58 research outputs found
The cost of exactly simulating quantum entanglement with classical communication
We investigate the amount of communication that must augment classical local
hidden variable models in order to simulate the behaviour of entangled quantum
systems. We consider the scenario where a bipartite measurement is given from a
set of possibilities and the goal is to obtain exactly the same correlations
that arise when the actual quantum system is measured. We show that, in the
case of a single pair of qubits in a Bell state, a constant number of bits of
communication is always sufficient--regardless of the number of measurements
under consideration. We also show that, in the case of a system of n Bell
states, a constant times 2^n bits of communication are necessary.Comment: 9 pages, LaTeX, no figure
Quantum Amplitude Amplification and Estimation
Consider a Boolean function that partitions set
between its good and bad elements, where is good if and bad
otherwise. Consider also a quantum algorithm such that is a quantum superposition of the
elements of , and let denote the probability that a good element is
produced if is measured. If we repeat the process of running ,
measuring the output, and using to check the validity of the result, we
shall expect to repeat times on the average before a solution is found.
*Amplitude amplification* is a process that allows to find a good after an
expected number of applications of and its inverse which is proportional to
, assuming algorithm makes no measurements. This is a
generalization of Grover's searching algorithm in which was restricted to
producing an equal superposition of all members of and we had a promise
that a single existed such that . Our algorithm works whether or
not the value of is known ahead of time. In case the value of is known,
we can find a good after a number of applications of and its inverse
which is proportional to even in the worst case. We show that this
quadratic speedup can also be obtained for a large family of search problems
for which good classical heuristics exist. Finally, as our main result, we
combine ideas from Grover's and Shor's quantum algorithms to perform amplitude
estimation, a process that allows to estimate the value of . We apply
amplitude estimation to the problem of *approximate counting*, in which we wish
to estimate the number of such that . We obtain optimal
quantum algorithms in a variety of settings.Comment: 32 pages, no figure
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A patient with anti-NXP2-positive dermatomyositis and syphilis
Dermatomyositis is an auto-immune inflammatory myopathy that primarily affects the skin and muscle and can be triggered by exposure to various environmental factors. We present a patient with active syphilis infection who developed dermatomyositis and discuss the significance of anti-NXP2 autoantibody positivity
A limit on nonlocality in any world in which communication complexity is not trivial
Bell proved that quantum entanglement enables two space-like separated
parties to exhibit classically impossible correlations. Even though these
correlations are stronger than anything classically achievable, they cannot be
harnessed to make instantaneous (faster than light) communication possible.
Yet, Popescu and Rohrlich have shown that even stronger correlations can be
defined, under which instantaneous communication remains impossible. This
raises the question: Why are the correlations achievable by quantum mechanics
not maximal among those that preserve causality? We give a partial answer to
this question by showing that slightly stronger correlations would result in a
world in which communication complexity becomes trivial.Comment: 13 pages, no figure
La gestion des Activités éducatives de la direction et le fonctionnement de l'école primaire
Many actors in the field of education assert that principals should pay closer attention to educational activities in order to ensure students' achievement. This paper presents a research conducted with 138 principals and 421 teachers which aimed at assessing the frequency of principals' interventions on managing educational activities in elementary schools in Quebec. In addition, this study examines the relations between principals' management of educational activities and the different aspect of the school's functioning. The results show that principals intervene more frequently in specific areas of management such as parents' involvement and the support of at-risk students rather than the supervision of teachers and students' performance. Hence, the quality of the school's functioning varies in the nature and frequency of the principal's intervention which illustrates the importance of their managerial work.Key words: management of educational activities, educational leadership, school's functioning, students' achievement
Detection of Hepatitis E virus in swine using real-time RT-PCR
The zoonotic transmtsswn potential of Hepatitis E virus (HEY) is now widely recognized. Swine represents the main animal reservoir for this virus in many countries, including Canada. In recent years, different real-time RT-PCR assays were developed and proposed as reliable and sensitive detection methods. However, the quality of extracted RNA, presence of inhibitors and RN ase contamination of the samples may impact on the detection results obtained with these molecular methods. The aim of this study was to evaluate the use of a sample process control (SPC) within a real-time RT-PCR assay for the detection ofHEV. This TaqMan multiplex assay was afterwards used to evaluate the viral load ofHEV in organs, tissues and excreta of normal pigs at slaughter. HEY RNA was detected in at least one sample from 14 out of the 43 animals tested (32.6 %). HEV was present in lymph nodes (25.6%), bladder (23.3%), liver (20.9%), bile (18.6%), feces (13.9%), tonsils (7.0%) and plasma (2.3%) but was undetected in loins
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