Superconducting phase qubit based on the Josephson oscillator with strong anharmonicity

TL;DR

This paper introduces a superconducting phase qubit based on a radio-frequency SQUID with strong anharmonicity, enabling efficient readout and tunable qubit interactions, advancing quantum computing hardware.

Contribution

It proposes a novel superconducting phase qubit design with high anharmonicity and tunable transition frequency, improving qubit control and readout capabilities.

Findings

Achieves >30% anharmonicity in the qubit potential.

Provides a qubit insensitive to charge noise at the optimal point.

Demonstrates tunable transition frequency for variable qubit coupling.

Abstract

We propose a superconducting phase qubit on the basis of the radio-frequency SQUID with the screening parameter value $\beta_L = (2\pi/\Phi_0)LI_c \approx 1$, biased by a half flux quantum $\Phi_e=\Phi_0/2$. Significant anharmonicity ($> 30%$) can be achieved in this system due to the interplay of the cosine Josephson potential and the parabolic magnetic-energy potential that ultimately leads to the quartic polynomial shape of the well. The two lowest eigenstates in this global minimum perfectly suit for the qubit which is insensitive to the charge variable, biased in the optimal point and allows an efficient dispersive readout. Moreover, the transition frequency in this qubit can be tuned within an appreciable range allowing variable qubit-qubit coupling.