2,745 research outputs found
Characterization of quantum dynamics using quantum error correction
Characterizing noisy quantum processes is important to quantum computation
and communication (QCC), since quantum systems are generally open. To date, all
methods of characterization of quantum dynamics (CQD), typically implemented by
quantum process tomography, are \textit{off-line}, i.e., QCC and CQD are not
concurrent, as they require distinct state preparations. Here we introduce a
method, "quantum error correction based characterization of dynamics", in which
the initial state is any element from the code space of a quantum error
correcting code that can protect the state from arbitrary errors acting on the
subsystem subjected to the unknown dynamics. The statistics of stabilizer
measurements, with possible unitary pre-processing operations, are used to
characterize the noise, while the observed syndrome can be used to correct the
noisy state. Our method requires at most configurations to
characterize arbitrary noise acting on qubits.Comment: 7 pages, 2 figures; close to the published versio
Penetrative Convection at High Rayleigh Numbers
We study penetrative convection of a fluid confined between two horizontal
plates, the temperatures of which are such that a temperature of maximum
density lies between them. The range of Rayleigh numbers studied is and the Prandtl numbers are and . An
evolution equation for the growth of the convecting region is obtained through
an integral energy balance. We identify a new non-dimensional parameter,
, which is the ratio of temperature difference between the stable and
unstable regions of the flow; larger values of denote increased
stability of the upper stable layer. We study the effects of on the
flow field using well-resolved lattice Boltzmann simulations, and show that the
characteristics of the flow depend sensitively upon it. For the range , we find that for a fixed the Nusselt number,
, increases with decreasing . We also investigate the effects of
on the vertical variation of convective heat flux and the
Brunt-V\"{a}is\"{a}l\"{a} frequency. Our results clearly indicate that in the
limit the problem reduces to that of the classical
Rayleigh-B\'enard convection.Comment: 12 pages, 19 figure
On the origin of nonclassicality in single systems
In the framework of certain general probability theories of single systems,
we identify various nonclassical features such as incompatibility, multiple
pure-state decomposability, measurement disturbance, no-cloning and the
impossibility of certain universal operations, with the non-simpliciality of
the state space. This is shown to naturally suggest an underlying simplex as an
ontological model. Contextuality turns out to be an independent nonclassical
feature, arising from the intransitivity of compatibility.Comment: Close to the published versio
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