Reihaneh Shahrokhshahi

Ultralow-Noise Room-Temperature Quantum Memory for Polarization Qubits

Here we show an ultra-low noise regime of operation in a simple quantum memory in warm Rb atomic vapor. By modelling the quantum dynamics of four-level room temperature atoms, we achieve fidelities >90% for single-photon level polarization qubits, clearly surpassing any classical strategy exploiting the non-unitary memory efficiency. This is the first time such important threshold has been crossed with a room temperature device. Additionally we also show novel experimental techniques capable of producing fidelities close to unity. Our results demonstrate the potential of simple, resource-moderate experimental room temperature quantum devices.

Free-Space Quantum Communication with a Portable Quantum Memory

The realization of an elementary quantum network that is intrinsically secure and operates over long distances requires the interconnection of several quantum modules performing different tasks. In this work we report the interconnection of four different quantum modules: (i) a random polarization qubit generator, (ii) a free-space quantum communication channel, (iii) an ultra-low noise portable quantum memory and (iv) a qubit decoder, in a functional elementary quantum network possessing all capabilities needed for quantum information distribution protocols. We create weak coherent pulses at the single photon level encoding polarization states

Free Space Quantum Communication with Quantum Memory

|H\rangle, |V\rangle, |D\rangle, |A\rangle

Room temperature conditional

in a randomized sequence. The random qubits are sent over a free-space link and coupled into a dual rail room temperature quantum memory and after storage and retrieval are analyzed in a four detector polarization analysis akin to the requirements of the BB84 protocol. We also show ultra-low noise and fully-portable operation, paving the way towards memory assisted all-environment free space quantum cryptographic networks.

\pi

We realize a quantum communication network combining the quantum part of the BB84 protocol with room-temperature quantum memory operation. We obtain quantum bit error rates above the classical threshold for a single-photon level operation.