Progress toward a capacitively mediated CNOT between two charge qubits in Si/SiGe

E R Macquarrie,Brandur Thorgrimsson,M A Eriksson,Nathan Holman,Samuel F Neyens,M Palma,J P Dodson,Mark Friesen,J Corrigan,S N Coppersmith,L F Edge

doi:10.1038/s41534-020-00314-w

E R Macquarrie, Brandur Thorgrimsson + Show 9 more

Open Access

https://doi.org/10.1038/s41534-020-00314-w

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Abstract

Fast operations, an easily tunable Hamiltonian, and a straightforward two-qubit interaction make charge qubits a useful tool for benchmarking device performance and exploring two-qubit dynamics. Here, we tune a linear chain of four Si/SiGe quantum dots to host two double dot charge qubits. Using the capacitance between the double dots to mediate a strong two-qubit interaction, we simultaneously drive coherent transitions to generate correlations between the qubits. We then sequentially pulse the qubits to drive one qubit conditionally on the state of the other. We find that a conditional π-rotation can be driven in just 74 ps with a modest fidelity demonstrating the possibility of two-qubit operations with a 13.5 GHz clockspeed.

Highlights

With charge, valley, and spin degrees of freedom, quantum dots in silicon are promising hosts of many different types of qubits
Two-qubit gates in Si quantum dots have been mediated by a spin–spin exchange interaction or by coupling via a superconducting resonator[10]
Encoded qubits that have a tunable electric dipole moment such as the quantum dot hybrid qubit (QDHQ) stand to benefit from this fast gate speed without suffering from dephasing during idle periods

Summary

Introduction

Valley, and spin degrees of freedom, quantum dots in silicon are promising hosts of many different types of qubits. A capacitive interaction can be used to coherently couple neighboring double dot qubits using the electronic charge degree of freedom. In Si-based quantum dot devices, a strong[14] and tunable[15] capacitive interaction between double dots has been demonstrated and used to perform qubit control conditionally on the state of a classical two level system[16]. The strength of this interaction makes it a promising candidate for coupling qubits that have a tunable charge dipole moment such as the quantum dot hybrid qubit (QDHQ)[17–19]. We use capacitively-coupled charge qubits to explore these challenges by measuring correlated oscillations between two simultaneously-driven qubits, by using those dynamics to synchronize our multi-qubit control channels, and by using this interaction to drive a fast (74 ps) conditional π-rotation

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Results

Conclusion