17,543 research outputs found
On-chip quantum tomography of mechanical nano-scale oscillators with guided Rydberg atoms
Nano-mechanical oscillators as well as Rydberg-atomic waveguides hosted on
micro-fabricated chip surfaces hold promise to become pillars of future quantum
technologies. In a hybrid platform with both, we show that beams of Rydberg
atoms in waveguides can quantum-coherently interrogate and manipulate
nanomechanical elements, allowing full quantum state tomography. Central to the
tomography are quantum non-demolition measurements using the Rydberg atoms as
probes. Quantum coherent displacement of the oscillator is also made possible,
by driving the atoms with external fields while they interact with the
oscillator. We numerically demonstrate the feasibility of this fully integrated
on-chip control and read-out suite for quantum nano-mechanics, taking into
account noise and error sources.Comment: 11 pages, 5 figures, 1 tabl
Enabling science with Gaia observations of naked-eye stars
ESA's Gaia space astrometry mission is performing an all-sky survey of
stellar objects. At the beginning of the nominal mission in July 2014, an
operation scheme was adopted that enabled Gaia to routinely acquire
observations of all stars brighter than the original limit of G~6, i.e. the
naked-eye stars. Here, we describe the current status and extent of those
observations and their on-ground processing. We present an overview of the data
products generated for G<6 stars and the potential scientific applications.
Finally, we discuss how the Gaia survey could be enhanced by further exploiting
the techniques we developed.Comment: 16 pages, 8 figures. Submitted for the proceedings of the 2016 SPIE
Astronomical Instrumentation and Telescopes conference (SPIE 9904
Universal resources for approximate and stochastic measurement-based quantum computation
We investigate which quantum states can serve as universal resources for
approximate and stochastic measurement-based quantum computation, in the sense
that any quantum state can be generated from a given resource by means of
single-qubit (local) operations assisted by classical communication. More
precisely, we consider the approximate and stochastic generation of states,
resulting e.g. from a restriction to finite measurement settings or from
possible imperfections in the resources or local operations. We show that
entanglement-based criteria for universality obtained for the exact,
deterministic case can be lifted to the much more general approximate,
stochastic case, moving from the idealized situation considered in previous
works, to the practically relevant context of non-perfect state preparation. We
find that any entanglement measure fulfilling some basic requirements needs to
reach its maximum value on some element of an approximate, stochastic universal
family of resource states, as the resource size grows. This allows us to rule
out various families of states as being approximate, stochastic universal. We
provide examples of resources that are efficient approximate universal, but not
exact deterministic universal. We also study the robustness of universal
resources for measurement-based quantum computation under realistic assumptions
about the (imperfect) generation and manipulation of entangled states, giving
an explicit expression for the impact that errors made in the preparation of
the resource have on the possibility to use it for universal approximate and
stochastic state preparation. Finally, we discuss the relation between our
entanglement-based criteria and recent results regarding the uselessness of
states with a high degree of geometric entanglement as universal resources.Comment: 17 pages; abstract shortened with respect to the published version to
respect the arXiv limit of 1,920 character
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