Past Events

The Department of Physics and the HKU-UCAS Joint Institute of Theoretical and Computational Physics have launched a colloquium series jointly. The detailed schedule and talk information are as below.

Quantum Chaos and Physical Distance Between Quantum States

Speaker: Prof. Biao WU
Affiliation: Peking University
Date: August 24, 2022 (Wednesday)
Time: 5:00 p.m.
Zoom Link: https://bit.ly/3dALWg1
Meeting ID: 966 3677 3066
Password: 2859
Poster: Download
Abstract:
It has been long argued and accepted that there is no true quantum chaos due to the linearity of the Schrödinger equation. Berry even suggested to change quantum chaos, a confusing oxymoron, to quantum chaology as the study of quantum systems whose classical counterparts exhibit chaos. We show that there is genuine quantum chaos despite that quantum dynamics is linear. This is revealed by introducing a physical distance between two quantum states. Qualitatively different from existing distances for quantum states, for example, the Fubini-Study distance, the physical distance between two mutually orthogonal quantum states can be very small. As a result, two quantum states, which are initially very close by physical distance, can diverge from each other during the ensuing quantum dynamical evolution. This kind of sensitivity to initial conditions is reduced to the one in classical dynamics in the semiclassical limit. In the end, we discuss how nonlinear Newton’s equations of motion emerge out of the linear Schrödinger equation.

Quantum Entangled Interferometers and Their Applications

Speaker: Prof. Zheyu Jeff OU
Affiliation: City University of Hong Kong 
Date: August 31, 2022 (Wednesday)
Time: 3:00 p.m.
Hybrid Mode
In Person: Room 522, 5/F, Chong Yuet Ming Physics Building, HKU
Zoom Link: https://bit.ly/3AaGdoC
Meeting ID: 912 3549 7373
Password: 2859
Poster: Download
Abstract:
A new type of quantum interferometer utilizes nonlinear parametric processes as the wave splitting and recombination elements. Because of the nonlinear interaction, the fields inside the interferometer are intrinsically entangled and quantum mechanically correlated. This type of quantum correlated interferometer exhibits some unique properties that we will review in this talk. Because of these properties, this type of interferometer is superior to traditional beam splitter-based interferometers in many aspects. We will present its various forms and its realizations with different types of waves such as microwave, atomic waves (both internal and external degrees), and sound waves. We will discuss its applications in quantum metrology, quantum imaging, quantum spectroscopy, and quantum state engineering.