From a wide perspective, our research is mainly in the area of quantum information theory, a field jointly formed and contributed by physics, mathematics, and computer science. The goal of the field is to investigate limits on how information can be transmitted and processed when they are encoded in quantum systems. This often arises to new ways of computation or communication that manipulate quantum effects like entanglement, often providing advantages when compared to current methods. Given the generic nature of the field, quantum information theory can often be used as a toolkit to study other interesting problems, such as thermodynamics, holography and even black holes!
Thermodynamics is one of the main pillars of theoretical physics, and it has a special appeal of having wide applicability to a large variety of different physical systems. However, many assumptions in thermodynamics apply only to systems which are bulk material, i.e. consisting a large number of microscopic classical particles. Due to the advancement of designing nanoscale engines, especially in the light of devices that are used today in the processing of quantum information, is thermodynamics still applicable? Can we refine the core principles of thermodynamics to suit such nanoscale quantum systems as well?
Quantifying resources, from thermodynamics to entanglement and beyond!
I worked on developing a theory of thermodynamics that is suitable for nanoscale quantum systems, even those as small and simple as a single qubit. One of my favourite approaches is the resource theoretic framework inspired by quantum information theory. With this framework that naturally adopts the first law as an energy preserving condition, we can show the refinement of both the zeroeth and second law of thermodynamics. Most notably, the second law sees refinement in the quantum nanoregime: a family of generalized free energies arise as necessary conditions for a transition to occur. One can then utilize these laws in order to study heat engine efficiencies in the quantum regime!
One of the main lines of interest currently is about the phenomenon of catalysis in quantum thermodynamics -- the fact that using an ancillary system provides us a means to bypass certain restrictions on thermodynamic state preparation! Furthermore, as we study this effect, we realized that the degree to which our catalyst degrades in the process leads to qualitatively different behaviours on the systems of interest. Catalysis not only exists in thermodynamics, but also entanglement theory and the manipulation of various quantum resources -- giving us a theoretical handle to study many different questions!
Thermodynamics in many-body systems
Having delved deep into the resource-theoretic approach to quantum thermodynamics, my curiosity naturally extended to exploring its connections with other frameworks like fluctuation theorems and master equations. In the course of my postdoctoral endeavors, I ventured into the application of quantum thermodynamics to the realm of many-body physics. This journey involved delving into topics such as many-body localization and the cooling of Bose-Einstein Condensate (BEC) quasi-condensates in the challenging nanoKelvin temperature range. My fascination with these subjects just continues to grow :)
Collaborating with our experimental partners, we embarked on a fascinating exploration of quantum gases as a compelling platform for witnessing thermodynamic operations. Our collective pursuit involves unraveling the intricate physics of cold gases and devising innovative methods to control and observe them. Together, we're pushing the boundaries of understanding and manipulating quantum systems, driving the forefront of research into new and exciting territories.
Quantum Information and Cryptography
Quantum information science has offered a new set of perspectives on computing, by invoking fundamental laws of quantum physics to develop more sophisticated algorithms for problem solving. However, these new discoveries pose a threat to the security of a large class of currently existing cryptographic protocols, which rely crucially on the conjectured computational complexity of certain mathematical problems. Therefore, these challenges require us to revise current methods of cryptography. Fortunately, what threatens us also potentially liberates us: by making use of quantum methods to transmit and process information, one can devise new protocols that achieve higher levels of security, without relying on computational assumptions. The best known example is quantum key distribution (QKD), where two honest parties work together to generate a secure key which stays shielded from any potential eavesdropper.
Apart from QKD, a large class of different protocols called two-party cryptographic protocols have also been studied. These are protocols that do not involve a third eavesdropper, however, they consist of two distinct players who are unwilling to trust each other, but nevertheless want to jointly perform a task. I study the performance of such two party quantum protocols (such as bit commitment and oblivious transfer) under physical assumptions where each party has a limited amount/quality of quantum storage.
During my PhD years I've had the pleasure to work with Stephanie Wehner and Thomas Vidick to produce lecture notes for their MOOC class on quantum cryptography. Check out the course on Edx!
The entropic framework is one of the most versatile tools I've learnt in my dabbling with cryptography: not only is the mathematical structure fascinating, but due to their operational significance in generic information processing tasks, they can be widely applicable in many other aspects (such as thermodynamics!).
The meaning of in.Q
in.Q officially stands for information & quantum.
It also stands for the spirit of scientific "inquiry", which is the curious wonder as we go about understanding the world.
Group members are called the inQlings, reminiscent of a literary group that gave us writers like Tolkien and Lewis.