28,442 research outputs found
Explicit tracking of uncertainty increases the power of quantitative rule-of-thumb reasoning in cell biology
"Back-of-the-envelope" or "rule-of-thumb" calculations involving rough
estimates of quantities play a central scientific role in developing intuition
about the structure and behaviour of physical systems, for example in so-called
`Fermi problems' in the physical sciences. Such calculations can be used to
powerfully and quantitatively reason about biological systems, particularly at
the interface between physics and biology. However, substantial uncertainties
are often associated with values in cell biology, and performing calculations
without taking this uncertainty into account may limit the extent to which
results can be interpreted for a given problem. We present a means to
facilitate such calculations where uncertainties are explicitly tracked through
the line of reasoning, and introduce a `probabilistic calculator' called
Caladis, a web tool freely available at www.caladis.org, designed to perform
this tracking. This approach allows users to perform more statistically robust
calculations in cell biology despite having uncertain values, and to identify
which quantities need to be measured more precisely in order to make confident
statements, facilitating efficient experimental design. We illustrate the use
of our tool for tracking uncertainty in several example biological
calculations, showing that the results yield powerful and interpretable
statistics on the quantities of interest. We also demonstrate that the outcomes
of calculations may differ from point estimates when uncertainty is accurately
tracked. An integral link between Caladis and the Bionumbers repository of
biological quantities further facilitates the straightforward location,
selection, and use of a wealth of experimental data in cell biological
calculations.Comment: 8 pages, 3 figure
Optical Quantum Computation with Perpetually Coupled Spins
The possibility of using strongly and continuously interacting spins for
quantum computation has recently been discussed. Here we present a simple
optical scheme that achieves this goal while avoiding the drawbacks of earlier
proposals. We employ a third state, accessed by a classical laser field, to
create an effective barrier to information transfer. The mechanism proves to be
highly efficient both for continuous and pulsed laser modes; moreover it is
very robust, tolerating high decay rates for the excited states. The approach
is applicable to a broad range of systems, in particular dense structures such
as solid state self-assembled (e.g., molecular) devices. Importantly, there are
existing structures upon which `first step' experiments could be immediately
performed.Comment: 5 pages including 3 figures. Updated to published versio
A Search for New Physics with the BEACON Mission
The primary objective of the Beyond Einstein Advanced Coherent Optical
Network (BEACON) mission is a search for new physics beyond general relativity
by measuring the curvature of relativistic space-time around Earth. This
curvature is characterized by the Eddington parameter \gamma -- the most
fundamental relativistic gravity parameter and a direct measure for the
presence of new physical interactions. BEACON will achieve an accuracy of 1 x
10^{-9} in measuring the parameter \gamma, thereby going a factor of 30,000
beyond the present best result involving the Cassini spacecraft. Secondary
mission objectives include: (i) a direct measurement of the "frame-dragging"
and geodetic precessions in the Earth's rotational gravitomagnetic field, to
0.05% and 0.03% accuracy correspondingly, (ii) first measurement of gravity's
non-linear effects on light and corresponding 2nd order spatial metric's
effects to 0.01% accuracy. BEACON will lead to robust advances in tests of
fundamental physics -- this mission could discover a violation or extension of
general relativity and/or reveal the presence of an additional long range
interaction in physics. BEACON will provide crucial information to separate
modern scalar-tensor theories of gravity from general relativity, probe
possible ways for gravity quantization, and test modern theories of
cosmological evolution.Comment: 8 pages, 2 figures, 2 table
Quantum Computing on Lattices using Global Two-Qubit Gate
We study the computation power of lattices composed of two dimensional
systems (qubits) on which translationally invariant global two-qubit gates can
be performed. We show that if a specific set of 6 global two qubit gates can be
performed, and if the initial state of the lattice can be suitably chosen, then
a quantum computer can be efficiently simulatedComment: 9 page
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