1,776 research outputs found
Ultimate limits to quantum metrology and the meaning of the Heisenberg limit
For the last 20 years, the question of what are the fundamental capabilities
of quantum precision measurements has sparked a lively debate throughout the
scientific community. Typically, the ultimate limits in quantum metrology are
associated with the notion of the Heisenberg limit expressed in terms of the
physical resources used in the measurement procedure. Over the years, a variety
of different physical resources were introduced, leading to a confusion about
the meaning of the Heisenberg limit. Here, we review the mainstream definitions
of the relevant resources and introduce the universal resource count, that is,
the expectation value of the generator (above its ground state) of translations
in the parameter we wish to estimate, that applies to all measurement
strategies. This leads to the ultimate formulation of the Heisenberg limit for
quantum metrology. We prove that the new limit holds for the generators of
translations with an upper-bounded spectrum.Comment: 10 pages, 6 figures, Published version: some clarifications given on
the applicability of the new limi
Towards a Quantum Software Modeling Language
We set down the principles behind a modeling language for quantum software. We present a minimal set of extensions to the well-known Unified Modeling Language (UML) that allows it to effectively model quantum software. These extensions are separate and independent of UML as a whole. As such they can be used to extend any other software modeling language, or as a basis for a completely new language. We argue that these extensions are both necessary and sufficient to model, abstractly, any piece of quantum software. Finally, we provide a small set of examples that showcase the effectiveness of the extension set
Unifying parameter estimation and the Deutsch-Jozsa algorithm for continuous variables
We reveal a close relationship between quantum metrology and the Deutsch-Jozsa algorithm on continuous-variable quantum systems. We develop a general procedure, characterized by two parameters, that unifies parameter estimation and the Deutsch-Jozsa algorithm. Depending on which parameter we keep constant, the procedure implements either the parameter-estimation protocol or the Deutsch-Jozsa algorithm. The parameter-estimation part of the procedure attains the Heisenberg limit and is therefore optimal. Due to the use of approximate normalizable continuous-variable eigenstates, the Deutsch-Jozsa algorithm is probabilistic. The procedure estimates a value of an unknown parameter and solves the Deutsch-Jozsa problem without the use of any entanglement
A Quantum Software Modeling Language
In this chapter we will discuss the development of a quantum software
modeling language. We begin by discussing the need for a quantum-specific modeling
language, and why existing 'classical' modeling languages may not be properly
suited for the task of modeling quantum software. We then proceed with a discussion
of the fundamental principles, or axioms, that any such modeling language should
adhere to. We then present ‘Q-UML’ a quantum software modeling language based on
the popular Unified modeling Language (UML). We conclude with some examples
of Q-UML that showcase the expressive power of the language, as well as the
importance of the aforementioned principles
Fundamental Limits of Classical and Quantum Imaging
Quantum imaging promises increased imaging performance over classical
protocols. However, there are a number of aspects of quantum imaging that are
not well understood. In particular, it has so far been unknown how to compare
classical and quantum imaging procedures. Here, we consider classical and
quantum imaging in a single theoretical framework and present general
fundamental limits on the resolution and the deposition rate for classical and
quantum imaging. The resolution can be estimated from the image itself. We
present a utility function that allows us to compare imaging protocols in a
wide range of applications.Comment: 4 pages, 3 figures; accepted for Physical Review Letters, with
updated title and fixed typo
Local Unitary Quantum Cellular Automata
In this paper we present a quantization of Cellular Automata. Our formalism
is based on a lattice of qudits, and an update rule consisting of local unitary
operators that commute with their own lattice translations. One purpose of this
model is to act as a theoretical model of quantum computation, similar to the
quantum circuit model. It is also shown to be an appropriate abstraction for
space-homogeneous quantum phenomena, such as quantum lattice gases, spin chains
and others. Some results that show the benefits of basing the model on local
unitary operators are shown: universality, strong connections to the circuit
model, simple implementation on quantum hardware, and a wealth of applications.Comment: To appear in Physical Review
Device-independent verifiable blind quantum computation
As progress on experimental quantum processors continues to advance, the problem of verifying the correct operation of such devices is becoming a pressing concern. The recent discovery of protocols for verifying computation performed by entangled but non-communicating quantum processors holds the promise of certifying the correctness of arbitrary quantum computations in a fully device-independent manner. Unfortunately, all known schemes have prohibitive overhead, with resources scaling as extremely high degree polynomials in the number of gates constituting the computation. Here we present a novel approach based on a combination of verified blind quantum computation and Bell state self-testing. This approach has dramatically reduced overhead, with resources scaling as only O(m4lnm) in the number of gates
Iterated gate teleportation and blind quantum computation
Blind quantum computation allows a user to delegate a computation to an untrusted server while keeping the computation hidden. A number of recent works have sought to establish bounds on the communication requirements necessary to implement blind computation, and a bound based on the no-programming theorem of Nielsen and Chuang has emerged as a natural limiting factor. Here we show that this constraint only holds in limited scenarios, and show how to overcome it using a novel method of iterated gate teleportations. This technique enables drastic reductions in the communication required for distributed quantum protocols, extending beyond the blind computation setting. Applied to blind quantum computation, this technique offers significant efficiency improvements, and in some scenarios offers an exponential reduction in communication requirements
Experiencias sobre el uso de la plataforma Arduino en prácticas de Automatización y Robótica
En los últimos años las plataformas de hardware libre han adquirido gran relevancia en el desarrollo de prototipos y en la educación en tecnología. Una plataforma de hardware libre es básicamente un diseño de sistema un electrónico microprocesador que sus autores difunden libremente y puede ser utilizado sin tener que pagar licencias. Ente la multitud de plataformas disponibles, destaca Arduino. Se caracteriza por su bajo precio, y que el software necesario para hacer funcionar la plataforma es libre y gratuito. Todo ello hace que estos dispositivos sean fácilmente accesibles por estudiantes. Este trabajo describe la aplicación de hardware libre a experimentos de laboratorio en asignaturas de ingeniería de la UA, especialmente del máster en Automática y Robótica, en las que se controlan sistemas industriales o robóticos. Esto contrasta con los experimentos clásicos en los que se emplean sistemas caros y difícilmente accesibles por el alumno. Además, los experimentos deben ser atractivos y de aplicaciones reales, para atraer el interés del alumno, con el objetivo principal de que aprenda más y mejor en el laboratorio
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