We report the experimental reconstruction of the nonequilibrium work probability distribution in a closed quantum system, and the study of the corresponding quantum fluctuation relations. The ...experiment uses a liquid-state nuclear magnetic resonance platform that offers full control on the preparation and dynamics of the system. Our endeavors enable the characterization of the out-of-equilibrium dynamics of a quantum spin from a finite-time thermodynamics viewpoint.
Robust dynamical decoupling Souza, Alexandre M.; Álvarez, Gonzalo A.; Suter, Dieter
Philosophical transactions - Royal Society. Mathematical, Physical and engineering sciences/Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences,
10/2012, Letnik:
370, Številka:
1976
Journal Article
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Quantum computers, which process information encoded in quantum mechanical systems, hold the potential to solve some of the hardest computational problems. A substantial obstacle for the further ...development of quantum computers is the fact that the lifetime of quantum information is usually too short to allow practical computation. A promising method for increasing the lifetime, known as dynamical decoupling (DD), consists of applying a periodic series of inversion pulses to the quantum bits. In the present review, we give an overview of this technique and compare different pulse sequences proposed earlier. We show that pulse imperfections, which are always present in experimental implementations, limit the performance of DD. The loss of coherence due to the accumulation of pulse errors can even exceed the perturbation from the environment. This effect can be largely eliminated by a judicious design of pulses and sequences. The corresponding sequences are largely immune to pulse imperfections and provide an increase of the coherence time of the system by several orders of magnitude.
Heat spontaneously flows from hot to cold in standard thermodynamics. However, the latter theory presupposes the absence of initial correlations between interacting systems. We here experimentally ...demonstrate the reversal of heat flow for two quantum correlated spins-1/2, initially prepared in local thermal states at different effective temperatures, employing a Nuclear Magnetic Resonance setup. We observe a spontaneous energy flow from the cold to the hot system. This process is enabled by a trade off between correlations and entropy that we quantify with information-theoretical quantities. These results highlight the subtle interplay of quantum mechanics, thermodynamics and information theory. They further provide a mechanism to control heat on the microscale.
Dynamical decoupling is a technique that protects qubits against noise. The ability to preserve quantum coherence in the presence of noise is essential for developing quantum devices. Here, the ...Rigetti quantum computing platform was used to test different dynamical decoupling sequences
in a single qubit
. The performance of the sequences was characterized by quantum process tomography and analyzed using the quantum channels formalism. Pulse imperfections are shown here to limit the performance of dynamical decoupling on the Rigetti’s qubits. However, the performance can be improved using robust dynamical decoupling, i.e., sequences that are robust against experimental imperfections. The sequences tested here outperformed previous dynamical decoupling sequences tested in the same platform.
Soil analysis is an important information in agriculture and environmental monitoring. It is usually performed by wet chemical analysis with high cost and chemical products consumption. In the world, ...it is estimated that 1.5 billion ha is used as agricultural area. If every 5 ha 2 samples (2 depths) were collected, we would have 600 million soil samples for chemical and granulometric analysis. Considering just the analysis of organic matter (OM) by wet combustion method in the laboratory as an example, we would be utilizing about 840 thousand kg of dichromate and ammonium ferrous sulfate and 3 million L of sulfuric acid. The use of these reagents can have a huge ecological consequence if they do not have an adequate final disposal. An alternative methodology such as proximal sensing can be utilized with low environmental impact. Therefore, the objective of this study was to: i) evaluate the analytical quality of soil attributes via different traditional laboratories and sensors, ii) evaluate the prediction of the models using sensors, iii) assess the uncertainties of lime recommendation analyzed by the laboratories. We applied 96 soil samples at two depths collected in São Paulo State, Brazil. The determination of 15 soil attributes was performed by four different routine laboratories, and they were predicted by 4 sensors (400–2500 nm). Results indicate that the determination of attributes via chemical analysis with low quality led to high error in spectral models. The great predictive performances of clay, OM, cation exchange capacity (CEC), and pH enable the use of sensors in the evaluation of these attributes. Overall, the criteria for classification of analytical results showed that sand, silt, clay, pH, OM, CEC, and base saturation were the attributes that can be determined by the spectroscopy technique with high-quality outcome. The lime recommendation derived from proximal sensor analysis can be used as an efficient method, since it presented a high correlation with the laboratory result. In this sense, a hybrid laboratory analysis can be developed to optimize analysis with better quality control, which is indicated as a great opportunity in the near future.
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•Traditional laboratories have variation in soil analysis results.•Attributes can be determined by the spectroscopy technique with high-quality.•VIS-NIR-SWIR reflectance spectroscopy can complement the traditional methods.•Hybrid laboratory analysis can optimize soil analysis with better quality control.•Hybrid laboratory analysis: 20% via routine laboratory and 80% via spectroscopy.•Hybrid laboratory analysis can decrease the use of toxic reagents in soil analyzes.
The performance of metal cutting tools is drastically affected by the presence of hard coatings, which promote higher productivity and superior quality to the machined components. Nevertheless, the ...conventional properties are not capable to fully predict the behavior of the tool during the operation. The surface energy of solids is a characteristic which affects the contact interactions in sliding, i.e., adsorption, wetting and adhesion. However, one of the reasons why surface energy is often neglected in tribological studies is the lack of understanding concerned with the correlation between them, mainly for friction without lubricant. This work investigates the applicability of the surface energy as a property which can be associated with the performance of AlCrN and TiAlN coated materials.
•Characterization of surface and mechanical properties of AlCrN and TiAlN coatings.•Influence of surface energy on wear of AlCrN and TiAlN coatings.•Polar and dispersive components of surface energy play an important role in the adhesive wear.•AlCrN and TiAlN coated cutting tools have their performance drastically improved.
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