Blueprint for fault-tolerant quantum computation with Rydberg atoms

We present a blueprint for building a fault-tolerant universal quantum computer with Rydberg atoms. Our scheme, which is based on the surface code, uses individually addressable, optically trapped atoms as qubits and exploits electromagnetically induced transparency to perform the multiqubit gates required for error correction and computation. We discuss the advantages and challenges of using Rydberg atoms to build such a quantum computer, and we perform error correction simulations to obtain an error threshold for our scheme. Our findings suggest that Rydberg atoms are a promising candidate for quantum computation, but gate fidelities need to improve before fault-tolerant universal quantum computation can be achieved

BRESEX: On board supervision, basic architecture and preliminary aspects for payload and space shuttle interface

Data relative to the on board supervision subsystem are presented which were considered in a conference between INPE and NASA personnel, with the purpose of initiating a joint effort leading to the implementation of the Brazilian remote sensing experiment - (BRESEX). The BRESEX should consist, basically, of a multispectral camera for Earth observation, to be tested in a future space shuttle flight

Multiaxial Mechanical Characterization of Interpenetrating Polymer Network Reinforced Acrylic Elastomer

The acrylic elastomer membrane VHB 4910 is a material widely used for applications as Dielectric Elastomer Actuators DEA. For suitable actuation performance however, it is necessary to pre-strain the very compliant membrane. This reduces the lifetime of DEA due to early failure of the tensioned membrane. Interpenetrating Polymer Network Reinforced Acrylic Elastomers (IPN) are produced by introducing a curable additive into the pre-strained acrylic elastomer membrane. While curing at elevated temperature, the additive forms a second polymeric network that supports part of the pre-strain in the acrylic membrane. This leads to a free standing material that combines the actuation performance of pre-strained VHB 4910 with an excellent long-term reliability. This work presents a detailed mechanical characterization of acrylic IPN membranes. To reduce the experimental effort required to characterize the nonlinear elastic behavior, we developed a unique specimen design that enables the assessment of uni- and biaxial stress states within one experiment. Slight changes in the material composition of IPN-membranes lead to substantial variations in their mechanical properties. The extraction of material behavior in different kinematic states within a single sample thus reduces the uncertainty on the determination of constitutive models. An extensive experimental campaign was carried out involving uniaxial and equibiaxial tension and relaxation. Image based local deformation measurements and iterative finite element calculations were applied to derive constitutive model parameters that describe the mechanical response in a wide range of planar strain and strain rat

Body center of mass trajectory and mechanical energy using inertial sensors: a feasible stride?

Background: The description of the three-dimensional (3D) trajectory of the body center of mass (BCoM) provides useful insights on the mechanics of locomotion. The BCoM trajectory can be estimated from ground reaction forces, recorded by force platforms (GRF, gold standard), or from marker trajectories recorded by stereophotogrammetric systems (MKR). However, both instruments do not allow for monitoring locomotion in the real-life environment. In this perspective, magneto-inertial measurement units (MIMUs) are particularly attractive being wearable, thus enabling to collect movement data out of the laboratory. Research questions: To investigate the feasibility and accuracy of a recent marketed full-body MIMU-based method for the estimation of the 3D BCoM trajectory and energetics during walking. Methods: Twelve subjects walked at self-selected and slow speed along a 12 m long walkway. GRF and MKR were acquired using three force platforms and a stereophotogrammetric system. MIMU data were collected using a full-body MIMU-based motion capture system (Xsens MTw Awinda). The 3D BCoM trajectory, external mechanical work and energy recovery were extracted from the data acquired by the three measurement systems, using state-of-the-art methods. The accuracy of both MKR- and MIMU-based estimates compared with GRF was assessed for the BCoM trajectory (maximum, minimum, range, and RMSD), as well as for mechanical work and energy recovery. Results: A total number of 108 strides were analyzed. MIMU-based BCoM trajectory displayed larger errors in comparison with GRF (and MKR) for the trajectory ranges: 89 ± 47(93 ± 44)% in antero-posterior, 46 ± 25(40 ± 79)% medio-lateral and -13 ± 23(-5 ± 25)% vertical directions, leading to a 3D RMSD of 17 ± 5(12 ± 5) mm (mean ± SD). These discrepancies largely affected the estimation of both mechanical work and energy recovery (+115 ± 85% and -28 ± 21%, respectively). Significance: Preliminary findings highlighted that the tested MIMU-based method for BCoM trajectory estimation still lacks accuracy and that the quantification of energetics in real-life situations remains an open challenge

Controllable Wave Propagation of Hybrid Dispersive Medium with LC High-Pass Network

ISSN:0277-786

Deterministic single-atom excitation via adiabatic passage and Rydberg blockade

We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number \textit{N} of the atoms in the traps. Our method overcomes the problem of the $\sqrt {N}$ dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitation in the ensembles with unknown \textit{N}, and can be applied for single-atom loading of dipole traps and optical lattices.Comment: 6 pages, 5 figures. Version 5 is expanded and submitted to PRA. Typo in Fig.4 corrected in Version 2. Version 3 and 4 are duplicates of V

Coherent imaging of extended objects

When used with coherent light, optical imaging systems, even diffraction-limited, are inherently unable to reproduce both the amplitude and the phase of a two-dimensional field distribution because their impulse response function varies slowly from point to point (a property known as non-isoplanatism). For sufficiently small objects, this usually results in a phase distortion and has no impact on the measured intensity. Here, we show that the intensity distribution can also be dramatically distorted when objects of large extension or of special shapes are imaged. We illustrate the problem using two simple examples: the pinhole camera and the aberration-free thin lens. The effects predicted by our theorical analysis are also confirmed by experimental observations.Comment: 10 pages, 9 figures, submitted to Optics Communication

Sublattice addressing and spin-dependent motion of atoms in a double-well lattice

We load atoms into every site of an optical lattice and selectively spin flip atoms in a sublattice consisting of every other site. These selected atoms are separated from their unselected neighbors by less than an optical wavelength. We also show spin-dependent transport, where atomic wave packets are coherently separated into adjacent sites according to their internal state. These tools should be useful for quantum information processing and quantum simulation of lattice models with neutral atoms