Microwave-assisted single photon quantum memory (MASQ)

Objective

With the unique ability to store and retrieve quantum states of photons, Quantum memories (QM) play a pivotal role in quantum information, computation and establishment of large-scale quantum communication networks (QCN). Due to the decoherence brought on by atomic collisions, current hot-vapour QMs only provides millisecond coherence times and is inefficient for building a large QCN. A unique alkali-atom-based optical QM, the 'microwave-assisted single photon quantum memory (MASQ)', which maintains the photon's state for around a second, is proposed to address this. The innovative approach combines the coherent magnetic dipole transition and spin-exchange relaxation-free (SERF) technique in a particular Zeeman manifold of Caesium atoms, which provides immunity to the decoherence caused by the dominant pair-wise spin-exchange collisional process. Another noteworthy feature of the proposed QM is its ability to store single and entangled photons. The first objective is to build a high-quality-factor 9.19 GHz cavity to create the magnetic dipole transition in the spin states of Cs, followed by constructing an all-optical Λ-QM for storing single and entangled photons. Finally, by employing cavity-mediated coherent drive, the atoms from the Λ-configuration will be shelved to the decoherence-free Zeeman states, where SERF techniques will be implemented. The scientific innovation will take place under the guidance of Prof. Oliver Benson at Humboldt Universität zu Berlin and in a secondment under Prof. Janik Wolters at the start-up AQLS, Berlin. The room-temperature memory is scalable and integrable and supports the European Quantum Communication Infrastructure's goal of creating a secure QC network across Europe.