4 research outputs found
Protocol for generating multiphoton entangled states from quantum dots in the presence of nuclear spin fluctuations
Multi-photon entangled states are a crucial resource for many applications in
quantum information science. Semiconductor quantum dots offer a promising route
to generate such states by mediating photon-photon correlations via a confined
electron spin, but dephasing caused by the host nuclear spin environment
typically limits coherence (and hence entanglement) between photons to the spin
time of a few nanoseconds. We propose a protocol for the deterministic
generation of multi-photon entangled states that is inherently robust against
the dominating slow nuclear spin environment fluctuations, meaning that
coherence and entanglement is instead limited only by the much longer spin
time of microseconds. Unlike previous protocols, the present scheme
allows for the generation of very low error probability polarisation encoded
three-photon GHZ states and larger entangled states, without the need for spin
echo or nuclear spin calming techniques
Nitrogen-Vacancy Center Coupled to an Ultrasmall-Mode-Volume Cavity: A High-Efficiency Source of Indistinguishable Photons at 200 K
Solid state atom-like systems have great promise for linear optic quantum
computing and quantum communication but are burdened by phonon sidebands and
broadening due to surface charges. Nevertheless, coupling to a small mode
volume cavity would allow high rates of extraction from even highly dephased
emitters. We consider the nitrogen vacancy centre in diamond, a system
understood to have a poor quantum optics interface with highly distinguishable
photons, and design a silicon nitride cavity that allows 99 % efficient
extraction of photons at 200 K with an indistinguishability of > 50%,
improvable by external filtering. We analyse our design using FDTD simulations,
and treat optical emission using a cavity QED master equation valid at and
beyond strong coupling and which includes both ZPL broadening and sideband
emission. The simulated design is compact (< 10 um), and owing to its planar
geometry, can be fabricated using standard silicon processes. Our work
therefore points towards scalable fabrication of non-cryogenic atom-like
efficient sources of indistinguishable photons.Comment: 7 pages, 7 figures. Results for 3-level Jahn-Teller dephasing and
explicit effects of the LDOS on the sideband adde
Protocol for generation of high-dimensional entanglement from an array of non-interacting photon emitters
Encoding high-dimensional quantum information into single photons can provide
a variety of benefits for quantum technologies, such as improved noise
resilience. However, the efficient generation of on-demand, high-dimensional
entanglement was thought to be out of reach for current and near-future
photonic quantum technologies. We present a protocol for the near-deterministic
generation of -photon, -dimensional photonic Greenberger-Horne-Zeilinger
(GHZ) states using an array of non-interacting single-photon emitters. We
analyse the impact on performance of common sources of error for quantum
emitters, such as photon spectral distinguishability and temporal mismatch, and
find they are readily correctable with time-resolved detection to yield high
fidelity GHZ states of multiple qudits. When applied to a quantum key
distribution scenario, our protocol exhibits improved loss tolerance and key
rates when increasing the dimensionality beyond binary encodings.Comment: 15 pages, 6 figure