Generation and Manipulation of Single Collective Excitations in Atomic Quantum Memory

Michal Parniak
June 12th, 2018 MICHAL PARNIAK Quantum Memories Lab, Faculty of Physics
University of Warsaw

In a recent experiment performed in our group we demonstrated the ability to generate on-demand single photons using a cold atom quantum memory. The photons originating from a laser-cooled atoms held in a magnetooptical trap are an ideal candidate for implementation of a quantum repeater protocol - an essential component of a quantum communications network. By introducing the multiplexing of angular emission modes we effectively create a highly multimode source of quantum light. We are able to multiplex at least 600 independent modes and store atomic excitations for over 50 μs. The memory feature enables real-time feedback, that could lead to a nearly-deterministic single-photon source.

We also certify that the system contains atom-photon multidimensional entanglement. This is witnessed by entropic methods, which we find particularly well-suited to study position-momentum entanglement. We utilize Bayesian entropy estimation techniques that reliably estimate entropy of a spatial distribution even in the undersampled regime.

Along with these ideas I will discuss our most recent maniuplation of single photons stored as spin waves in our quantum memory, which could be a way to realize simple quantum processing protocols within the linear-optical scheme. In particular, by spin-wave diffraction-based beamsplitter realized usign a periodic ac-Stark modulation we performed Hong-Ou-Mandel interference of heralded single spin waves.

Seminar, June 12, 2018, 14:00. ICFO’s Blue Lecture Room

Hosted by Prof. Morgan Mitchell