514 research outputs found
Cross-verification of independent quantum devices
Quantum computers are on the brink of surpassing the capabilities of even the
most powerful classical computers. This naturally raises the question of how
one can trust the results of a quantum computer when they cannot be compared to
classical simulation. Here we present a verification technique that exploits
the principles of measurement-based quantum computation to link quantum
circuits of different input size, depth, and structure. Our approach enables
consistency checks of quantum computations within a device, as well as between
independent devices. We showcase our protocol by applying it to five
state-of-the-art quantum processors, based on four distinct physical
architectures: nuclear magnetic resonance, superconducting circuits, trapped
ions, and photonics, with up to 6 qubits and 200 distinct circuits
Entanglement Transfer via XXZ Heisenberg chain with DM Interaction
The role of spin-orbit interaction, arises from the Dzyaloshinski-Moriya
anisotropic antisymmetric interaction, on the entanglement transfer via an
antiferromagnetic XXZ Heisenberg chain is investigated. From symmetrical point
of view, the XXZ Hamiltonian with Dzyaloshinski-Moriya interaction can be
replaced by a modified XXZ Hamiltonian which is defined by a new exchange
coupling constant and rotated Pauli operators. The modified coupling constant
and the angle of rotations are depend on the strength of Dzyaloshinski-Moriya
interaction. In this paper we study the dynamical behavior of the entanglement
propagation through a system which is consist of a pair of maximally entangled
spins coupled to one end of the chain. The calculations are performed for the
ground state and the thermal state of the chain, separately. In both cases the
presence of this anisotropic interaction make our channel more efficient, such
that the speed of transmission and the amount of the entanglement are improved
as this interaction is switched on. We show that for large values of the
strength of this interaction a large family of XXZ chains becomes efficient
quantum channels, for whole values of an isotropy parameter in the region .Comment: 21 pages, 9 figure
State space modelling and data analysis exercises in LISA Pathfinder
LISA Pathfinder is a mission planned by the European Space Agency to test the
key technologies that will allow the detection of gravitational waves in space.
The instrument on-board, the LISA Technology package, will undergo an
exhaustive campaign of calibrations and noise characterisation campaigns in
order to fully describe the noise model. Data analysis plays an important role
in the mission and for that reason the data analysis team has been developing a
toolbox which contains all the functionalities required during operations. In
this contribution we give an overview of recent activities, focusing on the
improvements in the modelling of the instrument and in the data analysis
campaigns performed both with real and simulated data.Comment: Plenary talk presented at the 9th International LISA Symposium, 21-25
May 2012, Pari
Beyond the required LISA free-fall performance: new LISA pathfinder results down to 20ââÎŒHz
In the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20ââÎŒHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05)ââfmâs^{-2}/sqrt[Hz] above 2 mHz and (6±1)Ă10ââfmâs^{-2}/sqrt[Hz] at 20ââÎŒHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency
In-flight thermal experiments for LISA pathfinder: simulating temperature noise at the inertial sensors
Thermal Diagnostics experiments to be carried out on board LISA Pathfinder (LPF) will yield a detailed characterisation of how temperature fluctuations affect the LTP (LISA Technology Package) instrument performance, a crucial information for future space based gravitational wave detectors as the proposed eLISA. Amongst them, the study of temperature gradient fluctuations around the test masses of the Inertial Sensors will provide as well information regarding the contribution of the Brownian noise, which is expected to limit the LTP sensitivity at frequencies close to 1 mHz during some LTP experiments. In this paper we report on how these kind of Thermal Diagnostics experiments were simulated in the last LPF Simulation Campaign (November, 2013) involving all the LPF Data Analysis team and using an end-to-end simulator of the whole spacecraft. Such simulation campaign was conducted under the framework of the preparation for LPF operations
Free-flight experiments in LISA Pathfinder
The LISA Pathfinder mission will demonstrate the technology of drag-free test
masses for use as inertial references in future space-based gravitational wave
detectors. To accomplish this, the Pathfinder spacecraft will perform drag-free
flight about a test mass while measuring the acceleration of this primary test
mass relative to a second reference test mass. Because the reference test mass
is contained within the same spacecraft, it is necessary to apply forces on it
to maintain its position and attitude relative to the spacecraft. These forces
are a potential source of acceleration noise in the LISA Pathfinder system that
are not present in the full LISA configuration. While LISA Pathfinder has been
designed to meet it's primary mission requirements in the presence of this
noise, recent estimates suggest that the on-orbit performance may be limited by
this `suspension noise'. The drift-mode or free-flight experiments provide an
opportunity to mitigate this noise source and further characterize the
underlying disturbances that are of interest to the designers of LISA-like
instruments. This article provides a high-level overview of these experiments
and the methods under development to analyze the resulting data.Comment: 13 pages, 5 figures. Accepted to Journal Of Physics, Conference
Series. Presented at 10th International LISA Symposium, May 2014,
Gainesville, FL, US
Sub-femto-g free fall for space-based gravitational wave observatories: LISA pathfinder results
We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2 ± 0.1 fm sâ2/âHz or (0.54 ± 0.01) Ă 10â15 g/âHz, with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8 ± 0.3) fm/âHz, about 2 orders of magnitude better than requirements. At f †0.5 mHz we observe a low-frequency tail that stays below 12 fm sâ2/âHz down to 0.1 mHz. This performance would allow for a space-based gravitational wave
observatory with a sensitivity close to what was originally foreseen for LISA
The LISA pathfinder mission
ISA Pathfinder (LPF), the second of the European Space Agency's Small Missions for Advanced Research in Technology (SMART), is a dedicated technology validation mission for future spaceborne gravitational wave detectors, such as the proposed eLISA mission. LISA Pathfinder, and its scientific payload - the LISA Technology Package - will test, in flight, the critical technologies required for low frequency gravitational wave detection: it will put two test masses in a near-perfect gravitational free-fall and control and measure their motion with unprecedented accuracy. This is achieved through technology comprising inertial sensors, high precision laser metrology, drag-free control and an ultra-precise micro-Newton propulsion system. LISA Pathfinder is due to be launched in mid-2015, with first results on the performance of the system being available 6 months thereafter.
The paper introduces the LISA Pathfinder mission, followed by an explanation of the physical principles of measurement concept and associated hardware. We then provide a detailed discussion of the LISA Technology Package, including both the inertial sensor and interferometric readout. As we approach the launch of the LISA Pathfinder, the focus of the development is shifting towards the science operations and data analysis - this is described in the final section of the paper
Cytogenetic analysis of three sea catfish species (Teleostei, Siluriformes, Ariidae) with the first report of Ag-NOR in this fish family
Despite their ecological and economical importance, fishes of the family Ariidae are still genetically and cytogenetically poorly studied. Among the 133 known species of ariids, only eight have been karyotyped. Cytogenetic analyses performed on Genidens barbus and Sciades herzbergii revealed that both species have 2n = 56 chromosomes and Cathorops aff. mapale has 2n = 52 chromosomes: Genidens barbus has 10 Metacentrics (M), 14 Submetacentrics (SM), 26 Subtelocentrics (ST), and 6 Acrocentrics (A), Sciades herzbergii has 14M, 20SM, 18ST and 4A, whereas Cathorops aff. mapale has 14M, 20SM, and 18ST. The nucleolus organizer regions (NORs) were found in a single chromosome pair on the short arm of a large-sized ST pair in Genidens barbus and on the short arm of a middle-size SM pair in Cathorops aff. mapale. Multiple NORs on the short arms of two large-sized ST pairs were found in Sciades herzbergii. The occurrence of diploid numbers ranging from 2n = 52 through 56 chromosomes and the presence of different karyotypic compositions, besides the number and position of NORs suggest that several numeric and structural chromosome rearrangements were fixed during the evolutionary history of this fish family
A noise simulator for eLISA: migrating LISA pathfinder knowledge to the eLISA mission
We present a new technical simulator for the eLISA mission, based on state space modeling techniques and developed in MATLAB. This simulator computes the coordinate and velocity over time of each body involved in the constellation, i.e. the spacecraft and its test masses, taking into account the different disturbances and actuations. This allows studying the contribution of instrumental noises and system imperfections on the residual acceleration applied on the TMs, the latter reflecting the performance of the achieved free-fall along the sensitive axis. A preliminary version of the results is presented
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