2,618 research outputs found
Exact quantum query complexity of
In the exact quantum query model a successful algorithm must always output
the correct function value. We investigate the function that is true if exactly
or of the input bits given by an oracle are 1. We find an optimal
algorithm (for some cases), and a nontrivial general lower and upper bound on
the minimum number of queries to the black box.Comment: 19 pages, fixed some typos and constraint
More is Less: Perfectly Secure Oblivious Algorithms in the Multi-Server Setting
The problem of Oblivious RAM (ORAM) has traditionally been studied in a
single-server setting, but more recently the multi-server setting has also been
considered. Yet it is still unclear whether the multi-server setting has any
inherent advantages, e.g., whether the multi-server setting can be used to
achieve stronger security goals or provably better efficiency than is possible
in the single-server case.
In this work, we construct a perfectly secure 3-server ORAM scheme that
outperforms the best known single-server scheme by a logarithmic factor. In the
process, we also show, for the first time, that there exist specific algorithms
for which multiple servers can overcome known lower bounds in the single-server
setting.Comment: 36 pages, Accepted in Asiacrypt 201
Optimizing intermittent water supply in urban pipe distribution networks
In many urban areas of the developing world, piped water is supplied only
intermittently, as valves direct water to different parts of the water
distribution system at different times. The flow is transient, and may
transition between free-surface and pressurized, resulting in complex dynamical
features with important consequences for water suppliers and users. Here, we
develop a computational model of transition, transient pipe flow in a network,
accounting for a wide variety of realistic boundary conditions. We validate the
model against several published data sets, and demonstrate its use on a real
pipe network. The model is extended to consider several optimization problems
motivated by realistic scenarios. We demonstrate how to infer water flow in a
small pipe network from a single pressure sensor, and show how to control water
inflow to minimize damaging pressure gradients
- …