School of Physics CM/AMO/Quantum Seminar - Dr. Aniruddha Bhattacharya

Deterministic entanglement—namely, of the kind that does not require quantum measurements—is the source of almost all advantages of quantum information systems over their classical counterparts. In this talk, I will describe some of our recent work [1] in which we theoretically show a new way of deterministically entangling two quantum-mechanical subsystems comprising photons. Our protocol entangles photons that occupy distinguishable, spatially localized modes, and works for arbitrarily large number of photons in these modes. Unlike systems of atoms, ions, molecules, or superconducting circuit elements, protocols for entangling quantum states of light are largely probabilistic, which leads to quantum information processing schemes that are inherently non-deterministic, that is, the probability of success of useful quantum operations is less than unity even in the absence of any errors. To entangle photons without uncertainties, we have utilized a deep connection between quantum mechanics and differential geometry, namely, topology. In particular, we have shown that optical waveguides can be coupled in such a way that they synthesize a mathematical structure known as holonomy, which—by utilizing the principles of conservation of total photon number and superposition of probability amplitudes—deterministically entangles photons that are incident on these waveguides.

[1] A. Bhattacharya and C. Raman, Deterministic Photonic Entanglement Arising from Non-Abelian Quantum Holonomy, Phys. Rev. Lett. 134, 080201(2025)