JWST: An Observatory Beyond the Moon


The Quantum Loom: efficient generation of photonic graph states

Hagai Eisenberg

Racah Institute of Physics, Hebrew University of Jerusalem, Israel

The generation of entanglement between more than two particles is a major challenge for all physical realizations. It is required for the realization of many quantum information protocols, including quantum computing. Single photons are one of the most promising realizations of quantum bits (qubits), as they are easily manipulated, preserve their coherence for long times, and information can be stored in their many different degrees of freedom. Up to date, up to ten photons have been entangled in a single state through their polarization degree of freedom. The main difficulties in increasing this number are the elaborated setups required and the low rates of state production.

I will present a novel and simple scheme that can in principle generate entanglement between any number of photons in a linear cluster state from a single fixed setup. This scheme combines photons from one source in a single path, but at different times, using an optical delay. It can be extended to create higher-dimensional cluster states, and even arbitrary graph states. Such states are useful for the one-way quantum computer scheme. Results from such a setup using heralded single photons will be presented. States of two and three entangled photons were measured, with good visibilities of their quantum interference.

“A resource efficient source of multi-photon polarization entanglement”, E. Megidish, T. Shacham, A. Halevy, L. Dovrat and H.S. Eisenberg, Phys. Rev. Lett. 109, 080504 (2012).

“Entanglement swapping between photons that have never coexisted”, E. Megidish, A. Halevy, T. Shacham, T. Dvir, L. Dovrat, and H. S. Eisenberg, Phys. Rev. Lett. 110, 210403 (2013).

“Simple source for large linear cluster photonic states”, Y. Pilnyak, N. Aharon, D. Istrati, E. Megidish, A. Retzker, H. S. Eisenberg, Phys. Rev. A 95, 022304 (2017)