Quantum optimal control is a powerful tool for designing a pulse that executes a specified gate, i.e., a unitary transformation in quantum computation. If we consider qubits characterized by different spectroscopic properties, we may design a pulse that executes a specified gate on a specified qubit (
S qubit) with the inclusion of neighboring qubits (
B qubits) but does not explicitly include the other qubits. In this situation, first we introduce sets of reduced time-evolution operators associated with the
S and
B qubits. Then, we apply quantum optimal control to these sets to design optimal pulses that could selectively execute the specified gate on the
S qubit while actively removing the effects of the pulse on the
B qubits, which would lead to a scalable pulse-design procedure. The present pulse design is applied to the quantum computation proposed by DeMille with the aim of executing the Hadamard and controlled-not gates on the
S qubits while actively suppressing the pulse-induced population transitions of the
B qubit states. The numerical results illustrate high fidelity even after introducing the extra qubits that are not included in the pulse design.
In the preparations of superconducting qubits, circuit design is a vital process because the parameters and layout of the circuit not only determine the way we address the qubits, but also strongly affect the qubit coherence properties. One of the most important circuit parameters, which needs to be carefully designed, is the mutual inductance among different parts of a superconducting circuit. In this paper we demonstrate how to design a gap-tunable flux qubit by layout design and inductance extraction using a fast field solver FastHenry. The energy spectrum of the gap-tunable flux qubit shows that the measured parameters are close to the design values.
Superconducting qubits represent a highly promising and scalable quantum hardware technology. The design of these qubits follows a typical microwave circuit design process, where the circuit encompasses multiple resonance frequencies associated with both the resonators and the qubits. Chip design involves the meticulous engineering of resonators and qubits to align the circuit’s various frequencies with predefined values. Additionally, adjusting the coupling between resonators and qubits is essential to meet specific quantum parameters. As the demand for scaling to thousands of qubits grows, it becomes imperative to incorporate systematic engineering and design automation. In this article, we will explore the present requirements for electronic design automation (EDA) that shall enable the design of future superconducting quantum computers.