Quantum Physics Seminar: "Quantum applications: from continuous protection of a quantum memory against Doppler dephasing, through cooling of a levitated nanodiamond, to entangling quantum gates in a quantum network."

Tue, 16/04/2019 - 12:00 to 13:30

Danciger B building, Seminar room
Speaker: Itsik Cohen, AARHUS University Abstract: In this talk I will present three different projects I have been working on. 1. Protecting quantum memory against Doppler dephasing: Although inhomogeneous Doppler broadening is important for absorbing a short temporal photon in the different velocity groups of an atom gas, the same mechanism causes dephasing of the already stored photon, thus limiting the memory duration. Instead of applying the well known photon Hahn echo, we propose to weakly drive an off resonant transition to an auxiliary level, resulting in a velocity dependent AC stark shift, which continuously counters the undesired Doppler term. 2. Cooling of a levitated nanodiamond: Trapped by optical tweezers or a Paul trap, a nanodiamond can still rotate in three directions. In order to use these rotational modes for quantum applications, one should first cool them. Similarly to laser cooling of atoms using their internal degrees of freedom, we theoretically explore the combined laser and microwave cooling using the NV defect for generating a friction torque. 3. Entangling quantum gates in a quantum network: We propose a simple interaction protocol to be implemented on a scalable quantum network, in which the quantum nodes consist of qubit systems confined in cavities. The nodes are deterministically coupled by a single photon, which is disentangled from the qubits at the end of the coupling operation, while generating an entangling controlled-phase gate between the qubits in the network.