scholarly journals Continuous gaussian measurements of the free boson CFT: A model for exactly solvable and detectable measurement-induced dynamics

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Yuri Minoguchi ◽  
Peter Rabl ◽  
Michael Buchhold
Keyword(s):  
Exact Analytical Solution ◽  
Real Space ◽  
Quantum Criticality ◽  
Many Body ◽  
Elementary Model ◽  
Free Boson ◽  
Measurement Protocol ◽  
Exactly Solvable ◽  
Quantum Phenomena ◽  
The Impact

Hybrid evolution protocols, composed of unitary dynamics and repeated, weak or projective measurements, give rise to new, intriguing quantum phenomena, including entanglement phase transitions and unconventional conformal invariance. Defying the complications imposed by the non-linear and stochastic nature of the measurement process, we introduce a scenario of measurement-induced many body evolution, which possesses an exact analytical solution: bosonic Gaussian measurements. The evolution features a competition between the continuous observation of linear boson operators and a free Hamiltonian, and it is characterized by a unique and exactly solvable covariance matrix. Within this framework, we then consider an elementary model for quantum criticality, the free boson conformal field theory, and investigate in which way criticality is modified under measurements. Depending on the measurement protocol, we distinguish three fundamental scenarios (a) enriched quantum criticality, characterized by a logarithmic entanglement growth with a floating prefactor, or the loss of criticality, indicated by an entanglement growth with either (b) an area-law or (c) a volume-law. For each scenario, we discuss the impact of imperfect measurements, which reduce the purity of the wavefunction and are equivalent to Markovian decoherence, and present a set of observables, e.g., real-space correlations, the relaxation time, and the entanglement structure, to classify the measurement-induced dynamics for both pure and mixed states. Finally, we present an experimental tomography scheme, which grants access to the density operator of the system by using the continuous measurement record only.

scholarly journals Importance of charge self-consistency in first-principles description of strongly correlated systems

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Swagata Acharya ◽  
Dimitar Pashov ◽  
Alexander N. Rudenko ◽  
Malte Rösner ◽  
Mark van Schilfgaarde ◽  
...  
Keyword(s):  
Space Charge ◽  
First Principles ◽  
Order Theory ◽  
Real Space ◽  
Many Body ◽  
Perturbative Approach ◽  
Correlated Systems ◽  
Self Energy ◽  
The Impact ◽  
Self Consistency

AbstractFirst-principles approaches have been successful in solving many-body Hamiltonians for real materials to an extent when correlations are weak or moderate. As the electronic correlations become stronger often embedding methods based on first-principles approaches are used to better treat the correlations by solving a suitably chosen many-body Hamiltonian with a higher level theory. The success of such embedding theories, often referred to as second-principles, is commonly measured by the quality of self-energy Σ which is either a function of energy or momentum or both. However, Σ should, in principle, also modify the electronic eigenfunctions and thus change the real space charge distribution. While such practices are not prevalent, some works that use embedding techniques do take into account these effects. In such cases, choice of partitioning, of the parameters defining the correlated Hamiltonian, of double-counting corrections, and the adequacy of low-level Hamiltonian hosting the correlated subspace hinder a systematic and unambiguous understanding of such effects. Further, for a large variety of correlated systems, strong correlations are largely confined to the charge sector. Then an adequate nonlocal low-order theory is important, and the high-order local correlations embedding contributes become redundant. Here we study the impact of charge self-consistency within two example cases, TiSe2 and CrBr3, and show how real space charge re-distribution due to correlation effects taken into account within a first-principles Green’s function-based many-body perturbative approach is key in driving qualitative changes to the final electronic structure of these materials.

scholarly journals Interaction between Different Kinds of Quantum Phase Transitions

2021 ◽  
Vol 3 (2) ◽  
pp. 253-261
Author(s):  
Angel Ricardo Plastino ◽  
Gustavo Luis Ferri ◽  
Angelo Plastino
Keyword(s):  
Phase Transitions ◽  
Nuclear Physics ◽  
Body Problem ◽  
Quantum Phase Transitions ◽  
Quantum Phase ◽  
Exactly Solvable Models ◽  
Solvable Models ◽  
Many Body ◽  
Pairing Interaction ◽  
Exactly Solvable

We employ two different Lipkin-like, exactly solvable models so as to display features of the competition between different fermion–fermion quantum interactions (at finite temperatures). One of our two interactions mimics the pairing interaction responsible for superconductivity. The other interaction is a monopole one that resembles the so-called quadrupole one, much used in nuclear physics as a residual interaction. The pairing versus monopole effects here observed afford for some interesting insights into the intricacies of the quantum many body problem, in particular with regards to so-called quantum phase transitions (strictly, level crossings).

scholarly journals Polaron Problems in Ultracold Atoms: Role of a Fermi Sea across Different Spatial Dimensions and Quantum Fluctuations of a Bose Medium

Atoms ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 18
Author(s):  
Hiroyuki Tajima ◽  
Junichi Takahashi ◽  
Simeon Mistakidis ◽  
Eiji Nakano ◽  
Kei Iida
Keyword(s):  
Spectral Function ◽  
Einstein Condensate ◽  
Three Dimensions ◽  
Quantum Gas ◽  
Many Body ◽  
Bose Einstein Condensate ◽  
Spatial Dimensions ◽  
Three Body ◽  
Bose Einstein ◽  
The Impact

The notion of a polaron, originally introduced in the context of electrons in ionic lattices, helps us to understand how a quantum impurity behaves when being immersed in and interacting with a many-body background. We discuss the impact of the impurities on the medium particles by considering feedback effects from polarons that can be realized in ultracold quantum gas experiments. In particular, we exemplify the modifications of the medium in the presence of either Fermi or Bose polarons. Regarding Fermi polarons we present a corresponding many-body diagrammatic approach operating at finite temperatures and discuss how mediated two- and three-body interactions are implemented within this framework. Utilizing this approach, we analyze the behavior of the spectral function of Fermi polarons at finite temperature by varying impurity-medium interactions as well as spatial dimensions from three to one. Interestingly, we reveal that the spectral function of the medium atoms could be a useful quantity for analyzing the transition/crossover from attractive polarons to molecules in three-dimensions. As for the Bose polaron, we showcase the depletion of the background Bose-Einstein condensate in the vicinity of the impurity atom. Such spatial modulations would be important for future investigations regarding the quantification of interpolaron correlations in Bose polaron problems.

Many-body forces in exactly solvable field-theoretical models

1975 ◽  
Vol 25 (3) ◽  
pp. 288-301 ◽  
Author(s):  
F. Calogero ◽  
D. De Santis
Keyword(s):  
Theoretical Models ◽  
Many Body ◽  
Body Forces ◽  
Exactly Solvable

TOPOLOGICAL PRINCIPLES IN THE THEORY OF ANDERSON LOCALIZATION

2010 ◽  
Vol 24 (12n13) ◽  
pp. 1895-1949 ◽  
Author(s):  
A. M. M. Pruisken
Keyword(s):  
Quantum Hall Effect ◽  
Disordered Systems ◽  
Anderson Localization ◽  
Quantum Hall ◽  
Quantum Criticality ◽  
Theoretical Physics ◽  
Strong Magnetic Fields ◽  
Localization Theory ◽  
Quantum Phenomena ◽  
Interaction Phenomena

Scaling ideas in the theory of the quantum Hall effect are fundamentally based on topological principles in Anderson localization theory. These concepts have a very general significance and are not limited to replica field theory or disordered systems alone. In this chapter, we will discuss these ideas in several distinctly different physical contexts. We start with a brief overview that spans two and a half decades of experimental research on quantum criticality in strong magnetic fields. Secondly, we address the new understanding of universality that has emerged from the theory of Anderson localization and interaction phenomena. In the last part we show how the experimentally observed quantum phenomena fundamentally alter the way in which strong coupling problems in theoretical physics are perceived.

scholarly journals Shock-wave model of the earthquake and Poincaré quantum theorem give an insight into the aftershock physics.

2018 ◽  
Vol 62 ◽  
pp. 03006
Author(s):  
Vladimir Kuznetsov
Keyword(s):  
Shock Wave ◽  
Wave Model ◽  
Particle Systems ◽  
Many Body ◽  
Initial State ◽  
Recurrence Theorem ◽  
Shock Wave Model ◽  
Quantum Phenomena ◽  
First Time ◽  
Insight Into

A fundamentally new model of aftershocks evident from the shock-wave model of the earthquake and Poincaré Recurrence Theorem [H. Poincare, Acta Mathematica 13, 1 (1890)] is proposed here. The authors (Recurrences in an isolated quantum many-body system, Science 2018) argue that the theorem should be formulated as “Complex systems return almost exactly into their initial state”. For the first time, this recurrence theorem has been demonstrated with complex quantum multi-particle systems. Our shock-wave model of an earthquake proceeds from the quantum entanglement of protons in hydrogen bonds of lithosphere material. Clearly aftershocks are quantum phenomena which mechanism follows the recurrence theorem.

scholarly journals A New Geo-Propagation Model of Event Evolution Chain Based on Public Opinion and Epidemic Coupling

2020 ◽  
Vol 17 (24) ◽  
pp. 9235
Author(s):  
Yan Zhang ◽  
Nengcheng Chen ◽  
Wenying Du ◽  
Shuang Yao ◽  
Xiang Zheng
Keyword(s):  
Public Health ◽  
Public Opinion ◽  
Spatial Dimension ◽  
Real Space ◽  
Propagation Model ◽  
Health Events ◽  
Model Complex ◽  
Epidemic Area ◽  
Before And After ◽  
The Impact

The online public opinion is the sum of public views, attitudes and emotions spread on major public health emergencies through the Internet, which maps out the scope of influence and the disaster situation of public health events in real space. Based on the multi-source data of COVID-19 in the context of a global pandemic, this paper analyzes the propagation rules of disasters in the coupling of the spatial dimension of geographic reality and the dimension of network public opinion, and constructs a new gravity model-complex network-based geographic propagation model of the evolution chain of typical public health events. The strength of the model is that it quantifies the extent of the impact of the epidemic area on the surrounding area and the spread of the epidemic, constructing an interaction between the geographical reality dimension and online public opinion dimension. The results show that: The heterogeneity in the direction of social media discussions before and after the “closure” of Wuhan is evident, with the center of gravity clearly shifting across the Yangtze River and the cyclical changing in public sentiment; the network model based on the evolutionary chain has a significant community structure in geographic space, divided into seven regions with a modularity of 0.793; there are multiple key infection trigger nodes in the network, with a spatially polycentric infection distribution.

scholarly journals Lattice QCD input for nuclear structure and reactions

2018 ◽  
Vol 175 ◽  
pp. 01022 ◽  
Author(s):  
Zohreh Davoudi
Keyword(s):  
Quantum Chromodynamics ◽  
Nuclear Reactions ◽  
Many Body ◽  
Quark Masses ◽  
The Past ◽  
Lattice Quantum ◽  
Nuclear Systems ◽  
Community Effort ◽  
The Impact ◽  
Made In

Explorations of the properties of light nuclear systems beyond their lowestlying spectra have begun with Lattice Quantum Chromodynamics. While progress has been made in the past year in pursuing calculations with physical quark masses, studies of the simplest nuclear matrix elements and nuclear reactions at heavier quark masses have been conducted, and several interesting results have been obtained. A community effort has been devoted to investigate the impact of such Quantum Chromodynamics input on the nuclear many-body calculations. Systems involving hyperons and their interactions have been the focus of intense investigations in the field, with new results and deeper insights emerging. While the validity of some of the previous multi-nucleon studies has been questioned during the past year, controversy remains as whether such concerns are relevant to a given result. In an effort to summarize the newest developments in the field, this talk will touch on most of these topics.

Impact of a short-term exposure to spaceflight on the phenotype, genome, transcriptome and proteome ofEscherichia coli

2015 ◽  
Vol 14 (3) ◽  
pp. 435-444 ◽  
Author(s):  
Tianzhi Li ◽  
De Chang ◽  
Huiwen Xu ◽  
Jiapeng Chen ◽  
Longxiang Su ◽  
...  
Keyword(s):  
Carbon Sources ◽  
Model Organism ◽  
Opportunistic Pathogen ◽  
Real Space ◽  
Space Environment ◽  
Nucleotide Polymorphisms ◽  
E Coli ◽  
Applied Model ◽  
Short Term Exposure ◽  
The Impact

AbstractEscherichia coli(E. coli) is the most widely applied model organism in current biological science. As a widespread opportunistic pathogen,E. colican survive not only by symbiosis with human, but also outside the host as well, which necessitates the evaluation of its response to the space environment. Therefore, to keep humans safe in space, it is necessary to understand how the bacteria respond to this environment. Despite extensive investigations for a few decades, the response ofE. colito the real space environment is still controversial. To better understand the mechanisms howE. coliovercomes harsh environments such as microgravity in space and to investigate whether these factors may induce pathogenic changes inE. colithat are potentially detrimental to astronauts, we conducted detailed genomics, transcriptomic and proteomic studies onE. colithat experienced 17 days of spaceflight. By comparing two flight strains LCT-EC52 and LCT-EC59 to a control strain LCT-EC106 that was cultured under the same temperature conditions on the ground, we identified metabolism changes, polymorphism changes, differentially expressed genes and proteins in the two flight strains. The flight strains differed from the control in the utilization of more than 30 carbon sources. Two single nucleotide polymorphisms (SNPs) and one deletion were identified in the flight strains. The expression level of more than 1000 genes altered in flight strains. Genes involved in chemotaxis, lipid metabolism and cell motility express differently. Moreover, the two flight strains also differed extensively from each other in terms of metabolism, transcriptome and proteome, indicating the impact of space environment on individual cells is heterogeneous and probably genotype-dependent. This study presents the first systematic profile ofE. coligenome, transcriptome and proteome after spaceflight, which helps to elucidate the mechanism that controls the adaptation of microbes to the space environment.

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