Tunable Coupling Scheme for Implementing High-Fidelity Two-Qubit Gates

Abstract

The prospect of computational hardware with quantum advantage relies critically on the quality of quantum gate operations. Imperfect two-qubit gates is a major bottleneck for achieving scalable quantum information processors. Here, we propose a generalizable and extensible scheme for a twoqubit coupler switch that controls the qubit-qubit coupling by modulating the coupler frequency. Two-qubit gate operations can be implemented by operating the coupler in the dispersive regime, which is non-invasive to the qubit states. We investigate the performance of the scheme by simulating a universal two-qubit gate on a superconducting quantum circuit, and find that errors from known parasitic effects are strongly suppressed. The scheme is compatible with existing high-coherence hardware, thereby promising a higher gate fidelity with current technologies.

Solid-state qubits integrated with superconducting through-silicon vias

“…Such qubits are sufficient for off-chip coupling elements for gate-model quantum computing and are on par with devices being developed for high-coherence annealing 12,35 . This validates an important new capability for the 2-stack and 3-stack architectures 30,36 .…”

Quantum supremacy using a programmable superconducting processor

“…As shown in Fig. 1, each qubit is also connected to its neighbouring qubits using a new adjustable coupler 31,32 . Our coupler design allows us to quickly tune the qubit-qubit coupling from completely off to 40 MHz.…”

Demonstrating a Continuous Set of Two-qubit Gates for Near-term Quantum Algorithms

“…Strong coupling with gmon qubits.-The quantum processors used in this work followed the Sycamore design used in reference [16], with each processor consisting of a chain of four gmon transmon qubits coupled by three transmon qubit couplers. Both the qubit frequencies and their coupling can be independently controlled, providing several advantages over fixed coupling designs [11,17,18]. First, since we can turn off the coupling at any detuning, both qubits may idle and perform single-qubit gates while operating closer to their flux insensitive point.…”