Micromachined integrated quantum circuit containing a superconducting qubit

TL;DR

This paper reports the development of a multilayer microwave integrated quantum circuit with a superconducting qubit and micromachined cavity, demonstrating strong coupling and coherence suitable for quantum computing.

Contribution

It introduces a novel fabrication of a multilayer integrated quantum circuit with high-quality superconducting components and demonstrates strong qubit-cavity coupling in a micromachined architecture.

Findings

Superconducting cavity lifetime of 34.3 microseconds with a quality factor of 2 million.

Qubit coherence times of 6.4 microseconds (T1) and 11.7 microseconds (T2 Echo).

Strong dispersive qubit-cavity coupling with rate -1.17 MHz.

Abstract

We present a device demonstrating a lithographically patterned transmon integrated with a micromachined cavity resonator. Our two-cavity, one-qubit device is a multilayer microwave integrated quantum circuit (MMIQC), comprising a basic unit capable of performing circuit-QED (cQED) operations. We describe the qubit-cavity coupling mechanism of a specialized geometry using an electric field picture and a circuit model, and finally obtain specific system parameters using simulations. Fabrication of the MMIQC includes lithography, etching, and metallic bonding of silicon wafers. Superconducting wafer bonding is a critical capability that is demonstrated by a micromachined storage cavity lifetime $34.3~\mathrm{\mu s}$, corresponding to a quality factor of 2 million at single-photon energies. The transmon coherence times are $T_1=6.4~\mathrm{\mu s}$, and $T_2^{Echo}= 11.7~\mathrm{\mu s}$. We measure qubit-cavity dispersive coupling with rate $\chi_{q\mu}/2\pi=-1.17~$MHz, constituting a Jaynes-Cummings system with an interaction strength $g/2\pi=49~$MHz. With these parameters we are able to demonstrate cQED operations in the strong dispersive regime with ease. Finally, we highlight several improvements and anticipated extensions of the technology to complex MMIQCs.