Control of bone remodelling by applied dynamic loads

The data showing the relationship between bone mass and peak strain magnitude prepared and submitted for publication. The data from experiments relating remodelling activity with static or dynamic loads were prepared and submitted for publication. Development of programs to relate the location of remodelling activity with he natural and artificial dynamic strain distributions continued. Experiments on the effect of different strain rates on the remodelling response continued

Static versus dynamic loads as an influence on bone remodelling

Bone remodelling activity in the avian ulna was assessed under conditions of disuse alone, disuse with a superimposed continuous compressive load, and disuse interrupted by a short daily period of intermittent loading. The ulna preparation is made by two submetaphyseal osteotomies, the cut ends of the bone being covered with stainless steel caps which, together with the bone they enclosed, are pierced by pins emerging transcutaneously on the dorsal and ventral surfaces of the wing. The 110 mm long undisturbed section of the bone shaft can be protected from functional loading, loaded continuously in compression by joining the pins with springs, or loaded intermittently in compression by engaging the pins in an Instron machine. Similar loads (525 n) were used in both static and dynamic cases engendering similar peak strains at the bone's midshaft (-2000 x 10-6). The intermitent load was applied at a frequency of 1 Hz during a single 100 second period per day as a ramped square wave, with a rate of change of strain during the ramp of 0.01 per second

Shor's quantum factoring algorithm on a photonic chip

Shor's quantum factoring algorithm finds the prime factors of a large number exponentially faster than any other known method a task that lies at the heart of modern information security, particularly on the internet. This algorithm requires a quantum computer a device which harnesses the `massive parallelism' afforded by quantum superposition and entanglement of quantum bits (or qubits). We report the demonstration of a compiled version of Shor's algorithm on an integrated waveguide silica-on-silicon chip that guides four single-photon qubits through the computation to factor 15.Comment: 2 pages, 1 figur

Manipulating biphotonic qutrits

Quantum information carriers with higher dimension than the canonical qubit offer significant advantages. However, manipulating such systems is extremely difficult. We show how measurement induced non-linearities can be employed to dramatically extend the range of possible transforms on biphotonic qutrits; the three level quantum systems formed by the polarisation of two photons in the same spatio-temporal mode. We fully characterise the biphoton-photon entanglement that underpins our technique, thereby realising the first instance of qubit-qutrit entanglement. We discuss an extension of our technique to generate qutrit-qutrit entanglement and to manipulate any bosonic encoding of quantum information.Comment: 4 pages, 4 figure

Sclerostin's role in bone's adaptive response to mechanical loading

Mechanical loading is the primary functional determinant of bone mass and architecture, and osteocytes play a key role in translating mechanical signals into (re)modelling responses. Although the precise mechanisms remain unclear, Wnt signalling pathway components, and the anti-osteogenic canonical Wnt inhibitor Sost/sclerostin in particular, play an important role in regulating bone's adaptive response to loading. Increases in loading-engendered strains down-regulate osteocyte sclerostin expression, whereas reduced strains, as in disuse, are associated with increased sclerostin production and bone loss. However, while sclerostin up-regulation appears to be necessary for the loss of bone with disuse, the role of sclerostin in the osteogenic response to loading is more complex. While mice unable to down-regulate sclerostin do not gain bone with loading, Sost knockout mice have an enhanced osteogenic response to loading. The molecular mechanisms by which osteocytes sense and transduce loading-related stimuli into changes in sclerostin expression remain unclear but include several, potentially interlinked, signalling cascades involving periostin/integrin, prostaglandin, estrogen receptor, calcium/NO and Igf signalling. Deciphering the mechanisms by which changes in the mechanical environment regulate sclerostin production may lead to the development of therapeutic strategies that can reverse the skeletal structural deterioration characteristic of disuse and age-related osteoporosis and enhance bones' functional adaptation to loading. By enhancing the osteogenic potential of the context in which individual therapies such as sclerostin antibodies act it may become possible to both prevent and reverse the age-related skeletal structural deterioration characteristic of osteoporosis

Quantum Algorithm for Molecular Properties and Geometry Optimization

It is known that quantum computers, if available, would allow an exponential decrease in the computational cost of quantum simulations. We extend this result to show that the computation of molecular properties (energy derivatives) could also be sped up using quantum computers. We provide a quantum algorithm for the numerical evaluation of molecular properties, whose time cost is a constant multiple of the time needed to compute the molecular energy, regardless of the size of the system. Molecular properties computed with the proposed approach could also be used for the optimization of molecular geometries or other properties. For that purpose, we discuss the benefits of quantum techniques for Newton's method and Householder methods. Finally, global minima for the proposed optimizations can be found using the quantum basin hopper algorithm, which offers an additional quadratic reduction in cost over classical multi-start techniques.Comment: 6 page

Calculating Unknown Eigenvalues with a Quantum Algorithm

Quantum algorithms are able to solve particular problems exponentially faster than conventional algorithms, when implemented on a quantum computer. However, all demonstrations to date have required already knowing the answer to construct the algorithm. We have implemented the complete quantum phase estimation algorithm for a single qubit unitary in which the answer is calculated by the algorithm. We use a new approach to implementing the controlled-unitary operations that lie at the heart of the majority of quantum algorithms that is more efficient and does not require the eigenvalues of the unitary to be known. These results point the way to efficient quantum simulations and quantum metrology applications in the near term, and to factoring large numbers in the longer term. This approach is architecture independent and thus can be used in other physical implementations

Adding control to arbitrary unknown quantum operations

While quantum computers promise significant advantages, the complexity of quantum algorithms remains a major technological obstacle. We have developed and demonstrated an architecture-independent technique that simplifies adding control qubits to arbitrary quantum operations-a requirement in many quantum algorithms, simulations and metrology. The technique is independent of how the operation is done, does not require knowledge of what the operation is, and largely separates the problems of how to implement a quantum operation in the laboratory and how to add a control. We demonstrate an entanglement-based version in a photonic system, realizing a range of different two-qubit gates with high fidelity.Comment: 9 pages, 8 figure

Experimental feedback control of quantum systems using weak measurements

A goal of the emerging field of quantum control is to develop methods for quantum technologies to function robustly in the presence of noise. Central issues are the fundamental limitations on the available information about quantum systems and the disturbance they suffer in the process of measurement. In the context of a simple quantum control scenario--the stabilization of non-orthogonal states of a qubit against dephasing--we experimentally explore the use of weak measurements in feedback control. We find that, despite the intrinsic difficultly of implementing them, weak measurements allow us to control the qubit better in practice than is even theoretically possible without them. Our work shows that these more general quantum measurements can play an important role for feedback control of quantum systems.Comment: 4 pages, 3 figures. v2 Added extra citation, journal reference and DOI. Minor typographic correction