28 research outputs found
Remote state preparation of a photonic quantum state via quantum teleportation
We demonstrate an experimental realization of remote state preparation via
the quantum teleportation algorithm, using an entangled photon pair in the
polarization degree of freedom as the quantum resource. The input state is
encoded on the path of one of the photons from the pair. The improved
experimental scheme allows us to control the preparation and teleportation of a
state over the entire Bloch sphere with a resolution of the degree of mixture
given by the coherence length of the photon pair. Both the preparation of the
input state and the implementation of the quantum gates are performed in a pair
of chained displaced Sagnac interferometers, which contribute to the overall
robustness of the setup. An average fidelity above 0.9 is obtained for the
remote state preparation process. This scheme allows for a prepared state to be
transmitted on every repetition of the experiment, thus giving an intrinsic
success probability of 1.Comment: 6 pages, 4 figures, accepted for publication in Applied Physics
B:Lasers and Optic
Noisy quantum teleportation: An experimental study on the influence of local environments
We report experimental results on the action of selected local environments
on the fidelity of the quantum teleportation protocol, taking into account
non-ideal, realistic entangled resources. Different working conditions are
theoretically identified, where a noisy protocol can be made almost insensitive
to further addition of noise. We put to test these conditions on a photonic
implementation of the quantum teleportation algorithm, where two polarization
entangled qubits act as the entangled resource and a path qubit on Alice
encodes the state to be teleported. Bob's path qubit is used to implement a
local environment, while the environment on Alice's qubit is simulated as a
weighed average of different pure states. We obtain a good agreement with the
theoretical predictions, we experimentally recreate the conditions to obtain a
noise-induced enhancement of the protocol fidelity, and we identify parameter
regions of increased insensibility to interactions with specific noisy
environments.Comment: 9 pages, 7 figures, accepted for publication in Phys. Rev.
Entanglement breaking channels and entanglement sudden death
The occurrence of entanglement sudden death in the evolution of a bipartite
system depends on both the initial state and the channel responsible for the
evolution. An extreme case is that of entanglement braking channels, which are
channels that acting on only one of the subsystems drives them to full
disentanglement regardless of the initial state. In general, one can find
certain combinations of initial states and channels acting on one or both
subsystems that can result in entanglement sudden death or not. Neither the
channel nor the initial state, but their combination, is responsible for this
effect, but their combination. In this work we show that, in all cases, when
entanglement sudden death occurs, the evolution can be mapped to that of an
effective entanglement breaking channel on a modified initial state. Our
results allow to anticipate which states will suffer entanglement sudden death
or not for a given evolution. An experiment with polarization entangled photons
demonstrates the utility of this result in a variety of cases
Mapping the Cord Blood Transcriptome of Pregnancies Affected by Early Maternal Anemia to Identify Signatures of Fetal Programming
Context Anemia during early pregnancy (EP) is common in developing countries and is associated with adverse health consequences for both mothers and children. Offspring of women with EP anemia often have low birth weight, which increases risk for cardiometabolic diseases, including type 2 diabetes (T2D), later in life. Objective We aimed to elucidate mechanisms underlying developmental programming of adult cardiometabolic disease, including epigenetic and transcriptional alterations potentially detectable in umbilical cord blood (UCB) at time of birth. Methods We leveraged global transcriptome- and accompanying epigenome-wide changes in 48 UCB from newborns of EP anemic Tanzanian mothers and 50 controls to identify differentially expressed genes (DEGs) in UCB exposed to maternal EP anemia. DEGs were assessed for association with neonatal anthropometry and cord insulin levels. These genes were further studied in expression data from human fetal pancreas and adult islets to understand their role in beta-cell development and/or function. Results The expression of 137 genes was altered in UCB of newborns exposed to maternal EP anemia. These putative signatures of fetal programming, which included the birth weight locus LCORL, were potentially mediated by epigenetic changes in 27 genes and associated with neonatal anthropometry. Among the DEGs were P2RX7, PIK3C2B, and NUMBL, which potentially influence beta-cell development. Insulin levels were lower in EP anemia-exposed UCB, supporting the notion of developmental programming of pancreatic beta-cell dysfunction and subsequently increased risk of T2D in offspring of mothers with EP anemia. Conclusions Our data provide proof-of-concept on distinct transcriptional and epigenetic changes detectable in UCB from newborns exposed to maternal EP anemia.Peer reviewe
Autonomous open-source hardware apparatus for quantum key distribution
We describe an autonomous, fully functional implementation of the BB84 quantum key distribution protocol using open source hardware microcontrollers for the synchronization, communication, key sifting and real-time key generation diagnostics. The quantum bits are prepared in the polarization of weak optical pulses generated with light emitting diodes, and detected using a sole single-photon counter and a temporally multiplexed scheme. The system generates a shared cryptographic key at a rate of 365 bps, with a raw quantum bit error rate of 2.7%. A detailed description of the peripheral electronics for control, driving and communication between stages is released as supplementary material. The device can be built using simple and reliable hardware and it is presented as an alternative for a practical realization of sophisticated, yet accessible quantum key distribution systems.
Received: 11 Novembre 2015, Accepted: 7 January 2016; Edited by: O. MartĂnez; DOI: http://dx.doi.org/10.4279/PIP.080002
Cite as: I H LĂłpez Grande, C T Schmiegelow, M A Larotonda, Papers in Physics 8, 080002 (2016
Trapped atoms in spatially-structured vector light fields
Abstract Spatially-structured laser beams, eventually carrying orbital angular momentum, affect electronic transitions of atoms and their motional states in a complex way. We present a general framework, based on the spherical tensor decomposition of the interaction Hamiltonian, for computing atomic transition matrix elements for light fields of arbitrary spatial mode and polarization structures. We study both the bare electronic matrix elements, corresponding to transitions with no coupling to the atomic center-of-mass motion, as well as the matrix elements describing the coupling to the quantized atomic motion in the resolved side-band regime. We calculate the spatial dependence of electronic and motional matrix elements for tightly focused Hermite–Gaussian, Laguerre–Gaussian and for radially and azimuthally polarized beams. We show that near the diffraction limit, all these beams exhibit longitudinal fields and field gradients, which strongly affect the selection rules and could be used to tailor the light-matter interaction. The presented framework is useful for describing trapped atoms or ions in spatially-structured light fields and therefore for designing new protocols and setups in quantum optics, -sensing and -information processing. We provide open code to reproduce our results or to evaluate interaction matrix elements for different transition types, beam structures and interaction geometries