14 May 2012 Solid State Quantum Storage for Polarization Qubits

Crystal quantum memory for polarization qubits.

Physics highlights the first demonstration of a crystal quantum memory for polarization qubits by the group led by Hugues de Riedmatten. ICFO researchers show that a crystal can act as a quantum memory for photonic polarization qubits, with more than 95% fidelity on storage and retrieval processes –- beyond the maximal fidelity achievable by a classical memory. The study has been published in Physical Review Letters and highlighted in Physics. The research team includes ICFO PhD student Mustafa Gündoğan, ICFO postdoctoral researchers Drs. Patrick Ledingham and Matteo Cristiani and former ICFOnian Attaallah Almasi, now at Amsterdam University. The group is led by ICREA Prof.Hugues de Riedmatten, leader at ICFO of the Quantum photonics with solids and atoms group.

Rare-earth doped crystals are promising materials for quantum memory applications. Unfortunately, these materials have an absorption that is dependent on the polarization of the light, which means that to date, only one polarization state could be stored in these crystals. This is a strong limitation taking into account that quantum bits are often encoded in the polarization of photons. The authors overcome this limitation by coherently storing the two polarization components of a weak coherent light field at the single photon level in two different spatial modes of a Praseodymium doped crystal.