2,668 research outputs found
Memorable And Secure: How Do You Choose Your PIN?
Managing all your PINs is difficult. Banks acknowledge this by allowing and facilitating PIN
changes. However, choosing secure PINs is a difficult task for humans as they are incapable of
consciously generating randomness. This leads to certain PINs being chosen more frequently
than others, which in turn increases the danger of someone else guessing correctly. We
investigate different methods of supporting PIN changes and report on an evaluation of these
methods in a study with 152 participants. Our contribution is twofold: We introduce an
alternative to system-generated random PINs, which considers people’s preferred
memorisation strategy, and, secondly, we provide indication that presenting guidance on how
to avoid insecure PINs does indeed nudge people towards more secure PIN choices when they
are in the process of changing their PINs
Correlation functions of the One-Dimensional Random Field Ising Model at Zero Temperature
We consider the one-dimensional random field Ising model, where the spin-spin
coupling, , is ferromagnetic and the external field is chosen to be
with probability and with probability . At zero temperature, we
calculate an exact expression for the correlation length of the quenched
average of the correlation function in the case that is not an integer. The
result is a discontinuous function of . When , we also
place a bound on the correlation length of the quenched average of the
correlation function .Comment: 12 pages (Plain TeX with one PostScript figure appended at end), MIT
CTP #220
Intra-Ethnic Diversity in Hispanic Child Mortality, 1890-1910
The recent demography of the Hispanic population of the United States has received considerable attention, but historical perspective is more elusive partly due to data limitations. A nationally representative sample of the Hispanic population of the United States, based on the manuscripts of the 1910 census, now exists that includes 71,500 Hispanic-origin persons plus another 24,000 of their non-Hispanic neighbors. We estimate childhood mortality for 1890 to 1910, using indirect demographic methods of estimation and find infant and child mortality in the Hispanic population that was higher than for the non-Hispanic whites but slightly lower than for nonwhite, non-Hispanics (mostly African Americans). Hispanic rural, farm populations in California, Texas, and Arizona did the best, though still experiencing high mortality. The usual advantage of rural residence at the turn of the century holds outside of New Mexico and Florida.
Convergence theorems for quantum annealing
We prove several theorems to give sufficient conditions for convergence of
quantum annealing, which is a protocol to solve generic optimization problems
by quantum dynamics. In particular the property of strong ergodicity is proved
for the path-integral Monte Carlo implementation of quantum annealing for the
transverse Ising model under a power decay of the transverse field. This result
is to be compared with the much slower inverse-log decay of temperature in the
conventional simulated annealing. Similar results are proved for the Green's
function Monte Carlo approach. Optimization problems in continuous space of
particle configurations are also discussed.Comment: 19 page
Approximating Fractional Time Quantum Evolution
An algorithm is presented for approximating arbitrary powers of a black box
unitary operation, , where is a real number, and
is a black box implementing an unknown unitary. The complexity of
this algorithm is calculated in terms of the number of calls to the black box,
the errors in the approximation, and a certain `gap' parameter. For general
and large , one should apply a total of times followed by our procedure for approximating the fractional
power . An example is also given where for
large integers this method is more efficient than direct application of
copies of . Further applications and related algorithms are also
discussed.Comment: 13 pages, 2 figure
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