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Showing papers on "Interference (wave propagation) published in 2001"


Journal ArticleDOI
07 Jun 2001-Nature
TL;DR: This work describes an example of a coherent molecular electronic device whose behaviour is explicitly dependent on quantum interference between propagating electron waves—a Fabry–Perot electron resonator based on individual single-walled carbon nanotubes with near-perfect ohmic contacts to electrodes.
Abstract: The behaviour of traditional electronic devices can be understood in terms of the classical diffusive motion of electrons. As the size of a device becomes comparable to the electron coherence length, however, quantum interference between electron waves becomes increasingly important, leading to dramatic changes in device properties. This classical-to-quantum transition in device behaviour suggests the possibility for nanometer-sized electronic elements that make use of quantum coherence. Molecular electronic devices are promising candidates for realizing such device elements because the electronic motion in molecules is inherently quantum mechanical and it can be modified by well defined chemistry. Here we describe an example of a coherent molecular electronic device whose behaviour is explicitly dependent on quantum interference between propagating electron waves-a Fabry-Perot electron resonator based on individual single-walled carbon nanotubes with near-perfect ohmic contacts to electrodes. In these devices, the nanotubes act as coherent electron waveguides, with the resonant cavity formed between the two nanotube-electrode interfaces. We use a theoretical model based on the multichannel Landauer-Buttiker formalism to analyse the device characteristics and find that coupling between the two propagating modes of the nanotubes caused by electron scattering at the nanotube-electrode interfaces is important.

908 citations


Journal ArticleDOI
TL;DR: This work presents an architecture that is optimal, in the sense of maximum link spectral efficiency, inThe presence of spatially colored interference, and compares it, under various propagation conditions, to other adaptive-antenna techniques with equal number of antennas.
Abstract: Previous information theory results have demonstrated the enormous capacity potential of wireless communication systems with multiple transmit and receive antennas. To exploit this potential, a number of space-time architectures have been proposed which transmit parallel data streams, simultaneously and on the same frequency, in a multiple-input multiple-output fashion. With sufficient multipath propagation, these different streams can be separated at the receiver. Mostly, these space-time schemes have been studied only in the presence of spatially white noise. We present an architecture that is optimal, in the sense of maximum link spectral efficiency, in the presence of spatially colored interference. We evaluate this new architecture and compare it, under various propagation conditions, to other adaptive-antenna techniques with equal number of antennas.

313 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed to use nonradiating electromagnetic surface waves that propagate along thin metallic strips for long-distance RF energy transfer, which is simple, inexpensive, lightweight, and has low attenuation.
Abstract: Electromagnetic RF energy can be transported over a kilometer or more using antennas, but the efficiency is low unless the injecting and receiving antennas are extremely large. Other means of transporting RF energy such as waveguides and coaxial lines are cumbersome, heavy, costly, and suffer large attenuation. This paper offers a different system for long-distance RF transportation. The key is to use nonradiating electromagnetic surface waves that propagate along thin metallic strips. This means of moving RF energy between two points is simple, inexpensive, lightweight, and has low attenuation. For example, the attenuation is less than 2 dB/km for an Al foil 6-cm wide and 0.002-cm thick. Thus, efficient guidance of surface waves over distances of many kilometers requires neither large antennas, waveguides, nor coaxial lines. Moreover, electric interference with the surroundings is minimized due to the large reduction in the radial extension of the electric field, and the conversion of the radiating electromagnetic waves to surface waves and back is efficient (up to 90%).

291 citations


Journal ArticleDOI
TL;DR: In this article, the generation of optical vortices by three plane waves interference is studied and the necessary conditions for such process are derived and the net structure of optical Vortices generated in this way is analyzed.

202 citations


Patent
16 Oct 2001
TL;DR: In this article, the authors propose to estimate the pilot interference from each interference multipath based on the spreading sequence for the interfering multipath and the despreading sequence of the desired multipath.
Abstract: Techniques for canceling pilot interference in a wireless (e.g., CDMA) communication system. A received signal typically includes a number of signal instances (i.e., multipaths). For each multipath desired to be processed, the other multipaths act as interference on the desired multipath. If the pilot is generated based on a known data pattern (e.g., all zeros) and covered with a known channelization code (e.g., a Walsh code of zero), then the pilot in an interfering multipath may be estimated as the spreading sequence at a time offset corresponding to the arrival time of that multipath. The pilot interference from each interference multipath may be estimated based on the spreading sequence for the interfering multipath and the despreading sequence for the desired multipath. The total pilot interference from a number of interfering multipaths may be subtracted from the data component in the desired multipath to provide pilot-canceled data having improved performance.

168 citations


Journal ArticleDOI
TL;DR: In this paper, the capability of two different, recently proposed semiclassical (SC) forward-backward (FB) initial value representations (IVR) to describe quantum interference and coherence effects is investigated.
Abstract: The capability of two different, recently proposed semiclassical (SC) forward–backward (FB) initial value representations (IVR) to describe quantum interference and coherence effects is investigated. It is shown that depending on the way the observable under consideration is represented by unitary operators one can obtain rather different results. Although the FB-IVR based on an integral representation as a rule is capable of describing quantum interference, a closer analysis reveals that it depends on the observable under consideration if all interference that can be described semiclassically is actually included in the calculation. To overcome this problem a new, generalized FB-IVR method (GFB-IVR) is proposed, which combines the capability of the SC-IVR to describe quantum interference effects independent of the observable and the better convergence properties of the FB-IVR. The performance of this new approach is studied in some detail. In particular, it is shown that the GFB-IVR can describe both the...

163 citations


Patent
Stefan Franz1, Matthias Fleischer1
29 Mar 2001
TL;DR: In this article, an apparatus for an interferometric measuring device consisting of a first and a second interferometer was proposed, where the optical path lengths of the two partial beams are different to compensate for optical path difference between the two interferometers.
Abstract: The invention relates to an apparatus for an interferometric measuring device comprising a first interferometer and a second interferometer, wherein short-coherent radiation is fed to the first interferometer by means of a radiation source, which radiation is split into two partial beams by means of a first beam splitter, and wherein the optical path length is longer in one partial beam than in the other partial beam to the effect that the optical path difference is greater than the coherence length of the radiation, wherein the two partial beams are recombined prior to exit from the first interferometer and are fed to the second interferometer, which splits the radiation into two further partial beams, wherein the optical path lengths of the two partial beams are different to the effect that the optical path difference written in the first interferometer is compensated again, wherein the optical path length for a respective partial beam in the first and second interferometer can be set by means of at least one moveable optical component and the moveable optical components are mechanically coupled to one another. The invention furthermore relates to a method for compensating for an optical path difference in such an interferometric measuring device, wherein the optical path differences between the partial beams in the two interferometers are altered simultaneously and by the same magnitude by means of mechanically coupled moveable optical components. It is thereby possible to vary path differences in the partial beams of the interferometers in one work step, the conditions for forming interference still being complied with.

131 citations


Proceedings ArticleDOI
21 Jul 2001
TL;DR: A simulation environment for modeling interference based on detailed MAC and PHY models is presented and this framework is then used to evaluate the impact of interference on the performance of Bluetooth and IEEE 802.11.
Abstract: The emergence of several radio technologies such as Bluetooth, and IEEE 802.11 operating in the 2.4 GHz unlicensed ISM frequency band may lead to signal interference and result in significant performance degradation when devices are co-located in the same environment. The main goal of this paper is to present a simulation environment for modeling interference based on detailed MAC and PHY models. This framework is then used to evaluate the impact of interference on the performance of Bluetooth and IEEE 802.11. We use several simulation scenarios and measure performance in terms of packet loss, residual number of errors, and access delay.

126 citations


Journal ArticleDOI
TL;DR: It is found that the arrival time difference (Delta L/c) and the time window of the coincidence counter (Delta T) are important parameters which determine the boundary between the classical and quantum regimes.
Abstract: We constructed an efficient source of photon pairs using a waveguide-type nonlinear device and performed a two-photon interference experiment with an unbalanced Michelson interferometer. As the interferometer has two arms of different lengths, photons from the short arm arrive at the detector earlier than those from the long arm. We find that the arrival time difference (Delta L/c) and the time window of the coincidence counter (Delta T) are important parameters which determine the boundary between the classical and quantum regimes. Fringes of high visibility ( 80% +/- 10%) were observed when Delta T < Delta L/c. This result is explained only by quantum theory and is clear evidence for quantum entanglement of the interferometer's optical paths.

111 citations


Patent
25 Sep 2001
TL;DR: In this article, a multi-layer-coupled surface plasmon notch filter is provided to have more than two symmetric metal-dielectric interfaces coupled with one another to produce a transmission spectral window with desired spectral profile and bandwidth.
Abstract: Devices based on surface plasmon filters having at least one metal-dielectric interface to support surface plasmon waves. A multi-layer-coupled surface plasmon notch filter is provided to have more than two symmetric metal-dielectric interfaces coupled with one another to produce a transmission spectral window with desired spectral profile and bandwidth. Such notch filters can form various color filtering devices for color flat panel displays.

95 citations


Journal ArticleDOI
Petr Hlubina1
TL;DR: In this paper, the authors measured the equalization wavelength as a function of the displacement in the Michelson interferometer by a low-resolution miniature fiber-optic spectrometer and confirmed that the group refractive index dispersion in the beam splitter made of fused silica agrees well with that resulting from the Sellmeier dispersion equation.

Journal ArticleDOI
TL;DR: This work deals with interference suppression in asynchronous direct-sequence code-division multiple-access (CDMA) systems employing binary phase-shift keying modulation and derives a new family of minimum mean-square-error detectors, which differ from their conventional counterparts in that they minimize a modified cost function.
Abstract: We deal with interference suppression in asynchronous direct-sequence code-division multiple-access (CDMA) systems employing binary phase-shift keying modulation. Such an interference may arise from other users of the network, from external low-rate systems, as well as from a CDMA network coexisting with the primary network to form a dual-rate network. We derive, for all of these cases, a new family of minimum mean-square-error detectors, which differ from their conventional counterparts in that they minimize a modified cost function. Since the resulting structure is not implementable with acceptable complexity, we also propose some suboptimum systems. The statistical analysis reveals that both the optimum and the suboptimum receivers are near-far resistant, not only with respect to the other users, but also with respect to the external interference. We also present a blind and a recursive least squares-based, decision-directed implementation of the receivers wherein only the signature and the timing of the user to be decoded and the signaling time and the frequency offset of the external interferer are assumed known. Finally, computer simulations show that the proposed adaptive algorithm outperforms the classical decision-directed RLS algorithm.

Journal ArticleDOI
Weiping Xu1, L.B. Milstein
TL;DR: This paper designs a DS-CDMA system with the capability to increase the data rate, mitigate the effect of correlation among the various subcarriers, and suppress partial-band interference, and employs a correlated subcarrier and frequency-selective fading channel model to derive the average probability of error.
Abstract: In this paper, we integrate the multicarrier signaling technique and the RAKE receiver to design a DS-CDMA system with the capability to increase the data rate, mitigate the effect of correlation among the various subcarriers, and suppress partial-band interference. In the proposed system, a data sequence is serial-to-parallel converted, and multicarrier DS-CDMA is used on each of the parallel data streams. The receiver provides a RAKE for each subcarrier, and the outputs of the RAKEs are combined by a maximal-ratio combiner. We employ a correlated subcarrier and frequency-selective fading channel model to derive the average probability of error of the system and compare the results with those of both a single carrier RAKE system and a multicarrier DS-CDMA system in a frequency selective Rayleigh fading channel with an exponential multipath intensity profile, when multiple access interference and partial-band interference are present.

01 Jan 2001
TL;DR: In this paper, a study of the natural geometric structures arising through interference, in fields of complex waves (scalars, vectors or tensors), where certain parameters describing the wave are singular.
Abstract: This thesis is a study of the natural geometric structures, arising through interference, in fields of complex waves (scalars, vectors or tensors), where certain parameters describing the wave are singular. In scalar waves, these are phase singularities (also called wave dislocations), which are also nodes (zeros of amplitude): in two dimensional fields they are points, and in three dimensions, lines. The morphology of dislocation points and lines is studied in detail, and averages of their geometrical properties (such as density, speed, curvature and twistedness) are calculated analytically for isotropically random gaussian ensembles (superpositions of plane waves equidistributed in direction, but with random phases). It is also shown how dislocation lines may be knotted and linked, and a construction of torus knots in monochromatic waves is studied in detail, using experimentally realisable beams. In vector waves, the appropriate fields are described geometrically by an ellipse at each point (the polarization ellipse). Their singularities, occurring along lines in three dimensions, are where the ellipse is circular (C lines) and linear (L lines); in two dimensional fields, possibly representing the transverse plane of paraxial polarized light waves, there are C points, but still L lines. The geometry of these singularities is considered, and analytical calculations for their densities in isotropic gaussian random vector waves are performed. The C and L singularity structures are generalised to fields of spinors using the Majorana sphere (vector fields have spin 1), and singularities in rank two tensor waves (spin 2) are briefly discussed.

Journal ArticleDOI
H.V. Poor1
TL;DR: A progression of techniques is described, in which successively more information about the spread-spectrum signal and interference is used to make improvements on the interference suppression capability via more advanced signal processing methods.
Abstract: Communication networks involving the overlay of spread-spectrum systems an narrower band services are of increasing interest as a means of producing greater efficiencies and flexibility in the use of the radio spectrum. Although spread-spectrum systems enjoy a natural immunity to interference from narrowband sources, their performance in the presence of such interference can be significantly enhanced by active suppression techniques. The study of this problem has elicited a very rich body of methodology, which has progressed over nearly 25 years from some of the simplest signal processing paradigms to some of the most advanced. This paper provides an overview of a number of these techniques, most of which have been developed over the past decade. In particular, a progression of techniques is described, in which successively more information about the spread-spectrum signal and interference is used to make improvements on the interference suppression capability via more advanced signal processing methods. These include linear predictive methods that make use of the spectral properties of the spread-spectrum and narrowband signals, nonlinear predictive methods that make use of the spectra and first-order probability distribution of these signals, linear code-aided methods that make use of the spreading codes of the signals of interest and the second-order statistics of the narrowband interference, and finally, a maximum-likelihood code-aided technique that makes use of essentially all that is known about the useful signals and interference. Performance comparisons show that moving up this progression of improved modeling is rewarded with performance gains that can be quite significant.

Proceedings ArticleDOI
21 Oct 2001
TL;DR: An acoustic echo suppression method that operates in the short-time Fourier transform (STFT) domain is described and evaluated, shown to be efficient, and a viable and robust alternative to acoustic echo cancellation methods when the computation requirements are constringent.
Abstract: We describe and evaluate an acoustic echo suppression method that operates in the short-time Fourier transform (STFT) domain The system estimates the short-time spectrum of the acoustic interference component that causes the echo at the far end and subtracts it from the short-time spectrum of the microphone input using a nonlinear spectral subtraction rule, allowing for a trade-off between speech distortion and residual rejection The interference estimator uses a set of decoupled adaptive FIR filters that operate on the STFT sub-band trajectories and that can be extended to include multiple acoustic channels The method is shown be efficient, and a viable and robust alternative to acoustic echo cancellation methods when the computation requirements are constringent

Patent
03 Jul 2001
TL;DR: In this paper, a system of etching using quantum entangled particles to get shorter interference fringes was proposed, where the interferometer is used to obtain an interference fringe and entangled photons are input to the inter-ferometer.
Abstract: A system of etching using quantum entangled particles to get shorter interference fringes An interferometer is used to obtain an interference fringe N entangled photons are input to the interferometer This reduces the distance between interference fringes by n, where again n is the number of entangled photons

Proceedings ArticleDOI
06 May 2001
TL;DR: In this paper, the free space law was used to model the propagation of short pulses in the UWB (ultra wide band) with the additional effect of transmission losses through typical home or office walls.
Abstract: Pulsed UWB (ultra wide band) signals are more nearly transient phenomena than they are continuous waves. Multipath effects for the most part manifest themselves as time delayed replicants of the pulses. Short pulses propagate with the free space law, and only when the differential delay among pulses and replicants is less than about half the pulse length do the signals exhibit destructive interference. The propagation model described here is based on the free space law with the additional effect of transmission losses through typical home or office walls. The conditions for destructive inference of pulses is also derived.

Journal ArticleDOI
TL;DR: Comparative results demonstrate how performance is affected by the introduction of intercell interference, and what is the penalty associated with the randomly spread coded DS-CDMA strategy.
Abstract: A simple multicell uplink communication model is suggested and analyzed for optimally coded randomly spread direct sequence code-division multiple access (DS-CDMA). The model adheres to Wyner's (1994) infinite linear cell-array model, according to which only adjacent-cell interference is present, and characterized by a single parameter 0/spl les//spl alpha//spl les/1. The discussion is confined to asymptotic analysis where both the number of users and the processing gain go to infinity, while their ratio goes to some finite constant. Single cell-site processing is assumed and four multiuser detection strategies are considered: the matched-filter detector, "optimum" detection with adjacent-cell interference treated as Gaussian noise, the linear minimum mean square error (MMSE) detector and a detector that performs MMSE-based successive interference cancellation for intracell users with linear MMSE processing of adjacent-cell interference. Spectral efficiency is evaluated under three power allocation policies: equal received powers (for all users), equal rates, and a maximal spectral efficiency policy. Comparative results demonstrate how performance is affected by the introduction of intercell interference, and what is the penalty associated with the randomly spread coded DS-CDMA strategy. Finally, the effect of intercell time-sharing protocols as suggested by Shamai and Wyner (1997) is also examined, and a significant system performance enhancement is observed.

Proceedings ArticleDOI
11 Jun 2001
TL;DR: It is shown that the proposed method can effectively mitigate CCI while preserving the space-time structure, thereby, significantly improving the system's interference suppression ability without significant performance degradation.
Abstract: Space-time coded OFDM is a promising scheme for future wideband multimedia wireless communication systems. The combination of space-time coding (STC) and OFDM modulation promises an enhanced performance in terms of power and spectral efficiency. However, STC transmit diversity impairs the system's interference suppression ability because each transmitter generates multiple signals that appear independent to the receiver antenna arrays. In this paper, we propose a novel CCI cancellation method employing angle diversity based on beamforming. It is shown that the proposed method can effectively mitigate CCI while preserving the space-time structure, thereby, significantly improving the system's interference suppression ability without significant performance degradation.

Journal ArticleDOI
TL;DR: This analysis shows that a fiber bundle with spacing of the order of the wavelength, which one may conveniently control by changing the recording geometry, can be formed by this means.
Abstract: A systematic analysis of interference of three noncoplanar plane waves with identical frequency is provided. This analysis shows that a fiber bundle with spacing of the order of the wavelength, which one may conveniently control by changing the recording geometry, can be formed by this means. The relation between the incident light-wave vectors and the resultant pattern is analyzed. The concept of uniform contrast for an interference pattern is introduced, and the polarization optimization approach for each beam that ensures maximum uniform contrast for each beam is also given.

Journal ArticleDOI
05 Jul 2001-Nature
TL;DR: A double-path quantum interference experiment involving a liquid: superfluid 3He is reported, and the classic interference pattern with periodicity determined by the 3He quantum of circulation is found.
Abstract: Celebrated interference experiments have demonstrated the wave nature of light and electrons, quantum interference being the manifestation of wave-particle duality. More recently, double-path interference experiments have also demonstrated the quantum-wave nature of beams of neutrons, atoms and Bose-Einstein condensates. In condensed matter systems, double-path quantum interference is observed in the d.c. superconducting quantum interference device (d.c. SQUID). Here we report a double-path quantum interference experiment involving a liquid: superfluid 3He. Using a geometry analogous to the superconducting d.c. SQUID, we control a quantum phase shift by using the rotation of the Earth, and find the classic interference pattern with periodicity determined by the 3He quantum of circulation.

Proceedings ArticleDOI
28 Oct 2001
TL;DR: Assessment of the interference caused by UWB signals via analysis and simulations finds the aggregate effect of spatially distributed UWB radios on a receiver, and theoretical BER expressions.
Abstract: Ultra-wideband (UWB) signals will encounter many interference sources, primarily from relatively narrowband (NB) systems. In addition., UWB signals will also affect a large number of NB radios; of critical importance is the potential interference with GPS, E-911, and navigation bands, as well as cellular bands. There is a rich and growing literature on UWB radios; however, issues related to interference measurements have only been partially addressed. Here, we assess the interference caused by UWB signals via analysis and simulations. Analytical results include the aggregate effect of spatially distributed UWB radios on a receiver, and theoretical BER expressions.

Journal ArticleDOI
TL;DR: In this article, a phenomenological model was introduced to find the interference pattern of a qubit's interference pattern, which allows to determine the decoherence time of the qubit.
Abstract: One may probe intrinsic coherence of a qubit by periodically sweeping its control parameter. The qubit is then excited by Landau-Zener (LZ) mechanism. The interference between multiple LZ transition leads to the unusual oscillatory dependence of the energy absorption rate on sweeping amplitude and period. This interference pattern allows to determine the decoherence time of the qubit. We introduce a simple phenomenological model describing this "interferometer", and find the form of the interference pattern.

Proceedings ArticleDOI
01 Jan 2001
TL;DR: It is shown that in case of narrowband interference (with respect to the spread spectrum bandwidth), UWB provides more effective interference suppression than DS-SS.
Abstract: In this paper we analyze the performance of ultra-wideband (UWB) communications in the presence interference. The interference is modeled as a zero mean random process with constant power spectral density over a certain bandwidth. Closed-form expressions are developed for the processing gain of a pulse position modulation UWB utilizing rectangular pulses. Simple approximations are obtained for special cases (narrowband and wideband interference). We compare the interference suppression properties of UWB and direct-sequence spread spectrum (DS-SS) under certain assumptions. It is shown that in case of narrowband interference (with respect to the spread spectrum bandwidth), UWB provides more effective interference suppression than DS-SS.

Patent
14 Aug 2001
TL;DR: In this article, a multi-mode interference (MMI) splitter divides a continuous-wave input into two branches of the interferometer, each branch has a semiconductor optical amplifier (SOA).
Abstract: Optical logic gates are constructed from Mach-Zehnder interferometer (MZI) optical circuits. A multi-mode interference (MMI) splitter divides a continuous-wave input into two branches of the interferometer. Each branch has a semiconductor optical amplifier (SOA). When a logic input having a logic-high power level is applied to one of the SOA's, cross-phase modulation occurs in the SOA. The phase shift increases through the SOA. The branch coupled to the logic input has a relative phase shift of π compared with the other branch. When two branches with the π phase difference are combined, destructive interference occurs, producing a logic low. An MMI combiner or an equivalent phase shifter is used to combine the two branches. The MMI splitter adds a phase shift of π/2 to the upper branch but not to the lower branch, while the MMI combiner also adds π/2 shifts.

Patent
13 Dec 2001
TL;DR: In this article, a method for code assignment in a spread-spectrum wireless communication system incorporating a Large Area Synchronized-Code Division Multiple Access (LAS-CDMA) protocol is presented.
Abstract: Method and apparatus for code assignments in a spread-spectrum wireless communication system incorporating a Large Area Synchronized-Code Division Multiple Access (LAS-CDMA) protocol. The method determines a set of LS codes based on an interference free window size. An arborescence structure provides the correspondence between the interference free window size and the set of LS codes. Subsets of the LS codes are formed having null cross-correlation within the interference free window. The subsets are assigned to neighboring cells in the system to reduce interference between neighbors. In one embodiment, a controller determines the subsets and makes the assignments to cells within the system.

Patent
19 Apr 2001
TL;DR: In this article, a reduced hopping sequence (RHS) scheme is proposed to reduce the number of channels being accessed by the master unit of a frequency hopping system by sending a message to one or more slave units informing them of which channels will be removed from the hopping sequence due to potential interference problems.
Abstract: A frequency hopping system such as a Bluetooth system ( 300 ) can reduce the number of RF channels it hops during a normal hopping sequence cycle providing for a Reduced Hopping Sequence (RHS). A communication unit operating in the system such as the Bluetooth master unit ( 302 ) determines if any of the RF channels has interference. If any of the channels has interference, the Bluetooth master sends a message to one or more slave units ( 304, 306 ) informing them of which channels will be removed from the hopping sequence due to potential interference problems. The units will then use the new RHS for their transmissions, thus avoiding the interference problems (e.g., both avoiding interference in the system's receivers and avoiding creating interference on frequencies that are already occupied by other neighboring systems).

Journal ArticleDOI
TL;DR: It is demonstrated that in multiple beam interference the decoherence from photon scattering cannot only lead to a decrease but, under certain conditions, also to an increase of the Michelson fringe contrast.
Abstract: We have scattered photons from an interfering path of a multiple beam Ramsey interference experiment realized with a cesium atomic beam. It is demonstrated that in multiple beam interference the decoherence from photon scattering cannot only lead to a decrease but, under certain conditions, also to an increase of the Michelson fringe contrast. In all cases, the atomic quantum state loses information with photon scattering, as ``which-path'' information is carried away by the photon field. We outline an approach to quantify this which-path information from observed fringe signals, which allows for an appropriate measure of decoherence in multiple path interference.

Proceedings ArticleDOI
06 May 2001
TL;DR: Results here show that low power UWB systems operating at the same levels as unintended radiators can comfortably coexist with conventional users of the radio spectrum without significant impact on the performance of those radio services.
Abstract: The noise floor rise in a generic receiver as a basis for the determination of interference levels to a victim receiver is applied to assess interference to systems that are designed to operate in multipath fading environments. The interference levels might be over estimated by as much a 20 dB if fading is not properly taken into account. The impact of potentially interfering sources such as UWB emissions must be treated as an effect on the overall system reliability. Results here show that low power UWB systems operating at the same levels as unintended radiators can comfortably coexist with conventional users of the radio spectrum without significant impact on the performance of those radio services.