantum standard of resistance, based on the superconducting circuit and operating without applying a strong magnetic field.