Cryptography  Information Theory  Foundations 

Quantum Cryptography

Quantum communication offers significant advantages when it comes to achieving cryptographic security. The classical example is quantum key distribution which allows two distant parties to establish a secure key. However, quantum communication can also help us to solve many other cryptographic problems. One of the things that we are interested in is the question of what resources allow us to solve cryptographic tasks between two parties who do not trust each other such as bit commitment, oblivious transfer or secure identifcation. For example, we introduced and work on the so-called noisy-storage model. Recent work examines the power of relativity for cryptography. A question that we are particularly excited about right now is whether we can develop a very general resource theory for quantum cryptography which tells us what kind of output states can be obtained from particular input states in the presence of cheating parties.

Quantum Information Theory

Quantum information differs signficantly from classical information and the presence of entanglement has often thwarted our classical intuition. Our goal is to determine and understand the extend of this difference. On the one hand, we are interested in understanding communication aspects of quantum information, that is, quantum information theory. For example, we would like to understand limits to a quantum channels ability to transmit information, i.e., its capacity. To this end, we have tried to tackle the problem from the opposite end and derived several strong converses for channel coding which determine sharp limits on our ability to send any information.
On the other hand, we are interested in what our newfound knowledge of how information behaves in small systems can tell us about physics itself. One thing that we are presently quite excited about is to investigate what quantum information theory can tell us about the foundations of statistical mechanics.


Quantum mechanics is often counterintuitive, but has proven highly effective in predicting the outcome of physical experiments. Yet, we still have a very limited understanding of its foundations. As we are after all interested in understanding nature, one may sometimes wonder what the mathematical rules of quantum mechanics really imply about nature and why they cannot (maybe) be any different. One of our goals is thus to understand the physical implications and significance of the mathematical formalism. To this end, we often like to take a step back and examine much more general classes of physical theories in order to understand what makes quantum mechanics so special. For example, we recently examined a possible physical motivation why the uncertainty principle should not be violated. In the past, we have also linked concepts such as uncertainty and non-locality. One of the things that we are quite excited about right now is to explore the relations between measurements that are very uncertain, and their ability to create randomness from a largely unknown quantum state.


Centre for Quantum Technologies

We are located at the Centre for Quantum Technologies, at the National University of Singapore, Block S15, Level 4.