Flux-tunable heat sink for quantum electric circuits

M Partanen,J Tuorila,K Y Tan,M Jenei,T Ala-Nissila,J Govenius,L Grönberg,R E Lake,V Vesterinen,S Simbierowicz,M Möttönen,S Masuda,J Hassel

doi:10.1038/s41598-018-24449-1

Abstract

Superconducting microwave circuits show great potential for practical quantum technological applications such as quantum information processing. However, fast and on-demand initialization of the quantum degrees of freedom in these devices remains a challenge. Here, we experimentally implement a tunable heat sink that is potentially suitable for the initialization of superconducting qubits. Our device consists of two coupled resonators. The first resonator has a high quality factor and a fixed frequency whereas the second resonator is designed to have a low quality factor and a tunable resonance frequency. We engineer the low quality factor using an on-chip resistor and the frequency tunability using a superconducting quantum interference device. When the two resonators are in resonance, the photons in the high-quality resonator can be efficiently dissipated. We show that the corresponding loaded quality factor can be tuned from above 105 down to a few thousand at 10 GHz in good quantitative agreement with our theoretical model.

Highlights

One of the most promising approaches to building a quantum computer is based on superconducting qubits in the framework of circuit quantum electrodynamics[1,2,3,4,5,6]
The modes of Resonator 2 are tunable owing to a superconducting quantum interference device (SQUID), acting as a flux-tunable inductance, placed in the middle of the resonator
The SQUID is integrated into the center pin of the waveguide and consists of two aluminium layers separated by an insulating aluminium oxide layer

Summary

Introduction

One of the most promising approaches to building a quantum computer is based on superconducting qubits in the framework of circuit quantum electrodynamics[1,2,3,4,5,6]. Many quantum error correction codes require frequent initialization of ancillary qubits during the computation. In this work we focus on a specialized initialization circuit, which remains to be implemented in superconducting quantum processors. A promising qubit initialization protocol based on dissipative environments was proposed in refs[15,16]. We experimentally realize such a tunable dissipative environment and study its effect on a superconducting resonator. Tunable transmission lines are useful in studying fundamental quantum phenomena[26,27]. Dissipation is in some cases beneficial for quantum computing[28], lossy materials are typically harmful for qubit lifetimes during computation. We tune the Q factor from above 105 down to a few thousand by coupling the resonator relatively strongly to a dissipative element. The integrated resistive element we introduce does not inherently degrade the Q factor when it is weakly coupled to the resonator compared to fabricated resonators without any engineered resistive elements

Methods

Results

Conclusion