Superconducting Qubit structures for scalable quantum computing

J. Q. You, Jaw-Shen Tsai, Franco Nori

Zhao Na, Liu Jian-She, Li Tie-Fu +1 more

Quantum system based on superconducting circuit is considered as one of the most promising schemes to realize quantum computers due to its controllability, low dissipation and scalability. To implement large scale quantum computation, coherent coupling between qubits is crucial for controlling and transferring quantum states. In this review paper, we summarize the progress of coupled superconducting qubits, including local coupling via capacitance or inductance, multiple qubits coherent interaction through one-dimensional resonator as circuit quantum electrodynamics, and superconducting qubits in a three-dimensional waveguide cavity. Hamiltonians of various coupling schemes are analyzed and classification of these coupling structures is summarized based on the coupling range and tunability.

Matthias Steffen

Mojtaba Hossein Pour Choubi, Mehdi Fardmanesh

Quantum computing has advantages over conventional computing in performing algorithms such as factorization and search. Quantum processors, as a tool for quantum computing, are computing units that consist of qubits as basic elements. There are different approaches toward the implementation of the qubits. The most renowned and applicable of these implementations is based on superconducting qubits. Among various types of superconducting qubits, charge qubits in form of transmons are chosen in this work because of their straightforward fabrication methods and better interfacing and scalability. In this paper, utilizing EPR (Energy Participation Ratio) method, one of the main transmon structures made of High Tcsuperconductor materials, are designed and simulated. Additionally, the effects of some geometry-based parameters of the qubit structure on qubit characteristics such as frequency and anharmonicity are explored. Moreover, the single transmon qubit structure with High Tcsuperconductor transmission lines as readout and control sections are designed and simulated. In addition, due to the Purcell effect, the Purcell filter is added to the designed single qubit structure to reduce the spontaneous emission of the qubit. The results of our simulations are compared with that of the conventional superconductor based transmons.

Michel Devoret

Zhanhong Jin, Shaowei Li, Xinzhe Wang +2 more

As the number of qubits in quantum computing increases, the scalability of existing qubit circuit structures and control systems may become insufficient for large-scale expansion and high-fidelity control. To address this challenge, we propose a behavioral-level model of a superconducting qubit and its control electronics, followed by a co-simulation to evaluate their performance. In this paper, we present the modeling process, simulation procedure, and resulting design specifications for the qubit control system. Our co-simulation approach utilizes MATLAB and Simulink, enabling us to derive critical circuit design specifications, such as the required Digital-to-Analog Converter (DAC) resolution, which should be 8 bits or higher, to achieve high-fidelity control. By taking into account factors such as DAC sampling rates, integral and differential nonlinearities, and filter characteristics, we optimize the control system for efficient and accurate qubit manipulation. Our model and simulation approach offer a promising solution to the scalability challenges in quantum computing, providing valuable insights for the design of large-scale superconducting quantum computing systems.