111 research outputs found
Frequency-encoded linear cluster states with coherent Raman photons
Entangled multi-qubit states are an essential resource for quantum
information and computation. Solid-state emitters can mediate interactions
between subsequently emitted photons via their spin, thus offering a route
towards generating entangled multi-photon states. However, existing schemes
typically rely on the incoherent emission of single photons and suffer from
severe practical limitations, for self-assembled quantum dots most notably the
limited spin coherence time due to Overhauser magnetic field fluctuations. We
here propose an alternative approach of employing spin-flip Raman scattering
events of self-assembled quantum dots in Voigt geometry. We argue that weakly
driven hole spins constitute a promising platform for the practical generation
of frequency-entangled photonic cluster states
Quantum-dot gain without inversion:Effects of dark plasmon-exciton hybridization
We propose an initial-state-dependent quantum-dot gain without population inversion in the vicinity of a resonant metallic nanoparticle. The gain originates from the hybridization of a dark plasmon-exciton and is accompanied by efficient energy transfer from the nanoparticle to the quantum dot. This hybridization of the dark plasmon-exciton, attached to the hybridization of the bright plasmon-exciton, strengthens nonlinear light-quantum emitter interactions at the nanoscale, thus the spectral overlap between the dark and the bright plasmons enhances the gain effect. This hybrid system has potential applications in ultracompact tunable quantum devices.Physics, Condensed MatterSCI(E)[email protected]
Polarized linewidth-controllable double-trapping electromagnetically induced transparency spectra in a resonant plasmon nanocavity
Surface plasmons with ultrasmall optical mode volume and strong near field enhancement can be used to realize nanoscale light-matter interaction. Combining surface plasmons with the quantum system provides the possibility of nanoscale realization of important quantum optical phenomena, including the electromagnetically induced transparency (EIT), which has many applications in nonlinear quantum optics and quantum information processing. Here, using a custom-designed resonant plasmon nanocavity, we demonstrate polarized position-dependent linewidth-controllable EIT spectra at the nanoscale. We analytically obtain the double coherent population trapping conditions in a double-L quantum system with crossing damping, which give two transparent points in the EIT spectra. The linewidths of the three peaks are extremely sensitive to the level spacing of the excited states, the Rabi frequencies and detunings of pump fields, and the Purcell factors. In particular the linewidth of the central peak is exceptionally narrow. The hybrid system may have potential applications in ultra-compact plasmon-quantum devices.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000325349300008&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Multidisciplinary SciencesSCI(E)PubMed11ARTICLE2879
Method of images applied to driven solid-state emitters
Increasing the collection efficiency from solid-state emitters is an
important step towards achieving robust single photon sources, as well as
optically connecting different nodes of quantum hardware. A metallic substrate
may be the most basic method of improving the collection of photons from
quantum dots, with predicted collection efficiency increases of up to 50%. The
established 'method-of-images' approach models the effects of a reflective
surface for atomic and molecular emitters by replacing the metal surface with a
second fictitious emitter which ensures appropriate electromagnetic boundary
conditions. Here, we extend the approach to the case of driven solid-state
emitters, where exciton-phonon interactions play a key role in determining the
optical properties of the system. We derive an intuitive polaron master
equation and demonstrate its agreement with the complementary half-sided cavity
formulation of the same problem. Our extended image approach offers a
straightforward route towards studying the dynamics of multiple solid-state
emitters near a metallic surface
Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, Magneto-optics and Charge tuning
Transition metal dichalcogenide monolayers such as MoSe2,MoS2 and WSe2 are
direct bandgap semiconductors with original optoelectronic and spin-valley
properties. Here we report spectrally sharp, spatially localized emission in
monolayer MoSe2. We find this quantum dot like emission in samples exfoliated
onto gold substrates and also suspended flakes. Spatial mapping shows a
correlation between the location of emitters and the existence of wrinkles
(strained regions) in the flake. We tune the emission properties in magnetic
and electric fields applied perpendicular to the monolayer plane. We extract an
exciton g-factor of the discrete emitters close to -4, as for 2D excitons in
this material. In a charge tunable sample we record discrete jumps on the meV
scale as charges are added to the emitter when changing the applied voltage.
The control of the emission properties of these quantum dot like emitters paves
the way for further engineering of the light matter interaction in these
atomically thin materials.Comment: 5 pages, 2 figure
Voltage-Controlled Optics of a Quantum Dot
We show how the optical properties of a single semiconductor quantum dot can
be controlled with a small dc voltage applied to a gate electrode. We find that
the transmission spectrum of the neutral exciton exhibits two narrow lines with
eV linewidth. The splitting into two linearly polarized
components arises through an exchange interaction within the exciton. The
exchange interaction can be turned off by choosing a gate voltage where the dot
is occupied with an additional electron. Saturation spectroscopy demonstrates
that the neutral exciton behaves as a two-level system. Our experiments show
that the remaining problem for manipulating excitonic quantum states in this
system is spectral fluctuation on a eV energy scale.Comment: 4 pages, 4 figures; content as publishe
Fundamental Limits to Coherent Photon Generation with Solid-State Atomlike Transitions
Coherent generation of indistinguishable single photons is crucial for many
quantum communication and processing protocols. Solid-state realizations of
two-level atomic transitions or three-level spin- systems offer
significant advantages over their atomic counterparts for this purpose, albeit
decoherence can arise due to environmental couplings. One popular approach to
mitigate dephasing is to operate in the weak excitation limit, where excited
state population is minimal and coherently scattered photons dominate over
incoherent emission. Here we probe the coherence of photons produced using
two-level and spin- solid-state systems. We observe that the coupling
of the atomic-like transitions to the vibronic transitions of the crystal
lattice is independent of driving strength and detuning. We apply a polaron
master equation to capture the non-Markovian dynamics of the ground state
vibrational manifolds. These results provide insight into the fundamental
limitations for photon coherence from solid-state quantum emitters, with the
consequence that deterministic single-shot quantum protocols are impossible and
inherently probabilistic approaches must be embraced.Comment: 16 pages [with supplementary information], 8 figure
Atomically-thin quantum dots integrated with lithium niobate photonic chips
The electro-optic, acousto-optic and nonlinear properties of lithium niobate
make it a highly versatile material platform for integrated quantum photonic
circuits. A prerequisite for quantum technology applications is the ability to
efficiently integrate single photon sources, and to guide the generated photons
through ad-hoc circuits. Here we report the integration of quantum dots in
monolayer WSe2 into a Ti in-diffused lithium niobate directional coupler. We
investigate the coupling of individual quantum dots to the waveguide mode,
their spatial overlap, and the overall efficiency of the hybrid-integrated
photonic circuit
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