Perfect initialization of a quantum computer of neutral atoms in an optical lattice of large lattice constant

We propose a scheme for the initialization of a quantum computer based on neutral atoms trapped in an optical lattice with large lattice constant. Our focus is the development of a compacting scheme to prepare a perfect optical lattice of simple orthorhombic structure with unit occupancy. Compacting is accomplished by sequential application of two types of operations: a flip operator that changes the internal state of the atoms, and a shift operator that moves them along the lattice principal axis. We propose physical mechanisms for realization of these operations and we study the effects of motional heating of the atoms. We carry out an analysis of the complexity of the compacting scheme and show that it scales linearly with the number of lattice sites per row of the lattice, thus showing good scaling behavior with the size of the quantum computer.Comment: 18 page

Lombar Tranverse Process Osteosarcoma

Introduction Osteosarcoma (OSA) is the most common primary bone tumor in dogs. Between 20 and 25% of canine OSA arise from bones of the axial skeleton and are also the most common extradural spinal neoplasm (46%). Radiographic appearance is nonspecific and inconsistent. Pain without neurological signs is the predominant initial finding with vertebral OSA. Materials and Methods A 8 years cross-bred male dog was presented for consultation complaining of progressive weight loss, apathy and nonspecific pain. A paralumbar mass on the left side was diagnosed after clinical and radiographical examination. Cytology of the mass was performed and the animal was hospitalized for pain control and nutritional support until definitive diagnosis. During hospitalization, the clinical status of the animal deteriorated emerging neurological abnormalities. The cytology revealed the presence of cells characteristic of a neoplastic process of mesenchymal origin, apparently sarcoma. It was decided to perform a myelogram wich revealed spinal cord compression at L4, caused by the mass. Due to the deterioration of clinical status and the diagnosis owners decided for euthanasia. Results At necropsy was observedthe thickening of the transverse process of L4 vertebra by a mass with 6.3 x 7.0 x 4.5 cm. The histopathological diagnosis revealed an OSA with different histologic aspects. Discussion and Conclusion An unsucessful outcome OSA was diagnosed. Aadequately treatinglocal disease ofvertebral OSA is very difficult. Surgery is an attempt to decompress dogs with neurologic deficits or intractable pain. Present recommendations are to perform surgery for decompression and institute radiation and chemotherapy.This work was supported by Portuguese Foundation for Science and Technology, Center for Studies in Education, Technologies and by Health and by strategic project PEst-OE/CED/UI4016/201

Topological Degeneracy and Vortex Manipulation in Kitaev's Honeycomb Model

The classification of loop symmetries in Kitaev's honeycomb lattice model provides a natural framework to study the Abelian topological degeneracy. We derive a perturbative low-energy effective Hamiltonian that is valid to all orders of the expansion and for all possible toroidal configurations. Using this form we demonstrate at what order the system's topological degeneracy is lifted by finite size effects and note that in the thermodynamic limit it is robust to all orders. Further, we demonstrate that the loop symmetries themselves correspond to the creation, propagation, and annihilation of fermions. We note that these fermions, made from pairs of vortices, can be moved with no additional energy cost

Qudit versions of the qubit "pi-over-eight" gate

When visualised as an operation on the Bloch sphere, the qubit "pi-over-eight" gate corresponds to one-eighth of a complete rotation about the vertical axis. This simple gate often plays an important role in quantum information theory, typically in situations for which Pauli and Clifford gates are insufficient. Most notably, when it supplements the set of Clifford gates then universal quantum computation can be achieved. The "pi-over-eight" gate is the simplest example of an operation from the third level of the Clifford hierarchy (i.e., it maps Pauli operations to Clifford operations under conjugation). Here we derive explicit expressions for all qudit (d-level, where d is prime) versions of this gate and analyze the resulting group structure that is generated by these diagonal gates. This group structure differs depending on whether the dimensionality of the qudit is two, three or greater than three. We then discuss the geometrical relationship of these gates (and associated states) with respect to Clifford gates and stabilizer states. We present evidence that these gates are maximally robust to depolarizing and phase damping noise, in complete analogy with the qubit case. Motivated by this and other similarities we conjecture that these gates could be useful for the task of qudit magic-state distillation and, by extension, fault-tolerant quantum computing. Very recent, independent work by Campbell, Anwar and Browne confirms the correctness of this intuition, and we build upon their work to characterize noise regimes for which noisy implementations of these gates can (or provably cannot) supplement Clifford gates to enable universal quantum computation.Comment: Version 2 changed to reflect improved distillation routines in arXiv:1205.3104v2. Minor typos fixed. 12 Pages,2 Figures,3 Table

Rigorous Calculations of Non-Abelian Statistics in the Kitaev Honeycomb Model

We develop a rigorous and highly accurate technique for calculation of the Berry phase in systems with a quadratic Hamiltonian within the context of the Kitaev honeycomb lattice model. The method is based on the recently found solution of the model which uses the Jordan-Wigner-type fermionization in an exact effective spin-hardcore boson representation. We specifically simulate the braiding of two non-Abelian vortices (anyons) in a four vortex system characterized by a two-fold degenerate ground state. The result of the braiding is the non-Abelian Berry matrix which is in excellent agreement with the predictions of the effective field theory. The most precise results of our simulation are characterized by an error on the order of $10^{-5}$ or lower. We observe exponential decay of the error with the distance between vortices, studied in the range from one to nine plaquettes. We also study its correlation with the involved energy gaps and provide preliminary analysis of the relevant adiabaticity conditions. The work allows to investigate the Berry phase in other lattice models including the Yao-Kivelson model and particularly the square-octagon model. It also opens the possibility of studying the Berry phase under non-adiabatic and other effects which may constitute important sources of errors in topological quantum computation.Comment: 27 pages, 9 figures, 3 appendice

Canine mastocytosis

Mastocytosis is a mast cell disorder in which its exaggerated proliferation can occur in two forms: systemic and cutaneous (Davis et al., 1992). Because canine mastocytosis is a rare situation of controversial and difficult diagnosis, the goal of this study consists in a current revision of this subject, in order to sensitize the veterinary staff to its severity, with particular focus on the information the veterinary nurse must hold to better apply a specialized nursing care with the high professionalismFCT/CI&DETS (PEst-OE/CED/UI4016/2011

Thymic Squamous Cell Carcinoma? Do you confirm this diagnosis?

Introduction In dogs thymic carcinoma is considered rare and distinguishes itself from thymoma by its cytologically malignant features, extensive local invasion, and a substantial potential for metastasis. Surgical excision is the treatment of choice for most thymic tumours, with the exception of lymphoma. Medical History A 9 years old cross-breed male dog was presented due to cough and respiratory distress with duration of 4 weeks. The animal presented with inspiratory dyspnea and cyanosis. A mass, dorsal to the pharynx, was diagnosed after clinical and radiographical examination, suspected of thyroid neoplasia. Cytology was performed and revealed cells consistent with malignancy, apparently carcinoma with high parameters of aggressiveness. As a form of treatment and to obtain a definitive diagnosis, was decided to surgical removed the mass which measured 7.8x3.7x3.5cm. Material and Methods The sample was fixed in 10 % buffered formalin solution for histological evaluation and sent to the Anatomic Pathology Laboratory of the Agrarian Superior School of Viseu, in Portugal, for histological evaluation. Results Microscopic examination revealed that we were in presence of a lymphoid organ, with peculiar features, namely a small to intermediate-sized lymphoid cells, "starry-sky" pattern and rounded eosinophilic perivascular arrangements resembling Hassall's corpuscles. Concomitantly, typical features of squamous cell carcinoma were evident. Discussion and Conclusion In conclusion, based on its histological features, the authors suggested the diagnosis of Thymic Squamous Cell Carcinoma with an unusual location. Thymic tumours in dogs are predominantly located in the anterior mediastinum but they may extend from the neck to the posterior mediastinum.This work was supported by Portuguese Foundation for Science and Technology, Center for Studies in Education, Technologies and by Health and by strategic project PEst-OE/CED/UI4016/201

Inverted papilloma in Russian Hamster

Introduction: Cutaneous papilloma is a benign epithelial neoplasm arising in epidermal keratinocytes. Papillomaviruses belong to papovavirus family, causing single or multiple verrucous projections, variable in size, well circumscribed and keratinized. This type of tumour is common in horses, cattle and humans; less frequent in dogs and goats and rare in sheep, pigs, cats, guinea pigs and hamsters. Medical History: A 1-and a half year old entire Russian hamster was presented with a right lateral axilar subcutaneous ulcerated nodule. No other abnormalities were detected on clinical examination. The approach taken was total surgical excision. Material and Methods: The samples were fixed in 10 % buffered formalin solution for histological evaluation and were sent to the Anatomic Pathology Laboratory of the Agrarian Superior School of Viseu, in Portugal. Results: Macroscopically, the cut section revealed whitish tissues with radiated aspect, converging on the ulcerated area. Microscopic examination revealed a cystic cavity, lined by hiperplasic squamous epithelium, apparently inverted, with ortho and parakeratotic hyperkeratosis, presenting peniforme pattern. The epithelium showed acanthosis, hypergranulosis, with very large keratohyalin granules. Koilocytosis was also observed, as well as sparse eosinophilic intracytoplasmic bodies, in the cells with ballooning degeneration. Discussion and Conclusion: The histopathological features observed were compatible with the diagnosis of papilloma. However, the uncharacteristic inverted image of the epithelium, producing keratin convergent to the cystic cavity, which acquired a peniforme appearance, would fit the descriptions of inverted papilloma, although, apparently, this type of tumor, especially of such large dimensions, never been described in the hamster.This work was supported by Portuguese Foundation for Science and Technology, Center for Studies in Education, Technologies and by Health and by strategic project PEst-OE/CED/UI4016/201

Optimizing entangling quantum gates for physical systems

Optimal control theory is a versatile tool that presents a route to significantly improving figures of merit for quantum information tasks. We combine it here with the geometric theory for local equivalence classes of two-qubit operations to derive an optimization algorithm that determines the best entangling two-qubit gate for a given physical setting. We demonstrate the power of this approach for trapped polar molecules and neutral atoms.Comment: extended version; Phys. Rev. A (2011

Minimum construction of two-qubit quantum operations

Optimal construction of quantum operations is a fundamental problem in the realization of quantum computation. We here introduce a newly discovered quantum gate, B, that can implement any arbitrary two-qubit quantum operation with minimal number of both two- and single-qubit gates. We show this by giving an analytic circuit that implements a generic nonlocal two-qubit operation from just two applications of the B gate. We also demonstrate that for the highly scalable Josephson junction charge qubits, the B gate is also more easily and quickly generated than the CNOT gate for physically feasible parameters.Comment: 4 page