Institute of Information Science Academia Sinica
Topic: From Quantumness to Security
Speaker: Prof. Xiong-Feng Ma (Institute for Interdisciplinary Information Sciences)
Date: 2017-02-15 (Wed) 16:00 – 17:20
Location: Auditorium 106 at IIS new Building
Host: Kai-Min Chung


Coherence and entanglement are two peculiar features of quantum theory. Coherence captures the phenomenon of coherent superposition of quantum states, while entanglement, “the spooky action at a distance”, plays a crucial role in the nonlocality of quantum mechanics. In this talk, I shall present two links: between coherence and randomness in quantum random number generation, and between entanglement and security in quantum key distribution.

Random numbers play an indispensable role in modern society in various arenas of finance, cryptography, and computation. Considering individual and coherent measurement of the correlated party, we show that the coherence of formation and the relative entropy of coherence measure the quantum randomness for these two situations, respectively. Furthermore, we calculate the gap between the two quantum randomness, which turns out to related another quantum correlation --- discord.

In quantum information processing, entanglement becomes an important resource for various tasks, such as teleportation, quantum computation, and cryptography. Intuitively, entanglement means a strong nonlocal correlation between distant parties, which essentially offers a secure key generation tool. Various Bell’s inequality test experiments have proved that eavesdropping (as a local hidden variable) can be fundamentally ruled out. In this talk, I shall link the basic concept of entanglement with the security of key distribution.


Xiongfeng Ma’s main research interest lies on quantum information and quantum optics, particularly in quantum cryptography and correlation. After obtaining his BSc at Peking University in 2003, Xiongfeng attended the University of Toronto for his PhD degree. From 2008 to 2011, he did his post-doc and visiting positions at the University of Waterloo, the University of Toronto, and the University of Leeds. In 2012, Xiongfeng joined Tsinghua University as an assistant professor.