Research

If a quantum system is hard to be characterized, let us treat it as a black box!

Quantum theory predicts many fascinating phenomena that are impossible to observe in classical physics. Some of these quantum phenomena are necessary to perform certain quantum technologies. For instance, quantum entanglement is a necessary property to distribute secure keys in a communication scheme or to realize quantum algorithms in a quantum computer. Other important phenomena include steering, nonlocality, incompatible measurements, coherence, nonmacrorealism, etc. We are interested in characterizing, verifying, and quantifying these quantum phenomena. To make our protocols applicable to quantum technologies requiring a high level of security (e.g., quantum communication and quantum computation), our protocols are often embedded in a "black-box" (device-independent) framework.

Our research methods involve analytical and numerical approaches, depending on the preferences of group members. Many of our theoretical results can be demonstrated experimentally (see some of the following experimental results demonstrated by other groups).

Quantum Steering

Quantum steering is a phenomenon that allows an observer to remotely steer and prepare the other observer's quantum states. It is a useful tool for entanglement detection when the information about some devices involved cannot be fully accessed. See, Refs. [1a] [1b] [1c] [1d]for some of our results and Ref. [1e] for collaboration with an experimental group.

Measurement Incompatibility

In quantum theory, due to the Heisenberg uncertainty principle, some of the measurements cannot be simultaneously performed, called incompatible measurements. They are necessary to implement quantum communication. Studying incompatibility is also a central topic in the foundation of quantum theory. See. Refs. [2a] [2b] [2c] for some of our results.

Quantum System Identification

In an extreme case, the data collected from a black-box scenario can directly identify the detailed description of the system. Such a case is called "self-testing". See Refs. [3a] [3b] for our recent works. Results of [3b] was also put on GitHub.

Quantum Temporal Correlations

Studying quantum temporal correlations allows us to understand the dynamics of a quantum system, the properties of a quantum channel, and the interaction between systems and environments. See. Refs. [4a] [4b] [4c] for some of our previous results and Ref. [4d] for experimental demonstration by other groups.