Angel Sanz

Non-axisymmetric oscillations of liquid bridges

The main characteristics of the non-axisymmetric oscillations of a liquid bridge have been considered: free frequencies, deformation modes and the influence of an outer liquid. Oscillations of this kind do not show stability changes. The Plateau technique has been used to obtain the resonant frequencies of the bridge when lateral perturbations are imposed. The results obtained are in good agreement with the theoretical ones when the influence of the outer liquid is considered. Moreover, lateral oscillations observed in experiments performed with liquid bridges in space can be explained with this model.

One-dimensional linear analysis of the compound jet

The stability of an infinitely long compound liquid column is analysed by using a one-dimensional inviscid slice model. Results obtained from this one-dimensional linear analysis are applicable to the study of compound capillary jets, which are used in the ink-jet printing technique. Stability limits and the breaking regimes of such fluid configurations are established, and, whenever possible, theoretical results are compared with experimental ones.

The crystallization of a molten sphere

Abstract The crystallization process of a molten sphere supported at the end of a rod of the same material was studied, when the heat source is slowly withdrawn. As only one solidification front exists and new material is not added to the system, the shape is not coupled to the thermal problem which simplifies the solution of the whole problem. Quasi-steady quasi-onedimensional heat transfer models are used to describe the solidification front dynamics. Theoretical and experimental results are compared, showing good agreement. Therefore, the crystallization of a sphere, with the theoretical support presented here, seems to be a good method for the determination of the receding contact angle at an advancing solidification front of any kind of crystal. The shape problem solution can be used to evaluate the thermal models developed for other heating or cooling systems. The simplified thermal model developed here for the mirror furnace could be used by an experimenter to predict both the power and the pulling rate laws required to achieve a specified growth rate profile in the sphere solidification process.

LIQUID BRIDGE BREAKAGES ABOARD SPACELAB-D1

Abstract The study of the stability of long liquid columns under microgravity was the purpose of one of the experiments carried out aboard Spacelab-D1. In this paper a preliminary analysis of this experiment, mainly concerning the different liquid column breakages, is presented, As shown in the paper, the behaviour, both static and dynamic, of long liquid bridges can be accurately predicted by using available theoretical models.

The influence of gravity on the solidification of a drop

Abstract In this paper the influence of gravity on the solidification of a drop formed at the end of a rod is analyzed. Although similar studies (but ignoring gravity effects) already exist, a theoretical analysis including gravity effects allows one to improve the experimental procedure to measure on Earth relevant properties of crystals (mainly the receding contact angle ⌖ i ) which are of importance in shaped crystal growth processes. One of the main results here obtained are the shapes of the solidified drops, which are strongly dependent on the value of ⌖ i . Therefore, fitting theoretical shapes to experimental ones is a way to perform accurate measurements of ⌖ i .

Numerical simulation of information recovery in quantum computers

Decoherence is the main problem to be solved before quantum computers can be built. To control decoherence, it is possible to use error correction methods, but these methods are themselves noisy quantum computation processes. In this work, we study the ability of Steanes and Shors fault-tolerant recovering methods, as well as a modification of Steanes ancilla network, to correct errors in qubits. We test a way to measure correctly ancillas fidelity for these methods, and state the possibility of carrying out an effective error correction through a noisy quantum channel, even using noisy error correction methods.

ERROR THRESHOLD ESTIMATION BY MEANS OF THE [[7,1,3]] CSS QUANTUM CODE

The states needed in quantum computation are extremely affected by decoherence. Several methods have been proposed to control error spreading. They use two main tools: fault-tolerant constructions and concatenated quantum error correcting codes. In this work, we estimate the threshold conditions necessary to make a long enough quantum computation. The [[7,1,3]] CSS quantum code together with the Shor method to measure the error syndrome is used. No concatenation is included. The decoherence is introduced by means of the depolarizing channel error model, obtaining several thresholds from the numerical simulation. Regarding the maintenance of a qubit stabilized in the memory, the error probability must be smaller than 2.9 × 10-5. In order to implement a one or two-qubit encoded gate in an effective fault-tolerant way, it is possible to choose an adequate non-encoded noisy gate if the memory error probability is smaller than 1.3 × 10-5. In addition, fulfilling this last condition permits us to assume a more efficient behavior compared to the equivalent non-encoded process.

Effect of ancilla's structure on quantum error correction using the seven-qubit Calderbank-Shor-Steane code

In this work we discuss the ability of different types of ancillas to control the decoherence of a qubit interacting with an environment. The error is introduced into the numerical simulation via a depolarizing isotropic channel. The ranges of values considered are 10{sup -4}{<=}{epsilon}{<=}10{sup -2} for memory errors and 3x10{sup -5}{<=}{gamma}/7{<=}10{sup -2} for gate errors. After the correction we calculate the fidelity as a quality criterion for the qubit recovered. We observe that a recovery method with a three-qubit ancilla provides reasonably good results bearing in mind its economy. If we want to go further, we have to use fault tolerant ancillas with a high degree of parallelism, even if this condition implies introducing additional ancilla verification qubits.