64 research outputs found
First Things First: What Do Students Really Know About the First Amendment?
Hight school students (grades 9-12) lack knowledge of and appreciation for the U.S. Constitution, especially First Amendment rights, according to numerous surveys (First Amendment Center [FAC], 2004, 2005; Knight Foundation, 2005; National Center for Education Statistics [NCES], 1999). A review of literature about this problem reveals consistently low test scores, attempts to explain the causes of these scores, and current programs meant to raise them. However, very little research relates to specific studies of the reasons why these scores are low. Do students simply not car? Do they not remember details about these rights? The purpose of this study was to begin to identify common causes for these scores, which will help to elicit further studies leading to solutions. Over 50 students were asked about these findings on questionnaires, and 17 students were interviewed in 4 focus groups. The most common explanation for the low national survey scores were a lack of detailed knowledge about the First Amendment and a lack of concern because their rights are not threatened. The findings also indicated that classroom solutions such as simulations that deprive students of their rights and discussion of real-world situations might help spark student interest in First Amendment studies
Concrete resource analysis of the quantum linear system algorithm used to compute the electromagnetic scattering cross section of a 2D target
We provide a detailed estimate for the logical resource requirements of the
quantum linear system algorithm (QLSA) [Phys. Rev. Lett. 103, 150502 (2009)]
including the recently described elaborations [Phys. Rev. Lett. 110, 250504
(2013)]. Our resource estimates are based on the standard quantum-circuit model
of quantum computation; they comprise circuit width, circuit depth, the number
of qubits and ancilla qubits employed, and the overall number of elementary
quantum gate operations as well as more specific gate counts for each
elementary fault-tolerant gate from the standard set {X, Y, Z, H, S, T, CNOT}.
To perform these estimates, we used an approach that combines manual analysis
with automated estimates generated via the Quipper quantum programming language
and compiler. Our estimates pertain to the example problem size N=332,020,680
beyond which, according to a crude big-O complexity comparison, QLSA is
expected to run faster than the best known classical linear-system solving
algorithm. For this problem size, a desired calculation accuracy 0.01 requires
an approximate circuit width 340 and circuit depth of order if oracle
costs are excluded, and a circuit width and depth of order and
, respectively, if oracle costs are included, indicating that the
commonly ignored oracle resources are considerable. In addition to providing
detailed logical resource estimates, it is also the purpose of this paper to
demonstrate explicitly how these impressively large numbers arise with an
actual circuit implementation of a quantum algorithm. While our estimates may
prove to be conservative as more efficient advanced quantum-computation
techniques are developed, they nevertheless provide a valid baseline for
research targeting a reduction of the resource requirements, implying that a
reduction by many orders of magnitude is necessary for the algorithm to become
practical.Comment: 37 pages, 40 figure
Technology Trends for Mixed QKD/WDM Transmission up to 80 km
We give a survey of some of the recent progress made in deploying quantum and
classical communications over a shared fiber, focusing in particular on results
obtained using continuous-variable QKD.Comment: OFC 2020, 3 pages, 2 Figure
Bragg reflection waveguide as a source of wavelength-multiplexed polarization-entangled photon pairs
We put forward a new highly efficient source of paired photons entangled in
polarization with an ultra-large bandwidth. The photons are generated by means
of a conveniently designed spontaneous parametric down-conversion process in a
semiconductor type-II Bragg reflection waveguide. The proposed scheme aims at
being a key element of an integrated source of polarization-entangled photon
pairs highly suitable for its use in a multi-user quantum-key-distribution
system
Metropolitan all-pass and inter-city quantum communication network
We have demonstrated a metropolitan all-pass quantum communication network in
field fiber for four nodes. Any two nodes of them can be connected in the
network to perform quantum key distribution (QKD). An optical switching module
is presented that enables arbitrary 2-connectivity among output ports.
Integrated QKD terminals are worked out, which can operate either as a
transmitter, a receiver, or even both at the same time. Furthermore, an
additional link in another city of 60 km fiber (up to 130 km) is seamless
integrated into this network based on a trusted relay architecture. On all the
links, we have implemented protocol of decoy state scheme. All of necessary
electrical hardware, synchronization, feedback control, network software,
execution of QKD protocols are made by tailored designing, which allow a
completely automatical and stable running. Our system has been put into
operation in Hefei in August 2009, and publicly demonstrated during an
evaluation conference on quantum network organized by the Chinese Academy of
Sciences on August 29, 2009. Real-time voice telephone with one-time pad
encoding between any two of the five nodes (four all-pass nodes plus one
additional node through relay) is successfully established in the network
within 60km.Comment: 9 pages, 2 figures, 2 table
Quantum key distribution and 1 Gbit/s data encryption over a single fibre
We perform quantum key distribution (QKD) in the presence of 4 classical
channels in a C-band dense wavelength division multiplexing (DWDM)
configuration using a commercial QKD system. The classical channels are used
for key distillation and 1 Gbps encrypted communication, rendering the entire
system independent from any other communication channel than a single dedicated
fibre. We successfully distil secret keys over fibre spans of up to 50 km. The
separation between quantum channel and nearest classical channel is only 200
GHz, while the classical channels are all separated by 100 GHz. In addition to
that we discuss possible improvements and alternative configurations, for
instance whether it is advantageous to choose the quantum channel at 1310 nm or
to opt for a pure C-band configuration.Comment: 9 pages, 7 figure
Quantum entanglement distribution with 810 nm photons through active telecommunication fibers
We demonstrate the distribution of polarization-entangled photons for the
purpose of quantum key distribution (QKD) along active telecom fibers.
Entangled photon pairs of 810 nm wavelength generated by a Sagnac
interferometer source were coupled into standard telecom single mode fibers.
The fibers were either dark or carrying a standardized 1550 nm ethernet signals
(1000BASE-ZX) with a nominal speed of 1 GBps from regular media converter
devices, without any requirements on the optical power or spectrum transmitted.
Our system demonstrates a QKD network covering 6 km in distance with a central
service provider for classical and quantum data
Feasibility of quantum key distribution through dense wavelength division multiplexing network
In this paper, we study the feasibility of conducting quantum key
distribution (QKD) together with classical communication through the same
optical fiber by employing dense-wavelength-division-multiplexing (DWDM)
technology at telecom wavelength. The impact of the classical channels to the
quantum channel has been investigated for both QKD based on single photon
detection and QKD based on homodyne detection. Our studies show that the latter
can tolerate a much higher level of contamination from the classical channels
than the former. This is because the local oscillator used in the homodyne
detector acts as a "mode selector" which can suppress noise photons
effectively. We have performed simulations based on both the decoy BB84 QKD
protocol and the Gaussian modulated coherent state (GMCS) QKD protocol. While
the former cannot tolerate even one classical channel (with a power of 0dBm),
the latter can be multiplexed with 38 classical channels (0dBm power each
channel) and still has a secure distance around 10km. Preliminary experiment
has been conducted based on a 100MHz bandwidth homodyne detector.Comment: 18 pages, 5 figure
Ultra-high bandwidth quantum secured data transmission
Quantum key distribution (QKD) provides an attractive means for securing communications in optical fibre networks. However, deployment of the technology has been hampered by the frequent need for dedicated dark fibres to segregate the very weak quantum signals from conventional traffic. Up until now the coexistence of QKD with data has been limited to bandwidths that are orders of magnitude below those commonly employed in fibre optic communication networks. Using an optimised wavelength divisional multiplexing scheme, we transport QKD and the prevalent 100 Gb/s data format in the forward direction over the same fibre for the first time. We show a full quantum encryption system operating with a bandwidth of 200 Gb/s over a 100 km fibre. Exploring the ultimate limits of the technology by experimental measurements of the Raman noise, we demonstrate it is feasible to combine QKD with 10 Tb/s of data over a 50 km link. These results suggest it will be possible to integrate QKD and other quantum photonic technologies into high bandwidth data communication infrastructures, thereby allowing their widespread deployment
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