Welcome!

I’m currently a graduate student in the Quantum Science and Technologies Group in the Hearne Institute for Theoretical Physics at Louisiana State University under the supervision of Mark Wilde.  Previously, I was a Master’s student at the Institute for Quantum Computing at the University of Waterloo under the supervision of Norbert Lütkenhaus.

My research is in the general area of quantum information theory. For the past couple of years my focus has been on quantum cryptography, specifically quantum key distribution. I am also interested in quantum networks as well as quantum computing, specifically applying machine learning methods to quantum algorithms for near-term applications. Check out my research for details on what I’ve been working on, as well as my Google Scholar page and my papers on arXiv. I’ve also compiled a list of introductory resources on the topics pertaining to my research and to physics in general.

You can contact me at skhatr5 [at] lsu [dot] edu.

Latest Papers

Quantum-assisted quantum compiling

Abstract:

Compiling quantum algorithms for near-term quantum computers (accounting for connectivity and native gate alphabets) is a major challenge that has received significant attention both by industry and academia. Avoiding the exponential overhead of classical simulation of quantum dynamics will allow compilation of larger algorithms, and a strategy for this is to evaluate an algorithm’s cost on a quantum computer. To this end, we propose quantum-assisted quantum compiling (QAQC). In QAQC, we use the Hilbert-Schmidt inner product between a target unitary U and a trainable unitary V as the cost function to be evaluated on the quantum computer. We introduce two circuits for evaluating this cost. One circuit computes |Tr(VU)|, and we use this circuit for gradient-free compiling. Our other circuit gives Tr(VU) and is a generalization of the Power of One Qubit that we call the Power of Two Qubits. We use this circuit for gradient-based compiling. As a demonstration of QAQC, we compile various one-qubit gates on IBM’s and Rigetti’s quantum computers into their respective native gate alphabets. Future applications of QAQC include algorithm depth compression, black-box compiling, noise mitigation, and benchmarking.

Robust quantum network architectures and topologies for entanglement distribution

Abstract:

Entanglement distribution is a prerequisite for several important quantum information processing and computing tasks, such as quantum teleportation, quantum key distribution, and distributed quantum computing. In this work, we focus on two-dimensional quantum networks based on optical quantum technologies using dual-rail photonic qubits. We lay out a quantum network architecture for entanglement distribution between distant parties, with the technological constraint that quantum repeaters equipped with quantum memories are not currently widely available. We also discuss several quantum network topologies for the building of a fail-safe quantum internet. We use percolation theory to provide figures of merit on the loss parameter of the optical medium for networks with bow-tie lattice and Archimedean lattice topologies. These figures of merit allow for comparisons of the robustness of different networks against intermittent failures of its nodes and against intermittent photon loss, which is an important consideration in the realization of the quantum internet.

Fundamental limits on quantum dynamics based on entropy change

Abstract:

It is well known in the realm of quantum mechanics and information theory that the entropy is non-decreasing for the class of unital physical processes. However, in general, the entropy does not exhibit monotonic behavior. This has restricted the use of entropy change in characterizing evolution processes. Recently, a lower bound on the entropy change was provided in [Buscemi, Das, & Wilde, Phys. Rev. A 93(6), 062314 (2016)]. We explore the limit that this bound places on the physical evolution of a quantum system and discuss how these limits can be used as witnesses to characterize quantum dynamics. In particular, we derive a lower limit on the rate of entropy change for memoryless quantum dynamics, and we argue that it provides a witness of non-unitality. This limit on the rate of entropy change leads to definitions of several witnesses for testing memory effects in quantum dynamics. Furthermore, from the aforementioned lower bound on entropy change, we obtain a measure of non-unitarity for unital evolutions.