On resonance quantum switch by longitudinal control field and demonstration of Solving Linear Equations by Superconducting Quantum Circuits
Xiaobo Zhu, University of Science and Technology, China
In this talk, I will introduce our recent two progresses on superconducting qubit system.
The first work is about the quantum switch by longitudinal control. In quantum optics and atomic physics, the longitudinal coupling and control between electromagnetic fields and atoms are normally ignored. In artificial systems, e.g., superconducting quantum devices, all directional couplings can be engineered in principle. I will show dynamical switching on or fully off by a longitudinal control field for the resonant coupling between the qubit and the quantized single-mode microwave field, while the qubit always keeps working at the coherence optimal point. This approach suggests a new way to control coupling among qubits and data buses by longitudinal control fields, and can be scaled up to large scale quantum chips without any auxiliary circuit and free of the frequency crowding problem.[1]
The second work is related to the demonstration of HHL quantum algorithm after its inventor Aram Harrow, Avinatan Hassidim and Seth Lloyd. It shows that a quantum computer can solve a N dimensional a system of linear equations in O(logN)time, which is exponentially faster than the best known classical algorithm. We experimentally show this algorithm on a quantum processor with four superconducting qubits to solve a system of 2 × 2 linear equations. Fidelities of output states are higher than 83% for all input states. It indicates the potential of quantum speedup on solving linear equations by superconducting circuits.[2]
[1] arXiv:1605.06747
[2] Demonstration of Solving Linear Equations by Superconducting Quantum Circuits, (In preparation)