Faster Gates for Quantum Computing and Simulation in Circuit QED

Juan José García‐Ripoll

Xin Liu, Guangyu Fang, Qinghong Liao +1 more

We propose a two-step approach to realize a multiqubit phase gate in circuit QED beyond the rotating-wave approximation. The multiqubit gate can be implemented in a few nanoseconds, which is much faster than that under the rotating-wave approximation. Also the operation time of the gate is independent of the number of qubits. Due to the absence of the resonator degree of freedom in the effective Hamiltonian, our scheme is insensitive to the initial state of the resonator and immune to the leakage of photons. Numerical simulation shows that the scheme is robust against the main decoherence sources.

Zheng‐Yin Zhao, Run‐Ying Yan, Zhi‐Bo Feng

Construction of optimal gate operations is significant for quantum computation. Here an efficient scheme is proposed for performing shortcut-based quantum gates on superconducting qubits in circuit quantum electrodynamics (QED). Two four-level artificial atoms of Cooper-pair box circuits, having sufficient level anharmonicity, are placed in a common quantized field of circuit QED and are driven by individual classical microwaves. Without the effect of cross resonance, one-qubit NOT gate and phase gate in a decoupled atom can be implemented using the invariant-based shortcuts to adiabaticity. With the assistance of cavity bus, a one-step SWAP gate can be obtained within a composite qubit-photon-qubit system by inversely engineering the classical drivings. We further consider the gate realizations by adjusting the microwave fields. With the accessible decoherence rates, the shortcut-based gates have high fidelities. The present strategy could offer a promising route towards fast and robust quantum computation with superconducting circuits experimentally.

Andrew Houck

N. Cody Jones, James Daniel Whitfield, Peter L. McMahon +4 more

Quantum computers can in principle simulate quantum physics exponentially faster than their classical counterparts, but some technical hurdles remain.We propose methods which substantially improve the performance of a particular form of simulation, ab initio quantum chemistry, on faulttolerant quantum computers; these methods generalize readily to other quantum simulation problems.Quantum teleportation plays a key role in these improvements and is used extensively as a computing resource.To improve execution time, we examine techniques for constructing arbitrary gates which perform substantially faster than circuits based on the conventional Solovay-Kitaev algorithm (Dawson and Nielsen 2006 Quantum Inform.Comput.6 81).For a given approximation error , arbitrary single-qubit gates can be 7

Wolfgang Scherer