In situ Qubit Frequency Tuning Circuit for Scalable Superconducting Quantum Computing: Scheme and Experiment

TL;DR

This paper introduces a scalable in situ superconducting circuit using rf-SQUIDs for qubit frequency tuning, addressing heating and cabling issues in large-scale quantum processors through a time-division-multiplex scheme.

Contribution

Proposes a novel in situ qubit frequency tuning scheme with experimental validation, significantly reducing cabling and heating problems for scalable superconducting quantum computing.

Findings

The scheme effectively modulates qubit frequency with single pulses.

It reduces control cabling from ~3n to ~log2(3n)+1 for n qubits.

Experimental results confirm the scheme's feasibility.

Abstract

Frequency tunable qubit plays a significant role for scalable superconducting quantum processors. The state-of-the-art room-temperature electronics for tuning qubit frequency suffers from unscalable limit, such as heating problem, linear growth of control cables, etc. Here we propose a scalable scheme to tune the qubit frequency by using in situ superconducting circuit, which is based on radio frequency superconducting quantum interference device (rf-SQUID). We demonstrate both theoretically and experimentally that the qubit frequency could be modulated by inputting several single pulses into rf-SQUID. Compared with the traditional scheme, our scheme not only solves the heating problem, but also provides the potential to exponentially reduce the number of cables inside the dilute refrigerator and the room-temperature electronics resource for tuning qubit frequency, which is achieved by a time-division-multiplex (TDM) scheme combining rf-SQUID with switch arrays. With such TDM scheme, the number of cables could be reduced from the usual $\sim 3n$ to $\sim \log_2{(3n)} + 1$ for two-dimensional quantum processors comprising $n$ qubits and $\sim 2n$ couplers. Our work paves the way for large-scale control of superconducting quantum processor.