18 research outputs found
Comprehensive scheme for identifying defects in solid-state quantum systems
A solid-state quantum emitter is one of the indispensable components for
optical quantum technologies. Ideally, an emitter should have a compatible
wavelength for efficient coupling to other components in a quantum network. It
is therefore essential to understand fluorescent defects that lead to specific
emitters. In this work, we employ density functional theory (DFT) to
demonstrate the calculation of the complete optical fingerprints of quantum
emitters in the two-dimensional material hexagonal boron nitride. These
emitters are of great interest, yet many of them are still to be identified.
Our results suggest that instead of comparing a single optical property, such
as the commonly used zero-phonon line energy, multiple properties should be
used when comparing theoretical simulations to the experiment. This way, the
entire electronic structure can be predicted and quantum emitters can be
designed and tailored. Moreover, we apply this approach to predict the
suitability for using the emitters in specific quantum applications,
demonstrating through the examples of the Al and
PV defects. We therefore combine and apply DFT
calculations to identify quantum emitters in solid-state crystals with a lower
risk of misassignments as well as a way to design and tailor optical quantum
systems. This consequently serves as a recipe for classification and the
generation of universal solid-state quantum emitter systems in future hybrid
quantum networks.Comment: 10 pages, 4 figure
Identifying electronic transitions of defects in hexagonal boron nitride for quantum memories
A quantum memory is a crucial keystone for enabling large-scale quantum
networks. Applicable to the practical implementation, specific properties,
i.e., long storage time, selective efficient coupling with other systems, and a
high memory efficiency are desirable. Though many quantum memory systems have
been developed thus far, none of them can perfectly meet all requirements. This
work herein proposes a quantum memory based on color centers in hexagonal boron
nitride (hBN), where its performance is evaluated based on a simple theoretical
model of suitable defects in a cavity. Employing density functional theory
calculations, 257 triplet and 211 singlet spin electronic transitions have been
investigated. Among these defects, we found that some defects inherit the
electronic structures desirable for a Raman-type quantum memory and
optical transitions can couple with other quantum systems. Further, the
required quality factor and bandwidth are examined for each defect to achieve a
95\% writing efficiency. Both parameters are influenced by the radiative
transition rate in the defect state. In addition, inheriting triplet-singlet
spin multiplicity indicates the possibility of being a quantum sensing, in
particular, optically detected magnetic resonance. This work therefore
demonstrates the potential usage of hBN defects as a quantum memory in future
quantum networks.Comment: 12 pages, 6 figure
Localized creation of yellow single photon emitting carbon complexes in hexagonal boron nitride
Single photon emitters in solid-state crystals have received a lot of
attention as building blocks for numerous quantum technology applications.
Fluorescent defects in hexagonal boron nitride (hBN) stand out due to their
high luminosity and robust operation at room temperature. The identical emitter
fabrication at pre-defined sites is still challenging, which hampers the
integration of these defects in optical systems and electro-optical devices.
Here, we demonstrate the localized fabrication of hBN emitter arrays by
electron beam irradiation using a standard scanning electron microscope with
deep sub-micron lateral precision. The emitters are created with a high yield
and a reproducible spectrum peaking at 575 nm. Our measurements of optically
detected magnetic resonance have not revealed any addressable spin states.
Using density functional theory, we attribute the experimentally observed
emission lines to carbon-related defects, which are activated by the electron
beam. Our scalable approach provides a promising pathway for fabricating room
temperature single photon emitters in integrated quantum devices
Modeling of price and profit in coupled-ring networks
We study the behaviors of magnetization, price, and profit profiles in ring networks in
the presence of the external magnetic field. The Ising model is used to determine the
state of each node, which is mapped to the buy-or-sell state in a financial market, where
+1 is identified as the buying state, and −1 as the selling state. Price and profit mechanisms are modeled based
on the assumption that price should increase if demand is larger than supply, and it
should decrease otherwise. We find that the magnetization can be induced between two rings
via coupling links, where the induced magnetization strength depends on the number of the
coupling links. Consequently, the price behaves linearly with time, where its rate of
change depends on the magnetization. The profit grows like a quadratic polynomial with
coefficients dependent on the magnetization. If two rings have opposite direction of net
spins, the price flows in the direction of the majority spins, and the network with the
minority spins gets a loss in profit