Pascale looks at the exotic things that happen when photons interact in special semiconductor nanostructures that her team and she create in the lab. Host: Martin van Exter
Semiconductor quantum dots (QDs) are promising artificial atoms for quantum information processing: they can generate flying quantum bits in the form of single photons; they show single photon sensitivity that can be used to develop quantum logic gates and the spin of a carrier trapped in a QD can be used as a quantum memory. The scalability of a QD based quantum network requires efficient interfaces between stationary and flying quantum bits. In the last few years, our group has made important progresses in this direction using cavity quantum electrodynamics.
With a deterministic positioning of a single QD in a microcavity, we control the QD spontaneous emission on demand, either in the weak or strong coupling regime [1]. With such a tool, we fabricate highly efficient single photon sources: each single photon emitted by the QD is collected with 80% probability [2]. By minimizing the charge noise around the QD in a gated structure [3], we demonstrate the generation of fully indistinguishable photons, with very high single photon purity. The brightness of the source is shown to exceed by two orders of magnitude the one of a parametric down-conversion source with similar properties [4]. Symmetrically, we have made important progresses in the development of an efficient interface between a flying quantum bit and a stationary one. A single spin in a cavity is shown to rotate the polarization of photons by few degrees depending on the spin state [5]. Most recently, we have reached the regime where coherent control of a quantum bit can be done when only few photons are sent on the device.
The van der Waals colloquium takes place at 16:00 sharp in the Sitterzaal, and is followed by a borrel (Beer! Snacks! Physics!). Each colloquium starts with an opening act by a local student (10min) before the main talk (45+10min). Unless otherwise noted, a special coffee hour for PhD students takes place on the morning of the colloquium, 11.30 – 12.30h in the C.J.Gorterzaal (1st floor Oortbuilding). If you would like to talk to the guest, please contact Yvonne (Kerkhof@Physics.LeidenUniv.nl) or the host.