A controlled-NOT gate in a chain of qubits embedded in a spin field-effect transistor and its process tomography

TL;DR

This paper demonstrates the implementation and characterization of a CNOT gate in a chain of quantum dot qubits within a spin FET, analyzing fidelity under realistic imperfections.

Contribution

It shows the feasibility of performing CNOT gates via spin exchange interactions and local rotations in quantum dots, with process tomography and fidelity analysis.

Findings

CNOT operation is achievable within qubit coherence time.

Process fidelity decreases by at most 5% due to operation time fluctuations.

Fidelity values of 0.49 and 0.72 are obtained for different channel polarizations.

Abstract

We have investigated the realizability of the controlled-NOT (CNOT) gate and characterized the gate operation by quantum process tomography for a chain of qubits, realized by electrons confined in self-assembled quantum dots embedded in the spin field-effect transistor. We have shown that the CNOT gate operation and its process tomography are performable by using the spin exchange interaction and several local qubit rotations within the coherence time of qubits. Moreover it is shown that when the fluctuation of operation time and the imperfection of polarization of channel electrons are considered as sources of decay of fidelity, the process fidelity of CNOT decreases at most 5% by the fluctuation of the operation time and its values of 0.49 and 0.72 are obtained for polarizations of the channel spin 0.6 and 0.8, respectively.