780 research outputs found
Terahertz quantum cryptography
A well-known empirical rule for the demand of wireless communication systems is that of Edholm's law of bandwidth. It states that the demand for bandwidth in wireless short-range communications doubles every 18 months. With the growing demand for bandwidth and the decreasing cell size of wireless systems, terahertz (THz) communication systems are expected to become increasingly important in modern day applications. With this expectation comes the need for protecting users' privacy and security in the best way possible. With that in mind, we show that quantum key distribution can operate in the THz regime and we derive the relevant secret key rates against realistic collective attacks. In the extended THz range (from 0.1 to 50 THz), we find that below 1 THz, the main detrimental factor is thermal noise, while at higher frequencies it is atmospheric absorption. Our results show that high-rate THz quantum cryptography is possible over distances varying from a few meters using direct reconciliation, to about 220m via reverse reconciliation. We also give a specific example of the physical hardware and architecture that could be used to realize our THz quantum key distribution scheme
Inter-satellite Quantum Key Distribution at Terahertz Frequencies
Terahertz (THz) communication is a topic of much research in the context of
high-capacity next-generation wireless networks. Quantum communication is also
a topic of intensive research, most recently in the context of space-based
deployments. In this work we explore the use of THz frequencies as a means to
achieve quantum communication within a constellation of micro-satellites in
Low-Earth-Orbit (LEO). Quantum communication between the micro-satellite
constellation and high-altitude terrestrial stations is also investigated. Our
work demonstrates that THz quantum entanglement distribution and THz quantum
key distribution are viable deployment options in the micro-satellite context.
We discuss how such deployment opens up the possibility for simpler integration
of global quantum and wireless networks. The possibility of using THz
frequencies for quantum-radar applications in the context of LEO deployments is
briefly discussed.Comment: 7 pages, 6 figure
Control of electronic transport in graphene by electromagnetic dressing
We demonstrated theoretically that the renormalization of the electron energy
spectrum near the Dirac point of graphene by a strong high-frequency
electromagnetic field (dressing field) drastically depends on polarization of
the field. Namely, linear polarization results in an anisotropic gapless energy
spectrum, whereas circular polarization leads to an isotropic gapped one. As a
consequence, the stationary (dc) electronic transport in graphene strongly
depends on parameters of the dressing field: A circularly polarized field
monotonically decreases the isotropic conductivity of graphene, whereas a
linearly polarized one results in both giant anisotropy of conductivity (which
can reach thousands of percents) and the oscillating behavior of the
conductivity as a function of the field intensity. Since the predicted
phenomena can be observed in a graphene layer irradiated by a monochromatic
electromagnetic wave, the elaborated theory opens a substantially new way to
control electronic properties of graphene with light.Comment: Published versio
Tailoring and enhancing spontaneous two-photon emission processes using resonant plasmonic nanostructures
The rate of spontaneous emission is known to depend on the environment of a
light source, and the enhancement of one-photon emission in a resonant cavity
is known as the Purcell effect. Here we develop a theory of spontaneous
two-photon emission for a general electromagnetic environment including
inhomogeneous dispersive and absorptive media. This theory is used to evaluate
the two-photon Purcell enhancement in the vicinity of metallic nanoparticles
and it is demonstrated that the surface plasmon resonances supported by these
particles can enhance the emission rate by more than two orders of magnitude.
The control over two-photon Purcell enhancement given by tailored
nanostructured environments could provide an emitter with any desired spectral
response and may serve as an ultimate route for designing light sources with
novel properties
Photonic crystal chips for optical interconnects and quantum information processing
We have recently demonstrated a number of functional photonic crystals devices and circuits, including an ultrafast, room temperature, low threshold, nanocavity laser with the direct modulation speed approaching 1 THz, an all-optical switch controlled with 60 fJ pulses and with the speed exceeding 200Hz, and a local, reversible tuning of individual quantum dots on a photonic crystal chip by up to 1.8nm, which was then used to tune single quantum dots into strong coupling with a photonic crystal cavity and to achieve a giant optical nonlinearity
Quantum Technology: The Second Quantum Revolution
We are currently in the midst of a second quantum revolution. The first
quantum revolution gave us new rules that govern physical reality. The second
quantum revolution will take these rules and use them to develop new
technologies. In this review we discuss the principles upon which quantum
technology is based and the tools required to develop it. We discuss a number
of examples of research programs that could deliver quantum technologies in
coming decades including; quantum information technology, quantum
electromechanical systems, coherent quantum electronics, quantum optics and
coherent matter technology.Comment: 24 pages and 6 figure
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