2 research outputs found
Manipulating the quantum information of the radial modes of trapped ions: Linear phononics, entanglement generation, quantum state transmission and non-locality tests
We present a detailed study on the possibility of manipulating quantum
information encoded in the "radial" modes of arrays of trapped ions (i.e., in
the ions' oscillations orthogonal to the trap's main axis). In such systems,
because of the tightness of transverse confinement, the radial modes pertaining
to different ions can be addressed individually. In the first part of the paper
we show that, if local control of the radial trapping frequencies is available,
any linear optical and squeezing operation on the locally defined modes - on
single as well as on many modes - can be reproduced by manipulating the
frequencies. Then, we proceed to describe schemes apt to generate unprecedented
degrees of bipartite and multipartite continuous variable entanglement under
realistic noisy working conditions, and even restricting only to a global
control of the trapping frequencies. Furthermore, we consider the transmission
of the quantum information encoded in the radial modes along the array of ions,
and show it to be possible to a remarkable degree of accuracy, for both
finite-dimensional and continuous variable quantum states. Finally, as an
application, we show that the states which can be generated in this setting
allow for the violation of multipartite non-locality tests, by feasible
displaced parity measurements. Such a demonstration would be a first test of
quantum non-locality for "massive" degrees of freedom (i.e., for degrees of
freedom describing the motion of massive particles).Comment: 21 pages; this paper, presenting a far more extensive and detailed
analysis, completely supersedes arXiv:0708.085
Measuring measurement
Measurement connects the world of quantum phenomena to the world of classical
events. It plays both a passive role, observing quantum systems, and an active
one, preparing quantum states and controlling them. Surprisingly - in the light
of the central status of measurement in quantum mechanics - there is no general
recipe for designing a detector that measures a given observable. Compounding
this, the characterization of existing detectors is typically based on partial
calibrations or elaborate models. Thus, experimental specification (i.e.
tomography) of a detector is of fundamental and practical importance. Here, we
present the realization of quantum detector tomography: we identify the optimal
positive-operator-valued measure describing the detector, with no ancillary
assumptions. This result completes the triad, state, process, and detector
tomography, required to fully specify an experiment. We characterize an
avalanche photodiode and a photon number resolving detector capable of
detecting up to eight photons. This creates a new set of tools for accurately
detecting and preparing non-classical light.Comment: 6 pages, 4 figures,see video abstract at
http://www.quantiki.org/video_abstracts/0807244