17 research outputs found
Contribution of drifting carriers to the Casimir-Lifshitz and Casimir-Polder interactions with semiconductor materials
We develop a new theory for Casimir-Lifshitz and Casimir-Polder interactions
with semiconductor surfaces that takes into account charge drift in the bulk
material. The corresponding frequency-dependent dispersion relations describe a
crossover between Lifshitz results for dielectrics and for good conductors. In
the quasi-static limit, our calculated reflection amplitudes coincide with
those recently computed to account for Debye screening in the thermal Lifshitz
force with conducting surfaces with small density of carriers.Comment: 4 pages version 2: improved discussion of perfect conductor and
perfect dielectric limits. Version 3; includes discussion of limits of
applicability of the analysis. Version $; updated reference
On the use of dielectric elements in axion searches with microwave resonant cavities
This study explores the primary effects of dielectric materials in a resonant
cavity-based search for axion dark matter. While dielectrics prove beneficial
in numerous cases, their incorporation may lead to less-than-optimal
performance, especially for the lowest TM mode. Additionally, the stronger
confinement of the electric field inside the dielectrics can exacerbate mode
mixings, in particular for higher-order modes. Case studies have been carried
out using a combination of analytical solutions and numerical simulations. The
findings indicate dielectric cavities employing the mode
experience a significant reduction in sensitivity when compared to a similar
search conducted in a cavity at equivalent frequency using no dielectrics.Comment: 10 pages, 7 figure
Practical quantum cryptography for secure free-space communications
Quantum cryptography is an emerging technology in which two parties may
simultaneously generate shared, secret cryptographic key material using the
transmission of quantum states of light. The security of these transmissions is
based on the inviolability of the laws of quantum mechanics and
information-theoretically secure post-processing methods. An adversary can
neither successfully tap the quantum transmissions, nor evade detection, owing
to Heisenberg's uncertainty principle. In this paper we describe the theory of
quantum cryptography, and the most recent results from our experimental
free-space system with which we have demonstrated for the first time the
feasibility of quantum key generation over a point-to-point outdoor atmospheric
path in daylight. We achieved a transmission distance of 0.5 km, which was
limited only by the length of the test range. Our results provide strong
evidence that cryptographic key material could be generated on demand between a
ground station and a satellite (or between two satellites), allowing a
satellite to be securely re-keyed on orbit. We present a feasibility analysis
of surface-to-satellite quantum key generation.Comment: 12 pages, 4 figure
Computation of Casimir forces for dielectrics or intrinsic semiconductors based on the Boltzmann transport equation
The interaction between drifting carriers and traveling electromagnetic waves
is considered within the context of the classical Boltzmann transport equation
to compute the Casimir-Lifshitz force between media with small density of
charge carriers, including dielectrics and intrinsic semiconductors. We expand
upon our previous work [Phys. Rev. Lett. {\bf 101}, 163203 (2008)] and derive
in some detail the frequency-dependent reflection amplitudes in this theory and
compute the corresponding Casimir free energy for a parallel plate
configuration. We critically discuss the the issue of verification of the
Nernst theorem of thermodynamics in Casimir physics, and explicity show that
our theory satisfies that theorem. Finally, we show how the theory of drifting
carriers connects to previous computations of Casimir forces using spatial
dispersion for the material boundaries.Comment: 9 pages, 2 figures; Contribution to Proceedings of "60 Years of the
Casimir Effect", Brasilia, June 200