Our work concentrates on novel nanostructures for optics at the single photon and single electron level, we study different systems: semiconducting nanowires, superconducting detectors, atomic-solid state hybrid systems with the aim of combining these systems in quantum information processing experiments.
Nanowire Quantum LED
Semiconductor nanowires have strong potentials for merging quantum optics and quantum transport. We study quantum dots in nanowires that are defined by heterostructures, a thin layer of a low bandgap material such as GaInAsP in an InP nanowire can be grown using epitaxial growth techniques. Our optical studies have demonstrated high quality quantum dots with narrow emission linewidth, single photon generation and spin memory. By controlling the shape of the nanowire, very high extraction efficiencies can be reached.
Image: artistic view of a single quantum dot in a nanowire.
Based on the successful photoluminescence studies of quantum dots in nanowires, we are developing a quantum light emitting diode. This is a single electron to single photon interface, with proper selection rules, the electron to photon conversion can be made coherent. Additionally the process is reversible and a single photon of a given polarization could generate a single electron of a given spin orientation.
Image: artistic view of a single nanowire LED.
The single photon detectors that a currently available do not meet our requirements for the quantum optics experiments we envision. For this reason, we are developing superconducting single photon detectors with high detection efficiencies, low dark counts, high time resolution and efficient detection in the infrared. Our detectors are fabricated by patterning thin NbTiN layers on silicon substrates. We have also demonstrated that beyond single photon detection, these are also very good single electron and single alpha particle detectors.
Image: Electron microscope image of a spiraling superconducting nanowire detector.
Our superconducting nanowire detectors have also found a use as single plasmon detectors, we have demonstrated direct single plasmon detection using superconducting nanowires. This possiblity to directly detect single plasmons opens exciting possiblities where emitters, waveguides and detectors are all integrated on a chip. This ‘dark optics’ allows for a massive scaling down of quantum optics experiments and will also enable novel non-linear optics experiments making use of the very high electric field intensities at the single plasmon level.
Image: artistic view of a complete quantum plasmonics circuit.
Hybrid Atomic-Solid State Systems
We combine single quantum dots and warm rubidium vapors. This is made possible with high quality quantum dots made of GaAs in a AlGaAs matrix that emit close the transition frequency of rubidium (D2 lines). We have slowed down single photons emitted by a single quantum dot in an atomic vapor. Another possible experiment is the realization of a quantum memory where single photons from a quantum dot could be stored in an atomic ensemble.
Image: artistic view of a single quantum dot and an Rb vapor.
We acknowledge funding from ERC, FOM, NWO, ERA-NET, Horizon2020.