Controlled-Not Quantum Logic Gate in Two Strongly Coupled Semiconductor Charge Qubits

TL;DR

This paper demonstrates a high-speed, high-fidelity controlled-NOT gate in strongly coupled semiconductor charge qubits, highlighting their potential for scalable quantum computing despite previous limitations.

Contribution

It presents the first benchmarking of a CNOT gate in capacitively coupled charge qubits with strong inter-qubit coupling and GHz operation speed.

Findings

Gate operations achieved at up to 5 GHz.

Fidelities comparable to spin-based two-qubit gates.

Potential for scalable quantum computing with charge qubits.

Abstract

A crucial requirement for scalable quantum-information processing is the realization of multiple-qubit quantum gates. Universal multiple-qubit gates can be implemented by a set of universal single qubit gates and any one kind of two-qubit gate, such as a controlled-NOT (CNOT) gate. Semiconductor quantum dot qubits are a leading approach for the physical implementation of quantum computation, due to their potential for large-scale integration. Two-qubit gate operations have been so far only demonstrated in individual electron spin-based quantum dot systems. Due to the relatively short de-coherence time, charge qubits in quantum dots are generally considered to be inferior for going beyond single qubit level. Here, we demonstrate the benchmarking CNOT gate in two capacitively coupled charge qubits, each consisting of an electron confined in a GaAs/AlGaAs double quantum dot. Owing to the strong inter-qubit coupling strength, gate operations with a clock speed up to 5GHz has been realized. A processing tomography shows encouragingly that the universal two-qubit gate operations have comparable fidelities to that of spin-based two-qubit gates. Our results suggest that semiconductor charge qubits have a considerable potential for scalable quantum computing and may stimulate the use of long-range Coulomb interaction for coherent quantum control in other devices.