Raman Research Institute, Bangalore, India
Symposium: “Quantum Technology” organized by Urbasi Sinha and Vibhor Singh
Photonic quantum science and technologies
The Quantum Information and Computing lab at the Raman Research Institute in Bangalore, India has been performing cutting edge research in quantum information processing towards quantum computation, quantum communication as well as fundamental tests of quantum mechanics itself using single and entangled photons. In this talk, I will present some of our recent results in the domain of experimental quantum information processing as well as quantum communications. In the first part of the talk, I will discuss a novel means of quantum state estimation that we have recently developed and experimentally demonstrated. While Quantum State Tomography has been the traditional method for characterization of an unknown quantum state, we present an interferometric method, in which any qubit state, whether mixed or pure, can be inferred from the visibility, phase shift, and average intensity of an interference pattern using a single-shot measurement—hence, we call it quantum state interferography . We then go on to show that QSI is more resource efficient than QST for quantification of entanglement in pure bipartite qubits. An extension of the scheme to pure states involving $d−1$ interferograms for d-dimensional systems (qudits) is also presented. Thus, the scaling gain is even more dramatic in the qudit scenario for our method, where, in contrast, standard QST, without any assumptions, scales roughly as $d^2$. In the second part of the talk, I will discuss our recent free space quantum key distribution experiment in the domain of secure quantum communications, which is a part of our ongoing satellite QKD project “Quantum Experiments with Satellite Technology”.  S.N.Sahoo, S.Chakraborti, A.K.Pati, US, Phys. Rev. Lett. 125 123601, 2020  Rishab Chatterjee, Kaushik Joarder, Sourav Chatterjee, Barry. C. Sanders, US, Physical Review Applied 14 024036, 2020.