UNC Physics Colloquium

Yinyu Liu, Harvard University

Quantum information processing based on spins in semiconductor quantum dots

Abstract
The field of Quantum Information is of great excitement in both fundamental physics and industry. One promising platform for quantum computing is gate-defined quantum dots in semiconductors. The greatest limiting factor currently is that delicate quantum states can lose their quantum nature due to interactions with their environment. Other open challenges are to coherently control large-scale spin qubits and develop methods to entangle quantum bits that are separated by significant distances.
Silicon-based materials are promising due to the long lifetimes of electrons’ quantum states, but also challenging due to the difficulty in fabrication and valley degeneracy. I will report a singlet-triplet qubit with a qubit gate that is assisted by the valley states. This work would potentially relax the design and fabrication requirement for scaling. Moreover, strong coupling between electron spins and photons in hybrid circuit-QED architecture has been achieved in this research field. Quantum optics, long-distance quantum entanglement, and communication via photons are promised. To address that, I will present my project on indium arsenate (InAs) double quantum dots (DQD) that are embedded in circuit-QED architecture. We demonstrated the direct evidence of photon emission from a DQD in the microwave regime. By achieving stimulated emission from one DQD in these works, we invented a semiconductor single atom maser that can be tuned in situ. I will demonstrate that a semiconductor-based quantum dot is a promising platform for quantum information as well as for fundamental physics.