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A global picture is drawn tying together most exact cosmological solutions of gravitational theories in four or more spacetime dimensions.

General Relativity and Quantum Cosmology · Physics 2014-11-17 Robert T. Jantzen

The present short review article illustrates the latest theoretical developments on quantum tomography, regarding general optimization methods for both data-processing and setup. The basic theoretical tool is the informationally complete…

We solve the long-standing problem of making n perfect clones from m copies of one of two known pure states with minimum failure probability in the general case where the known states have arbitrary a priori probabilities. The solution…

Quantum Physics · Physics 2016-05-25 Vadim Yerokhin , Andi Shehu , Edgar Feldman , Emilio Bagan , Janos A. Bergou

We derive the transformation for the optimal universal quantum anti-cloner which produces two anti-parallel outputs for a single input state. The fidelity is shown to be 2/3 which is same as the measurement fidelity. We consider a…

Quantum Physics · Physics 2007-05-23 David D. Song , Lucien Hardy

An optimal local conversion strategy between any two pure states of a bipartite system is presented. It is optimal in that the probability of success is the largest achievable if the parties which share the system, and which can communicate…

Quantum Physics · Physics 2009-10-31 Guifre Vidal

An universal approximation technique for analysis of different characteristics of states of composite infinite-dimensional quantum systems is proposed and used to prove general results concerning the properties of correlation and…

Quantum Physics · Physics 2024-11-01 M. E. Shirokov

In classical control theory, tracking refers to the ability to perform measurements and feedback on a classical system in order to enforce some desired dynamics. In this paper we investigate a simple version of quantum tracking, namely, we…

Quantum Physics · Physics 2008-11-20 Paulo E. M. F. Mendonca , Alexei Gilchrist , Andrew C. Doherty

Quantum operations (QO) describe any state change allowed in quantum mechanics, such as the evolution of an open system or the state change due to a measurement. We address the problem of which unitary transformations and which observables…

Quantum Physics · Physics 2009-11-10 F. Buscemi , G. M. D'Ariano , M. F. Sacchi

We present filling as a type of spatial subdivision problem similar to covering and packing. Filling addresses the optimal placement of overlapping objects lying entirely inside an arbitrary shape so as to cover the most interior volume. In…

Soft Condensed Matter · Physics 2015-06-04 Carolyn L. Phillips , Joshua A. Anderson , Greg Huber , Sharon C. Glotzer

We study the problem of the practical realization of an abstract quantum circuit when executed on quantum hardware. By practical, we mean adapting the circuit to particulars of the physical environment which restricts/complicates the…

Quantum Physics · Physics 2008-03-27 D. Maslov , S. M. Falconer , M. Mosca

We develop an approximation approach to infinite dimensional quantum channels based on detailed investigation of the continuity properties of entropic characteristics of quantum channels and operations (trace-nonincreasing completely…

Quantum Physics · Physics 2008-12-17 M. E. Shirokov , A. S. Holevo

We provide optimal measurement schemes for estimating relative parameters of the quantum state of a pair of spin systems. We prove that the optimal measurements are joint measurements on the pair of systems, meaning that they cannot be…

Quantum Physics · Physics 2007-05-23 Stephen D. Bartlett , Terry Rudolph , Robert W. Spekkens

We provide the optimal strategy for unambiguous quantum reading of optical memories, namely when perfect retrieving of information is achieved probabilistically, for the case where noise and loss are negligible. We describe the experimental…

Quantum Layout Synthesis (QLS) maps a logical quantum circuit to a physical quantum platform. Optimal QLS minimizes circuit size and depth, which is essential to reduce the noise on current quantum platforms. Optimal QLS is an NP-hard…

Quantum Physics · Physics 2025-07-18 Kostiantyn V. Milkevych , Jaco van de Pol , Irfansha Shaik

A general formalism of the problem of perfect state transfer is presented. We show that there are infinitely many Hamiltonians which may provide solution to this problem. In a first attempt to give a classification of them we investigate…

Quantum Physics · Physics 2007-05-23 V. Kost'ak , G. M. Nikolopoulos , I. Jex

Many problems of industrial interest are NP-complete, and quickly exhaust resources of computational devices with increasing input sizes. Quantum annealers (QA) are physical devices that aim at this class of problems by exploiting quantum…

For N=1 supergravity in 3+1 dimensions we determine the graded algebra of the quantized Lorentz generators, supersymmetry generators, and diffeo-morphism and Hamiltonian generators and find that, at least formally, it closes in the chosen…

General Relativity and Quantum Cosmology · Physics 2010-01-08 Andras Csordas , Robert Graham

Consider the following variant of the set cover problem. We are given a universe $U=\{1,...,n\}$ and a collection of subsets $\mathcal{C} = \{S_1,...,S_m\}$ where $S_i \subseteq U$. For every element $u \in U$ we need to find a set $\phi(u)…

Computational Complexity · Computer Science 2017-07-07 Marek Adamczyk , Fabrizio Grandoni , Stefano Leonardi , MIchal Wlodarczyk

Quantum computing has the potential to significantly speed up complex computational tasks, and arguably the most promising application area for near-term quantum computers is the simulation of quantum mechanics. To make the most of our…

Quantum Physics · Physics 2019-12-10 Sean A. Fischer , Daniel Gunlycke

Characterizing thermally activated transitions in high-dimensional rugged energy surfaces is a very challenging task for classical computers. Here, we develop a quantum annealing scheme to solve this problem. First, the task of finding the…

Quantum Physics · Physics 2021-01-18 Philipp Hauke , Giovanni Mattiotti , Pietro Faccioli