ECE Seminar: Yinyu Liu, Harvard



Contact for Zoom login info. Quantum information processing based on semiconductor quantum dots Abstract: The field of Quantum Information has recently become an area of great excitement in both fundamental physics and industry. One promising platform for quantum computing is gate defined quantum dot 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 develop methods to entangle quantum bits that are separated by significant distances and can be measured quickly with high fidelity. In my talk, I will first present my project that has positioned to address these challenges on indium arsenate (InAs) double quantum dots (DQD) that is embedded in circuit-QED architecture. We demonstrated the direct evidence of photon emission from a DQD in the microwave regime and further achieved stimulated emission in a similar system. By achieving stimulated emission from one DQD in these works, we invented a semiconductor single atom maser that can be tuned in situ. To show a better merit of the maser performance, we experimentally examined the phase stabilization of the semiconductor DQD maser via the injection locking effect. We demonstrate that the linewidth can be improved to as narrow as 1 Hz and gave a proof of principle demonstration of qubit readout. Then I will go through the progress of the SiGe spin qubit project that aimed at high fidelity spin qubit. 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 qubit gate that is assisted by the valley states. I will demonstrate that a semiconductor based quantum dot is a promising platform for quantum information as well as for fundamental physics. Bio: Yinyu Liu is a postdoctoral fellow at Harvard University and is leading a quantum information project in Professor Amir Yacoby’s group. She obtained her bachelor degree from Tsinghua University and completed her graduate work at Princeton University in the laboratory of Professor Jason Petta. Her PhD project focused on photon emission from semiconductor quantum dots integrated in a superconducting circuit quantum electrodynamics (cQED) architecture. Currently she is working on spin qubits fabricated from SiGe quantum wells, which enable longer lifetimes than other physical systems without sacrificing controllability.