977 research outputs found
Vulnerabilities in Quantum Key Distribution Protocols
Recently proposed quantum key distribution protocols are shown to be
vulnerable to a classic man-in-the-middle attack using entangled pairs created
by Eve. It appears that the attack could be applied to any protocol that relies
on manipulation and return of entangled qubits to create a shared key. The
protocols that are cryptanalyzed in this paper were proven secure with respect
to some eavesdropping approaches, and results reported here do not invalidate
these proofs. Rather, they suggest that quantum cryptographic protocols, like
conventional protocols, may be vulnerable to methods of attack that were not
envisaged by their designers.Comment: 6 pages, 1 figur
Genetic Algorithms for Redundancy in Interaction Testing
It is imperative for testing to determine if the components within
large-scale software systems operate functionally. Interaction testing involves
designing a suite of tests, which guarantees to detect a fault if one exists
among a small number of components interacting together. The cost of this
testing is typically modeled by the number of tests, and thus much effort has
been taken in reducing this number. Here, we incorporate redundancy into the
model, which allows for testing in non-deterministic environments. Existing
algorithms for constructing these test suites usually involve one "fast"
algorithm for generating most of the tests, and another "slower" algorithm to
"complete" the test suite. We employ a genetic algorithm that generalizes these
approaches that also incorporates redundancy by increasing the number of
algorithms chosen, which we call "stages." By increasing the number of stages,
we show that not only can the number of tests be reduced compared to existing
techniques, but the computational time in generating them is also greatly
reduced.Comment: Submitted to Genetic and Evolutionary Computation Conference 2020
(GECCO '20
Coherent and robust high-fidelity generation of a biexciton in a quantum dot by rapid adiabatic passage
A biexciton in a semiconductor quantum dot is a source of
polarization-entangled photons with high potential for implementation in
scalable systems. Several approaches for non-resonant, resonant and
quasi-resonant biexciton preparation exist, but all have their own
disadvantages, for instance low fidelity, timing jitter, incoherence or
sensitivity to experimental parameters. We demonstrate a coherent and robust
technique to generate a biexciton in an InGaAs quantum dot with a fidelity
close to one. The main concept is the application of rapid adiabatic passage to
the ground state-exciton-biexciton system. We reinforce our experimental
results with simulations which include a microscopic coupling to phonons.Comment: Main manuscript 5 pages and 4 figures, Supplementary Information 5
pages and 3 figures, accepted as a Rapid Communication in PRB. arXiv admin
note: text overlap with arXiv:1701.0130
A Survey of Binary Covering Arrays
Binary covering arrays of strength t are 0–1 matrices having the property that for each t columns and each of the possible 2[superscript t] sequences of t 0's and 1's, there exists a row having that sequence in that set of t columns. Covering arrays are an important tool in certain applications, for example, in software testing. In these applications, the number of columns of the matrix is dictated by the application, and it is desirable to have a covering array with a small number of rows. Here we survey some of what is known about the existence of binary covering arrays and methods of producing them, including both explicit constructions and search techniques
Demonstrating the decoupling regime of the electron-phonon interaction in a quantum dot using chirped optical excitation
Excitation of a semiconductor quantum dot with a chirped laser pulse allows
excitons to be created by rapid adiabatic passage. In quantum dots this process
can be greatly hindered by the coupling to phonons. Here we add a high chirp
rate to ultra-short laser pulses and use these pulses to excite a single
quantum dot. We demonstrate that we enter a regime where the exciton-phonon
coupling is effective for small pulse areas, while for higher pulse areas a
decoupling of the exciton from the phonons occurs. We thus discover a
reappearance of rapid adiabatic passage, in analogy to the predicted
reappearance of Rabi rotations at high pulse areas. The measured results are in
good agreement with theoretical calculations.Comment: Main manuscript 5 pages and 4 figures, Supplementary Information 5
pages and 3 figures, submitted to PR
Finding Bugs in Cryptographic Hash Function Implementations
Cryptographic hash functions are security-critical algorithms with many practical applications, notably in digital signatures. Developing an approach to test them can be particularly difficult, and bugs can remain unnoticed for many years. We revisit the NIST hash function competition, which was used to develop the SHA-3 standard, and apply a new testing strategy to all available reference implementations. Motivated by the cryptographic properties that a hash function should satisfy, we develop four tests. The Bit-Contribution Test checks if changes in the message affect the hash value, and the Bit-Exclusion Test checks that changes beyond the last message bit leave the hash value unchanged. We develop the Update Test to verify that messages are processed correctly in chunks, and then use combinatorial testing methods to reduce the test set size by several orders of magnitude while retaining the same fault-detection capability. Our tests detect bugs in 41 of the 86 reference implementations submitted to the SHA-3 competition, including the rediscovery of a bug in all submitted implementations of the SHA-3 finalist BLAKE. This bug remained undiscovered for seven years, and is particularly serious because it provides a simple strategy to modify the message without changing the hash value returned by the implementation. We detect these bugs using a fully-automated testing approach
The mediating effect of task presentation on collaboration and children's acquisition of scientific reasoning
There has been considerable research concerning peer interaction and the acquisition of children's scientific reasoning. This study investigated differences in collaborative activity between pairs of children working around a computer with pairs of children working with physical apparatus and related any differences to the development of children's scientific reasoning. Children aged between 9 and 10 years old (48 boys and 48 girls) were placed into either same ability or mixed ability pairs according to their individual, pre-test performance on a scientific reasoning task. These pairs then worked on either a computer version or a physical version of Inhelder and Piaget's (1958) chemical combination task. Type of presentation was found to mediate the nature and type of collaborative activity. The mixed-ability pairs working around the computer talked proportionally more about the task and management of the task; had proportionally more transactive discussions and used the record more productively than children working with the physical apparatus. Type of presentation was also found to mediated children's learning. Children in same ability pairs who worked with the physical apparatus improved significantly more than same ability pairs who worked around the computer. These findings were partially predicted from a socio-cultural theory and show the importance of tools for mediating collaborative activity and collaborative learning
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