1,720,975 research outputs found
Dynamical quantum phase transitions in spin- quantum link models
No full textDynamical quantum phase transitions (DQPTs) are a powerful concept of probing
far-from-equilibrium criticality in quantum many-body systems. With the strong
ongoing experimental drive to quantum-simulate lattice gauge theories, it
becomes important to investigate DQPTs in these models in order to better
understand their far-from-equilibrium properties. In this work, we use infinite
matrix product state techniques to study DQPTs in spin-
quantum link models. Although we are able to reproduce literature results
directly connecting DQPTs to a sign change in the dynamical order parameter in
the case of for quenches starting in a vacuum initial state, we find
that for different quench protocols or different values of the link spin length
this direct connection is no longer present. In particular, we find
that there is an abundance of different types of DQPTs not directly associated
with any sign change of the order parameter. Our findings indicate that DQPTs
are fundamentally different between the Wilson--Kogut--Susskind limit and its
representation through the quantum link formalism.Comment: 10 pages, 4 figures, journal articl
Towards the continuum limit of a d quantum link Schwinger model
Full text linkThe solution of gauge theories is one of the most promising applications of
quantum technologies. Here, we discuss the approach to the continuum limit for
gauge theories regularized via finite-dimensional Hilbert spaces of
quantum spin- operators, known as quantum link models. For quantum
electrodynamics (QED) in one spatial dimension, we numerically demonstrate the
continuum limit by extrapolating the ground state energy, the scalar, and the
vector meson masses to large spin lengths , large volume , and vanishing
lattice spacing . By exactly solving Gauss' law for arbitrary , we obtain
a generalized PXP spin model and count the physical Hilbert space dimension
analytically. This allows us to quantify the required resources for reliable
extrapolations to the continuum limit on quantum devices. We use a functional
integral approach to relate the model with large values of half-integer spins
to the physics at topological angle . Our findings indicate that
quantum devices will in the foreseeable future be able to quantitatively probe
the QED regime with quantum link models.Comment: 6+6 pages, 4+1 figure
Achieving the quantum field theory limit in far-from-equilibrium quantum link models
Full text linkRealizations of gauge theories in setups of quantum synthetic matter open up
the possibility of probing salient exotic phenomena in condensed matter and
high-energy physics, along with potential applications in quantum information
and science technologies. In light of the impressive ongoing efforts to achieve
such realizations, a fundamental question regarding quantum link model
regularizations of lattice gauge theories is how faithfully they capture the
quantum field theory limit of gauge theories. Recent work [Zache, Van Damme,
Halimeh, Hauke, and Banerjee, at
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.106.L091502 has shown
through analytic derivations, exact diagonalization, and infinite matrix
product state calculations that the low-energy physics of D
quantum link models approaches the quantum field theory limit
already at small link spin length . Here, we show that the approach to this
limit also lends itself to the far-from-equilibrium quench dynamics of lattice
gauge theories, as demonstrated by our numerical simulations of the Loschmidt
return rate and the chiral condensate in infinite matrix product states, which
work directly in the thermodynamic limit. Similar to our findings in
equilibrium that show a distinct behavior between half-integer and integer link
spin lengths, we find that criticality emerging in the Loschmidt return rate is
fundamentally different between half-integer and integer spin quantum link
models in the regime of strong electric-field coupling. Our results further
affirm that state-of-the-art finite-size ultracold-atom and NISQ-device
implementations of quantum link lattice gauge theories have the real potential
to simulate their quantum field theory limit even in the far-from-equilibrium
regime.Comment: Accepted in Quantu
Error-Corrected Fermionic Quantum Processors with Neutral Atoms
No full text7 pages, 4 figuresMany-body fermionic systems can be simulated in a hardware-efficient manner using a fermionic quantum processor. Neutral atoms trapped in optical potentials can realize such processors, where nonlocal fermionic statistics are guaranteed at the hardware level. Implementing quantum error correction in this setup is, however, challenging, due to the atom-number superselection present in atomic systems, that is, the impossibility of creating coherent superpositions of different particle numbers. In this Letter, we overcome this constraint and present a blueprint for an error-corrected fermionic quantum processor that can be implemented using current experimental capabilities. To achieve this, we first consider an ancillary set of fermionic modes and design a fermionic reference, which we then use to construct superpositions of different numbers of referenced fermions. This allows us to build logical fermionic modes that can be error corrected using standard atomic operations. Here, we focus on phase errors, which we expect to be a dominant source of errors in neutral-atom quantum processors. We then construct logical fermionic gates, and show their implementation for the logical particle-number conserving processes relevant for quantum simulation. Finally, our protocol is illustrated with a minimal fermionic circuit, where it leads to a quadratic suppression of the logical error rate.Work in Innsbruck is funded by the Horizon Europe program HORIZON-CL4-2022-QUANTUM-02-
SGA via the Project No. 101113690 (PASQuanS2.1), the ERC Starting grant QARA (Grant No. 101041435), and by the Austrian Science Fund (FWF) (Grant No. DOI 10.55776/COE1). D. G.-C. acknowledges support from the European Union’s Horizon Europe program under the Marie Skłodowska Curie Action PROGRAM (Grant No. 101150724). A. M. K. and H. P. acknowledge support from the National Science Foundation QLCI (OMA2016244). A. M. K. acknowledges support from the National Institute of Standards and Technology.Peer reviewe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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