Single-flux-quantum-based Qubit Control with Tunable Driving Strength

TL;DR

This paper introduces a tunable control scheme for single-flux-quantum (SFQ) circuits that enhances qubit gate precision by allowing continuous adjustment of driving strength, reducing errors and leakage in superconducting quantum processors.

Contribution

The authors propose a novel pulse generator circuit enabling continuous tuning of SFQ pulse driving strength, improving gate fidelity and control flexibility in superconducting qubits.

Findings

Reduces leakage to unwanted levels in SFQ-based gates

Decreases Clifford gate errors by over an order of magnitude

Provides a tunable control scheme for SFQ pulse driving strength

Abstract

Single-flux-quantum (SFQ) circuits have great potential in building cryogenic quantum-classical interfaces for scaling up superconducting quantum processors. SFQ-based quantum gates have been designed and realized. However, current control schemes are difficult to tune the driving strength to qubits, which restricts the gate length and usually induces leakage to unwanted levels. In this study, we design the scheme and corresponding pulse generator circuit to continuously adjust the driving strength by coupling SFQ pulses with variable intervals. This scheme not only provides a way to adjust the SFQ-based gate length, but also proposes the possibility to tune the driving strength envelope. Simulations show that our scheme can suppress leakage to unwanted levels and reduce the error of SFQ-based Clifford gates by more than an order of magnitude.