Controlled-Z gate for transmon qubits coupled by semiconductor junctions

TL;DR

This paper proposes a method to implement a high-fidelity controlled-Z gate for transmon and gatemon qubits coupled via semiconductor junctions, with electrical control enabling fast quantum operations.

Contribution

It introduces three configurations of semiconductor junction-coupled qubits and demonstrates their potential for fast, low-error controlled-Z gate implementation.

Findings

CZ gate can be performed under 50 ns

Gate error can be below 10^{-4}

Electrical control via gate voltage enables tunable coupling

Abstract

We analyze the coupling of two qubits via an epitaxial semiconducting junction. In particular, we consider three configurations that include pairs of transmons or gatemons as well as gatemon-like two qubits formed by an epitaxial four-terminal junction. These three configurations provide an electrical control of the interaction between the qubits by applying voltage to a metallic gate near the semiconductor junction and can be utilized to naturally realize a controlled-Z gate (CZ). We calculate the fidelity and timing for such CZ gate. We demonstrate that in the absence of decoherence, the CZ gate can be performed under $50\ {\rm ns}$ with gate error below $10^{-4}$.