Search results for "Quantum algorithm"
showing 10 items of 103 documents
Quantum control theory for decoherence suppression in quantum gates
2007
We show how quantum optimal control theory can help achieve high-fidelity quantum gates in real experimental settings. We discuss several optimization methods (from iterative algorithms to optimization by interference and to impulsive control) and different physical scenarios (from optical lattices to atom chips and to Rydberg atoms).
Hybrid discrete- and continuous-variable quantum information
2015
Research in quantum information processing has followed two different directions: the use of discrete variables (qubits) and that of high-dimensional, continuous-variable Gaussian states (coherent and squeezed states). Recently, these two approaches have been converging in potentially more powerful hybrid protocols. The traditional approaches to quantum information processing using either discrete or continuous variables can be combined in hybrid protocols for tasks including quantum teleportation, computation, entanglement distillation or Bell tests.
Quantum Computing: A Way to Break Complexity?
2003
The perception of time is given by the happening of some events that determines a variation in the state of the observed system. In this sense a computation, i.e. a set of well defined transformations that, starting from an initial state (the input) brings to a final state (the output), can be considered a time generator. Each ticking of the clock corresponds to the computer changes of its states. The speed of computation leads to a different perception of time as well as traveling by airplanes changed the perception of spatial distances.
Quantum Query Algorithms for Conjunctions
2010
Every Boolean function can be presented as a logical formula in conjunctive normal form. Fast algorithm for conjunction plays significant role in overall algorithm for computing arbitrary Boolean function. First, we present a quantum query algorithm for conjunction of two bits. Our algorithm uses one quantum query and correct result is obtained with a probability p = 4/5, that improves the previous result. Then, we present the main result - generalization of our approach to design efficient quantum algorithms for computing conjunction of two Boolean functions. Finally, we demonstrate another kind of an algorithm for conjunction of two bits, that has a correct answer probability p = 9/10. Th…
Quantum Algorithm for Distribution-Free Junta Testing
2019
Inspired by a recent classical distribution-free junta tester by Chen, Liu, Serverdio, Sheng, and Xie (STOC’18), we construct a quantum tester for the same problem with complexity \(O(k/\varepsilon )\), which constitutes a quadratic improvement.
Quantum Dual Adversary for Hidden Subgroups and Beyond
2019
An explicit quantum dual adversary for the S-isomorphism problem is constructed. As a consequence, this gives an alternative proof that the query complexity of the dihedral hidden subgroup problem is polynomial.
Quantum Property Testing for Bounded-Degree Graphs
2011
We study quantum algorithms for testing bipartiteness and expansion of bounded-degree graphs. We give quantum algorithms that solve these problems in time O(N^(1/3)), beating the Omega(sqrt(N)) classical lower bound. For testing expansion, we also prove an Omega(N^(1/4)) quantum query lower bound, thus ruling out the possibility of an exponential quantum speedup. Our quantum algorithms follow from a combination of classical property testing techniques due to Goldreich and Ron, derandomization, and the quantum algorithm for element distinctness. The quantum lower bound is obtained by the polynomial method, using novel algebraic techniques and combinatorial analysis to accommodate the graph s…
Properties and application of nondeterministic quantum query algorithms
2006
Many quantum algorithms can be analyzed in a query model to compute Boolean functions where input is given by a black box. As in the classical version of decision trees, different kinds of quantum query algorithms are possible: exact, zero-error, bounded-error and even nondeterministic. In this paper, we study the latter class of algorithms. We introduce a fresh notion in addition to already studied nondeterministic algorithms and introduce dual nondeterministic quantum query algorithms. We examine properties of such algorithms and prove relations with exact and nondeterministic quantum query algorithm complexity. As a result and as an example of the application of discovered properties, we…
Quantum algorithm complexity
2008
Elektroniskā versija nesatur pielikumus
Unveiling the Effect of Magnetic Noise in the Coherence of Single-Molecule Quantum Processors.
2019
Quantum bits (qubits) constitute the most elementary building-blocks of any quantum technology, where information is stored and processed in the form of quantum superpositions between discrete energy levels. In particular, the fabrication of quantum processors is a key long-term goal that will allow us conducting specific tasks much more efficiently than the most powerful classical computers can do. Motivated by recent experiments in which three addressable spin qubits are defined on a potential single-molecule quantum processor, namely the [Gd(H2O)P5W30O110]12− polyoxometalate, we investigate the decohering effect of magnetic noise on the encoded quantum information. Our state-of-the-art m…