Two-axis control of a singlet–triplet qubit with an integrated micromagnet

Qubits, the quantum-mechanical analog of classical bits, are the fundamental building blocks of quantum computers, which have the potential to solve some problems that are intractable using classical computation. This paper reports the fabrication and operation of a qubit in a double-quantum dot in a silicon/silicon–germanium (Si/SiGe) heterostructure in which the qubit states are singlet and triplet states of two electrons. The significant advance over previous work is that a proximal micromagnet is used to create a large local magnetic field difference between the two sides of the quantum dot, which increases the manipulability significantly without introducing measurable noise.