Stimulated Brillouin scattering (SBS) based slow light is considered for application to squint-free (true time delay)
steering of phased array radar antennae. Results are presented on true time delay radar requirements, including delay
precision and bandwidth. We experimentally investigated the level of delay precision that exists in actual slow-light
systems (based on Brillouin scattering). The practical use of SBS to meet the necessary requirements for radar use is
discussed.
Seeding Brillouin scattering with a sufficiently efficient source of coherent phonons has the potential to produce
energy-sensitive photon detectors. Based on this idea, we propose and analyze some possible designs for such a
detector.
The Stern-Gerlach (SG) apparatus for measuring the spin of an uncharged spin-1/2 particle is the archetypal quantum
sensing device. We study this device for the new problem of measuring the spin of a particle that is coupled externally to
another particle. Specifically, we treat two coupled particles in which a single particle is measured by the SG device
while the other is not. We show simulations of how the binding energy associated with the external coupling is
completely converted to potential energy and kinetic energy as the single particle separates spatially within the magnetic
field of the SG device. Additionally we show simulations of how the initial particle acceleration within the SG devices
relates to the coupling, the quantum state of the two-particle system, and the initial spatial dispersion of the particle
within the SG device. The results of our analysis, though obtained specifically for the SG apparatus, may be generic to
other quantum measurement devices with similar external coupling.
Application of slow light linear delay to squint-free (true-time delay) steering of phased array radar antennae
is discussed. Theoretical analysis is provided on true-time delay radar requirements, including delay precision,
amplitude precision, and bandwidth. We also discuss an improvement to the slow light technique based on
stimulated Brillouin scattering by using a Faraday rotator mirror that provides temporally stable, linear (with
pump power) delay, applicable to practical implementations. Future directions are considered.
Reduced density matrix descriptions are developed for linear and non-linear electromagnetic interactions of
moving atomic systems, taking into account applied magnetic fields. Atomic collision processes are treated as
environmental interactions. Applications of interest include electromagnetically induced transparency and related pump-probe
optical phenomena in atomic vapors. Time-domain (equation-of-motion) and frequency-domain (resolvent-operator)
formulations are developed in a unified manner. The standard Born (lowest-order perturbation-theory) and
Markov (short-memory-time) approximations are systematically introduced within the framework of the general nonperturbative
and non-Markovian formulations. A preliminary semiclassical treatment of the electromagnetic interaction
is introduced. However, the need for a fully quantum mechanical approach is emphasized. Compact Liouville-space
operator expressions are derived for the linear and the general (n'th order) non-linear electromagnetic-response tensors
occurring in a perturbation-theory treatment of the electromagnetic interaction. These expressions can be evaluated for
coherent initial atomic excitations and for the full tetradic-matrix form of the Liouville-space self-energy operator
representing the environmental interactions in the Markov approximation. Intense-field electromagnetic interactions can
be treated by means of an alternative method, which is based on a Liouville-space Floquet representation of the reduced
density operator. Collisional interactions between atoms in a vapor can be treated in various approximations for the self-energy
operator and the influence of Zeeman coherences on the electromagnetic response can be incorporated.
Liouville-space (reduced-density-operator) descriptions are developed for resonant and coherent electromagnetic interactions of quantized electronic systems, taking into account environmental decoherence and relaxation phenomena. Applications of interest include electromagnetically-induced transparency and related pump-probe optical phenomena in many-electron atomic systems (in electron-ion beam interactions, gases, and high-temperature plasmas) and
semiconductor materials (bulk crystals and nanostructures). Time-domain (equation-of-motion) and frequency-domain (resolvent-operator) formulations are developed in a unified manner. The standard Born (lowest-order perturbationtheory) and Markov (short-memory-time) approximations are systematically introduced within the framework of the general non-perturbative and non-Markovian formulations. A preliminary semiclassical description of the entire electromagnetic interaction is introduced. Compact Liouville-space operator expressions are derived for the linear and the general (n'th order) non-linear electromagnetic-response tensors occurring in a perturbation-theory treatment of the semiclassical electromagnetic interaction. These expressions can be evaluated for coherent initial electronic excitations and for the full tetradic-matrix form of the Liouville-space self-energy operator representing the environmental interactions in the Markov approximation. Intense-field electromagnetic interactions are treated by means of an alternative, non-perturbative method, which is based on a Liouville-space Floquet-Fourier representation of the reduced density operator. Electron-electron quantum correlations are treated by the introduction of a cluster decomposition of the reduced density operator and a coupled hierarchy of reduced-density-operator equations.
We propose a "channelization" architecture to achieve wide-band
electromagnetically induced transparency (EIT) and ultra-slow light
propagation in atomic Rb-87 vapors. EIT and slow light are achieved
by shining a strong, resonant "pump" laser on the atomic medium,
which allows slow and unattenuated propagation of a weaker "signal"
beam, but only when a two-photon resonance condition is satisfied.
Our wideband architecture is accomplished by dispersing a wideband
signal spatially, transverse to the propagation direction, prior to
entering the atomic cell. When particular Zeeman sub-levels are used
in the EIT system, then one can introduce a magnetic field with a
linear gradient such that the two-photon resonance condition is
satisfied for each individual frequency component. Because slow
light is a group velocity effect, utilizing differential phase
shifts across the spectrum of a light pulse, one must then introduce
a slight mismatch from perfect resonance to induce a delay. We
present a model which accounts for diffusion of the atoms in the
varying magnetic field as well as interaction with levels outside
the ideal three-level system on which EIT is based. We find the
maximum delay-bandwidth product decreases with bandwidth, and that
delay-bandwidth product 1 should be achievable with bandwidth 50 MHz
(5 ns delay). This is a large improvement over the 1 MHz bandwidths
in conventional slow light systems and could be of use in signal
processing applications.
Weak measurement is a technique whereby the coupling between the measuring device and the observable is sufficiently weak that the uncertainty in a single measurement is large compared with the separation between the eigenvalues of the observable. It is found here that weak measurement can be achieved with a single qubit. An additional feature of using single qubits as weak measurement devices is that the entanglement that results between the measured and measuring qubits can be easily quantified. An analysis is provided of the effect of entanglement using an example similar to the Hardy paradox of double interferometers with positron-electron annihilation.
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