1,358 research outputs found
Conservation Pricing Of Household Water Use In Public Water Systems In Georgia's Coastal Communities: A Preliminary Exploration
The purpose of this study is to explore the effect of price on residential water use in public water supply systems in Georgia's Coastal region. Particular attention is focused on measures for the elasticity of demand for residential water use inasmuch as a showing of price inelasticity may make the wider adoption of conservation pricing more palatable to small communities with concerns that raising water prices will reduce much-needed revenues.To clarify the nature and importance of the elasticity measure, consider the following simplified example. A community sells 100 units of water for 100. Suppose price is increased by 20% to 84.00. In this case, we say that demand is "elastic;" the quantity of water used by folks "stretches" relative to the change in price. With elastic demand, rising prices mean lower total revenues. Suppose, however, that with the 20% price increase, demand fell to only 90 units -- a 10% decrease. Total revenues are now $108. In this case we say demand is inelastic -- quantity doesn't really "stretch" much when prices rise. If demand is inelastic, rising prices means higher revenues.From our limited, phase one efforts in these regards, we use aggregate water pricing data from 50 public water supply systems in 28 coastal counties that participated in a survey conducted during late the period 2003-2005. We find strong evidence that, at the margin, residential water use is indeed affected by prices charged for water in this region. We also find what we regard to be reasonably compelling evidence suggesting that residential water demand is inelastic over the range of marginal prices observed in our sample. This latter finding suggests that the use of conservation pricing as a tool for water conservation may not have an adverse effect on community revenues. Indeed, it may well be the case that increasing water prices will increase, not decrease, the community's revenues from the sale of water.In moving to phase two of this work, a great more will be accomplished in terms of refinements in the nature and quality of data used; greater efforts will be placed on attempts to identify functional forms that will yield best estimates for residential water demand in the state. Our ultimate goal is to be capable of responding to the needs of Georgia communities in the coastal region for information related to how one might improve the design of a community's water rate structure, and to conservation pricing policies that will best serve their interests and the interests of the state. Working Paper Number 2005-00
Effect of Loss on Multiplexed Single-Photon Sources
An on-demand single-photon source is a key requirement for scaling many
optical quantum technologies. A promising approach to realize an on-demand
single-photon source is to multiplex an array of heralded single-photon sources
using an active optical switching network. However, the performance of
multiplexed sources is degraded by photon loss in the optical components and
the non-unit detection efficiency of the heralding detectors. We provide a
theoretical description of a general multiplexed single-photon source with
lossy components and derive expressions for the output probabilities of
single-photon emission and multi-photon contamination. We apply these
expressions to three specific multiplexing source architectures and consider
their tradeoffs in design and performance. To assess the effect of lossy
components on near- and long-term experimental goals, we simulate the
multiplexed sources when used for many-photon state generation under various
amounts of component loss. We find that with a multiplexed source composed of
switches with ~0.2-0.4 dB loss and high efficiency number-resolving detectors,
a single-photon source capable of efficiently producing 20-40 photon states
with low multi-photon contamination is possible, offering the possibility of
unlocking new classes of experiments and technologies.Comment: Journal versio
Hard limits on the postselectability of optical graph states
Coherent control of large entangled graph states enables a wide variety of
quantum information processing tasks, including error-corrected quantum
computation. The linear optical approach offers excellent control and
coherence, but today most photon sources and entangling gates---required for
the construction of large graph states---are probabilistic and rely on
postselection. In this work, we provide proofs and heuristics to aid
experimental design using postselection. We derive a fundamental limitation on
the generation of photonic qubit states using postselected entangling gates:
experiments which contain a cycle of postselected gates cannot be postselected.
Further, we analyse experiments that use photons from postselected photon pair
sources, and lower bound the number of classes of graph state entanglement that
are accessible in the non-degenerate case---graph state entanglement classes
that contain a tree are are always accessible. Numerical investigation up to
9-qubits shows that the proportion of graph states that are accessible using
postselection diminishes rapidly. We provide tables showing which classes are
accessible for a variety of up to nine qubit resource states and sources. We
also use our methods to evaluate near-term multi-photon experiments, and
provide our algorithms for doing so.Comment: Our manuscript comprises 4843 words, 6 figures, 1 table, 47
references, and a supplementary material of 1741 words, 2 figures, 1 table,
and a Mathematica code listin
Integrated Silicon Photonics for High-Speed Quantum Key Distribution
Integrated photonics offers great potential for quantum communication devices
in terms of complexity, robustness and scalability. Silicon photonics in
particular is a leading platform for quantum photonic technologies, with
further benefits of miniaturisation, cost-effective device manufacture and
compatibility with CMOS microelectronics. However, effective techniques for
high-speed modulation of quantum states in standard silicon photonic platforms
have been limited. Here we overcome this limitation and demonstrate high-speed
low-error quantum key distribution modulation with silicon photonic devices
combining slow thermo-optic DC biases and fast (10~GHz bandwidth)
carrier-depletion modulation. The ability to scale up these integrated circuits
and incorporate microelectronics opens the way to new and advanced integrated
quantum communication technologies and larger adoption of quantum-secured
communications
Experimental Bayesian Quantum Phase Estimation on a Silicon Photonic Chip
Quantum phase estimation is a fundamental subroutine in many quantum
algorithms, including Shor's factorization algorithm and quantum simulation.
However, so far results have cast doubt on its practicability for near-term,
non-fault tolerant, quantum devices. Here we report experimental results
demonstrating that this intuition need not be true. We implement a recently
proposed adaptive Bayesian approach to quantum phase estimation and use it to
simulate molecular energies on a Silicon quantum photonic device. The approach
is verified to be well suited for pre-threshold quantum processors by
investigating its superior robustness to noise and decoherence compared to the
iterative phase estimation algorithm. This shows a promising route to unlock
the power of quantum phase estimation much sooner than previously believed
Relative multiplexing for minimizing switching in linear-optical quantum computing
Many existing schemes for linear-optical quantum computing (LOQC) depend on
multiplexing (MUX), which uses dynamic routing to enable near-deterministic
gates and sources to be constructed using heralded, probabilistic primitives.
MUXing accounts for the overwhelming majority of active switching demands in
current LOQC architectures. In this manuscript, we introduce relative
multiplexing (RMUX), a general-purpose optimization which can dramatically
reduce the active switching requirements for MUX in LOQC, and thereby reduce
hardware complexity and energy consumption, as well as relaxing demands on
performance for various photonic components. We discuss the application of RMUX
to the generation of entangled states from probabilistic single-photon sources,
and argue that an order of magnitude improvement in the rate of generation of
Bell states can be achieved. In addition, we apply RMUX to the proposal for
percolation of a 3D cluster state in [PRL 115, 020502 (2015)], and we find that
RMUX allows a 2.4x increase in loss tolerance for this architecture.Comment: Published version, New Journal of Physics, Volume 19, June 201
Dispersion Relations for Bernstein Waves in a Relativistic Pair Plasma
A fully relativistic treatment of Bernstein waves in an electron-positron
pair plasma has remained too formidable a task owing to the very complex nature
of the problem. In this article, we perform contour integration of the
dielectric response function and numerically compute the dispersion curves for
a uniform, magnetized, relativistic electron-positron pair plasma. The behavior
of the dispersion solution for several cases with different plasma temperatures
is highlighted. In particular, we find two wave modes that exist only for large
wavelengths and frequencies similar to the cyclotron frequency in a moderately
relativistic pair plasma. The results presented here have important
implications for the study of those objects where a hot magnetized
electron-positron plasma plays a fundamental role in generating the observed
radiation.Comment: 8 pages, 8 figures, Accepted for publication by Phys. Rev. E with
minor change
Fast path and polarisation manipulation of telecom wavelength single photons in lithium niobate waveguide devices
We demonstrate fast polarisation and path control of photons at 1550 nm in
lithium niobate waveguide devices using the electro-optic effect. We show
heralded single photon state engineering, quantum interference, fast state
preparation of two entangled photons and feedback control of quantum
interference. These results point the way to a single platform that will enable
the integration of nonlinear single photon sources and fast reconfigurable
circuits for future photonic quantum information science and technology.Comment: 6 page
GaN directional couplers for integrated quantum photonics
Large cross-section GaN waveguides are proposed as a suitable architecture to
achieve integrated quantum photonic circuits. Directional couplers with this
geometry have been designed with aid of the beam propagation method and
fabricated using inductively coupled plasma etching. Scanning electron
microscopy inspection shows high quality facets for end coupling and a well
defined gap between rib pairs in the coupling region. Optical characterization
at 800 nm shows single-mode operation and coupling-length-dependent splitting
ratios. Two photon interference of degenerate photon pairs has been observed in
the directional coupler by measurement of the Hong-Ou-Mandel dip with 96%
visibility.Comment: 4 pages, 5 figure
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