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We demonstrate all-optical coherent manipulation of a quantum dot spin through coherent population trapping with a sub-linewidth spin splitting, enabled by the hyperfine interaction with a mesoscopic nuclear spin ensemble.
Entanglement plays a central role in fundamental tests of quantum mechanics as well as in the burgeoning field of quantum information processing. Particularly in the context of quantum networks and communication, an outstanding challenge is the efficient generation of entanglement between stationary (spin) and flying (photon) qubits. In this talk, I will first show the observation of quantum entanglement...
Recent advances in quantum dot based quantum technology are presented: scalable fabrication of bright sources of single photons or entangled photon pairs, optical non-linearities at the few photon scales and first implementations of quantum gates.
The entanglement of photons from a biexciton cascade is strongly diminished by exciton fine-structure splitting. We demonstrate an optical feedback mechanism to counteract this loss and to control the photon entanglement.
We propose a novel scheme for a single-shot, fast (10s of nanoseconds), high fidelity (99.95%) quantum non-demolition (QND) readout of quantum dot (QD) electron spins based on their spin-dependent Coulomb exchange interaction with optically-excited quantum well (QW) microcavity exciton-polaritons.
A unique experimental setup combining short pulse pump-probe and FROG characterization, enables control by light pulses over the electronic quantum state, and a direct observation of the wavefunction decoherence in a room-temperature semiconductor laser amplifier.
Boron-doped super-high density nano-crystalline Si quantum dot thin film is demonstrated by utilizing a gradient Si-rich oxide multilayer structure. The boron doping effect and its significant influence on photovoltaic properties are observed and discussed.
Semiconductor quantum dot based single photon emitters are a critical component for quantum cryptography. In this work, we show a scalable single-photon emitter structure using site-controlled elliptical quantum dots with a controllable and tunable output polarization.
We have developed an optical switch with a quantum dot in a high Q-factor microcavity. Experimental reflectivity spectroscopy fitted by a semi-analytical model estimates the intracavity photon number required to switch the device as 0.13.
We report single-photon emission from electrically driven site-controlled InGaN/GaN dot-in-nanowires, fabricated from a planar single InGaN quantum well LED using a top-down approach. Each dot-in-nanowire's formation site, diameter, height and material compositions were precisely controlled.
One of the central assumptions in quantum electrodynamics is to invoke the dipole approximation because (quantum) emitters are much smaller than the wavelength of light. The main consequence is that only the electric dipole plays a role in light-matter interactions at optical frequencies. In this paper we show that semiconductor quantum dots possess large magnetic-dipole and electric-quadrupole moments,...
We present an investigation of the far-off-resonant coupling between a semiconductor quantum dot and a cavity. We show that the enhanced coupling observed in experiments is explained by Coulomb interactions with wetting layer carriers.
Ga(In)N nanowires and Ga(In)N quantum disks can be grown defect-free on silicon with p- and n-doping to form diodes. We will describe the characteristics of light-emitting diodes and electrically injected single nanowire single photon sources.
Using a realistic quantum master equation we show that the Mollow triplet of a quantum dot can be tuned by adjusting its local density of states via biasing of a graphene monolayer.
We demonstrate 2D coherent spectroscopy of CdSe/ZnS nanocrystals and measure the exciton homogeneous linewidth. The 2D spectra also reveal an off-diagonal peak that oscillates as a function of the waiting time T.
We present a new technique for Multi-Dimensional Coherent spectroscopy of nano-structures. We measure the Four-Wave Mixing (FWM) amplitude and phase via photocurrent detection. The measurement is suitable for any nano-structures that can be electrically contacted.
We demonstrate spontaneous emission enhancement (by an average factor of 4.6) and saturable absorption of cadmium selenide colloidal quantum dots coupled to a nanobeam photonic crystal cavity, at room temperature.
To improve poor emissions from quantum wires and dots in GaN pyramidal structure, we introduced silver film on pyramid structure. Due to the pyramidal geometry, we could successfully control the spontaneous emission of these structures.
Robust excitation of an exciton state via adiabatic rapid passage is demonstrated in a single InGaAs quantum dot using subpicosecond optical pulses. A chirp sign dependence of the transfer efficiency indicates dephasing tied to phonons.
A quantum-dot tapered waveguide external cavity laser is presented, with 100nm tunability. At 1230nm, a maximum power of 0.62W was achieved, representing a 16-fold increase compared with equivalent narrow-ridge lasers at the same current density.
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