New PRL publication

Probing single charge fluctuations in a semiconductor with laser spectroscopy on a quantum dot

We probe local charge fluctuations in a semiconductor via laser spectroscopy on a nearby self-assembled quantum dot. We demonstrate that the quantum dot is sensitive to changes in the local environment at the single charge level. By controlling the charge state of localized defects, we are able to infer the distance of the defects from the quantum dot with +-5 nm resolution. The results identify and quantify the main source of charge noise in the commonly-used optical field-effect devices. Based on this understanding we achieve routinely close-to transform-limited quantum dot optical linewidths.

Read the full manuscript here.


New publication in Applied Physics Letters

We have a new publication on the characterization of p-doped devices with embedded quantum dots.  We have used resonant laser spectroscopy, which is an ultra-sensitive technique to probe the mesoscopic environment of a nanostructure, to investigate the suitability of positively charged excitons in different devices for applications in quantum information science. In particular, we uncover that a sample with Be-doping is less than ideal due to dopant segregation whereas a C-doped device is ideal for applications requiring quantum coherence.

Read the full publication and a recent News & Views article in Nature Photonics by A. Tartakovski which discusses this work in the context of the recent results from NRL on hole spin dephasing in a quantum dot molecule.


New post-doc joins the group

Dr. Yong Ma joins the group.

Dr. Yong Ma comes to Edinburgh from the University of Glasgow where he worked on metamaterials and terahertz spectroscopy. He will be working on quantum dots coupled to broadband optical antennas.


3 new group members arrive

Three new group members have arrived.

Dr. Luca Sapienza joins the group as a post-doc. Luca comes to Edinburgh from NIST at Gaithersburg where he was a visiting researcher. 

Mr. Anthony Zupnik and Mr. Ted Santana have joined the group as a PhD students. Anthony recently obtained an MPhys from the University of Leeds. Ted recently completed an MSc in Physics at the Universidade Federal de Uberlândia in Brazilus.


New publication on controlling nuclear spins in a quantum dot


We present a technique for manipulating the nuclear spins and the emission polarization from a single optically active quantum dot. When the quantum dot is tunnel coupled to a Fermi sea, we have discovered a natural cycle in which an electron spin is repeatedly created with resonant optical excitation. The spontaneous emission polarization and the nuclear spin polarization exhibit a bistability. For a σ+ pump, the emission switches from σ+ to σ- at a particular detuning of the laser. Simultaneously, the nuclear spin polarization switches from positive to negative. Away from the bistability, the nuclear spin polarization can be changed continuously from negative to positive, allowing precise control via the laser wavelength. Read more here.

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