Quantum Science Forum: Semiconductor Spin-Cavity Quantum Transistors for Future Computers and Internet


Date: 7-Jan-2020 Time: 10:00am 

Venue: Conference Hall 320 
Speaker: Dr. Chengyong HU (Department of Electrical and Electronic Engineering, University of Bristol, UK)


The invention of computers and Internet has changed our daily lives so widely and deeply, and this trend is accelerating in recent years with the development of cloud computing, big data, artificial intelligence and Internet of things. However, the fundamental building  blocks, i.e., the traditional field-effect transistors(FETs) would fail in several years due to quantum effects when the device size goes down to several nanometres.  Although the current Internet is already very fast and flexible, it is neither energy efficient nor secure as it continues to use electrons for information processing and photons for information transporting, thus the energy-consuming optical-electrical/electrical-optical conversions are still indispensable. The future Internet is very likely a mixture of all-optical Internet (with high speed and low energy consumption) and quantum Internet (with absolute security) where (single) photons in replace of electrons are used for information processing. The regular Internet would be used as a default, but would switch to quantum Internet when sensitive data (e.g., a credit card number) need to be transmitted. However, the long-sought optical information processing and optical buffering technologies for all-optical networks have not been achieved yet, and the lack of quantum repeaters also hinders the development of long-distance quantum communication networks.
To resolve the above challenges, here I introduce two-types of spin-cavity quantum transistors based on the giant optical Faraday rotation(GFR) and giant optical circular birefringence(GCB) induced by a single electron spin confined in a semiconductor quantum dot in optical microcavities. These high-speed (up to THz) quantum transistors feature the duality as quantum gates for scalable quantum information processing and classical optical transistors for high-speed optical information processing. The classical transistor operation is just a specific case of a quantum transistor which is more general. I will show these quantum transistors can be used as deterministic photon-spin and photon-photon quantum gates for  generation of >1000-photon entanglement, deterministic photon-spin quantum interface, complete Bell-state analyzers, full quantum repeaters and quantum routers,  with which all-optical computers and all-optical Internet, quantum computers and quantum Internet can be constructed. Recent experimental progress has indicated that these spin-cavity quantum transistors is realizable with the state-of-the-art semiconductor technology. This semiconductor platform for quantum computers can integrate millions of such spin-cavity transistors on a cm2 chip, and represents a new route to build workable quantum computers, superior to the superconducting quantum computers pursued by Google and IBM in terms of speed, qubit density and capability for networking. In analogy to the traditional transistors that had brought a revolution in electronics and information technology (IT) in the 20th century, these quantum transistors could bring another revolution in information and communication technology (ICT) and quantum technologies in the 21st century. 

About the speaker: 

Dr. Chengyong HU received B.S. in Physics from Beijing University, M.S. in Physics from Institute of Physics (CAS) and Ph.D. in Physics from University of Wuerzburg and Institute of Semiconductors (CAS). He is a research fellow with EE Dept at the University of Bristol since 2008 and has been working on semiconductor quantum technologies, including cavity-QED enhanced quantum dot single photon sources and semiconductor spin-based quantum gates, quantum repeaters, quantum memories and quantum transistors for quantum computers and quantum networks, all-optical computers and all-optical networks. His expertise covers cavity quantum-electrodynamics (CQED), quantum optics, quantum information and semiconductor physics. He has published 44 peer-refereed journal papers with 2200 citations.