scholarly journals On the time evolution at a fluctuating exceptional point

Nanophotonics ◽  
2019 ◽  
Vol 8 (8) ◽  
pp. 1319-1326 ◽  
Author(s):  
Christian Wolff ◽  
Christos Tserkezis ◽  
N. Asger Mortensen
Keyword(s):  
Time Evolution ◽  
Evolution Operator ◽  
Exceptional Point ◽  
Initial State ◽  
Time Evolution Operator ◽  
External Perturbations ◽  
Sensing Applications ◽  
The Mean ◽  
The Impact ◽  
Mean Time

AbstractWe theoretically evaluate the impact of drift-free noise on the dynamics of ${\cal P}{\cal T}$-symmetric non-Hermitian systems with an exceptional point, which have recently been proposed for sensors. Such systems are currently considered as promising templates for sensing applications, because of their intrinsically extremely sensitive response to external perturbations. However, this applies equally to the impact of fabrication imperfections and fluctuations in the system parameters. Here we focus on the influence of such fluctuations caused by inevitable (thermal) noise and show that the exceptional-point eigenstate is not stable in its presence. To this end, we derive an effective differential equation for the mean time evolution operator averaged over all realizations of the noise field, and via numerical analysis we find that the presence of noise leads to exponential divergence of any initial state after some characteristic period of time. We therefore show that it is rather demanding to design sensor systems based on continuous operation at an exceptional point.

scholarly journals The impact of COVID-19 infection on hip fracture 30-day mortality

Trauma ◽  
2021 ◽  
pp. 146040862094972
Author(s):  
Ahmed Fadulelmola ◽  
Rob Gregory ◽  
Gavin Gordon ◽  
Fiona Smith ◽  
Andrew Jennings
Keyword(s):  
Hip Fracture ◽  
Hip Fractures ◽  
Hospital Admissions ◽  
The Elderly ◽  
Primary Outcome Measure ◽  
Time To Death ◽  
Significant Difference ◽  
The Mean ◽  
The Impact ◽  
Mean Time

Introduction: A novel virus, SARS-CoV-2, has caused a fatal global pandemic which particularly affects the elderly and those with comorbidities. Hip fractures affect elderly populations, necessitate hospital admissions and place this group at particular risk from COVID-19 infection. This study investigates the effect of COVID-19 infection on 30-day hip fracture mortality. Method: Data related to 75 adult hip fractures admitted to two units during March and April 2020 were reviewed. The mean age was 83.5 years (range 65–98 years), and most (53, 70.7%) were women. The primary outcome measure was 30-day mortality associated with COVID-19 infection. Results: The COVID-19 infection rate was 26.7% (20 patients), with a significant difference in the 30-day mortality rate in the COVID-19-positive group (10/20, 50%) compared to the COVID-19-negative group (4/55, 7.3%), with mean time to death of 19.8 days (95% confidence interval: 17.0–22.5). The mean time from admission to surgery was 43.1 h and 38.3 h, in COVID-19-positive and COVID-19-negative groups, respectively. All COVID-19-positive patients had shown symptoms of fever and cough, and all 10 cases who died were hypoxic. Seven (35%) cases had radiological lung findings consistent of viral pneumonitis which resulted in mortality (70% of mortality). 30% ( n = 6) contracted the COVID-19 infection in the community, and 70% ( n = 14) developed symptoms after hospital admission. Conclusion: Hip fractures associated with COVID-19 infection have a high 30-day mortality. COVID-19 testing and chest X-ray for patients presenting with hip fractures help in early planning of high-risk surgeries and allow counselling of the patients and family using realistic prognosis.

scholarly journals Complexity growth in integrable and chaotic models

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Vijay Balasubramanian ◽  
Matthew DeCross ◽  
Arjun Kar ◽  
Yue Li ◽  
Onkar Parrikar
Keyword(s):  
Time Evolution ◽  
Evolution Operator ◽  
Linear Growth ◽  
Conjugate Points ◽  
Majorana Fermions ◽  
Time Evolution Operator ◽  
Free Theory ◽  
Group Manifold ◽  
Geodesic Length ◽  
Evolution Trajectory

Abstract We use the SYK family of models with N Majorana fermions to study the complexity of time evolution, formulated as the shortest geodesic length on the unitary group manifold between the identity and the time evolution operator, in free, integrable, and chaotic systems. Initially, the shortest geodesic follows the time evolution trajectory, and hence complexity grows linearly in time. We study how this linear growth is eventually truncated by the appearance and accumulation of conjugate points, which signal the presence of shorter geodesics intersecting the time evolution trajectory. By explicitly locating such “shortcuts” through analytical and numerical methods, we demonstrate that: (a) in the free theory, time evolution encounters conjugate points at a polynomial time; consequently complexity growth truncates at O($$ \sqrt{N} $$ N ), and we find an explicit operator which “fast-forwards” the free N-fermion time evolution with this complexity, (b) in a class of interacting integrable theories, the complexity is upper bounded by O(poly(N)), and (c) in chaotic theories, we argue that conjugate points do not occur until exponential times O(eN), after which it becomes possible to find infinitesimally nearby geodesics which approximate the time evolution operator. Finally, we explore the notion of eigenstate complexity in free, integrable, and chaotic models.

scholarly journals Preparation of Approximate Eigenvector by Unitary Operations on Eigenstate in Abrams-Lloyd Quantum Algorithm

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Latha S. Warrier
Keyword(s):  
Time Evolution ◽  
Programming Language ◽  
Spin Chain ◽  
Evolution Operator ◽  
Unitary Operator ◽  
Language Model ◽  
Quantum Algorithm ◽  
Basis Vector ◽  
Unitary Matrix ◽  
Time Evolution Operator

The Abrams-Lloyd quantum algorithm computes an eigenvalue and the corresponding eigenstate of a unitary matrix from an approximate eigenvector Va. The eigenstate is a basis vector in the orthonormal eigenspace. Finding another eigenvalue, using a random approximate eigenvector, may require many trials as the trial may repeatedly result in the eigenvalue measured earlier. We present a method involving orthogonalization of the eigenstate obtained in a trial. It is used as the Va for the next trial. Because of the orthogonal construction, Abrams-Lloyd algorithm will not repeat the eigenvalue measured earlier. Thus, all the eigenvalues are obtained in sequence without repetitions. An operator that anticommutes with a unitary operator orthogonalizes the eigenvectors of the unitary. We implemented the method on the programming language model of quantum computation and tested it on a unitary matrix representing the time evolution operator of a small spin chain. All the eigenvalues of the operator were obtained sequentially. Another use of the first eigenvector from Abrams-Lloyd algorithm is preparing a state that is the uniform superposition of all the eigenvectors. This is possible by nonorthogonalizing the first eigenvector in all dimensions and then applying the Abrams-Lloyd algorithm steps stopping short of the last measurement.

Patient Access to Hepatitis C Treatment After Incorporation of Pharmacists in a Hepatology Clinic

2021 ◽  
pp. 001857872110375
Author(s):  
Frank A. Fanizza ◽  
Jennifer Loucks ◽  
Angelica Berni ◽  
Meera Shah ◽  
Dennis Grauer ◽  
...  
Keyword(s):  
Hepatitis C ◽  
Medication Adherence ◽  
Hcv Treatment ◽  
Clinical Pharmacists ◽  
The Mean ◽  
Group 2 ◽  
Cure Rates ◽  
The Impact ◽  
Mean Time ◽  
Group 1

Background: Modern hepatitis C virus (HCV) treatment regimens yield cure rates greater than 90%. However, obtaining approval for treatment through the prior authorization (PA) process can be time consuming and require extensive documentation. Lack of experience with this complex process can delay HCV medication approval, ultimately increasing the amount of time before patients start treatment and in some cases, prevent treatment altogether. Objectives: Assess the impact of incorporating clinical pharmacists into specialty pharmacy and hepatology clinic services on medication access, patient adherence, and outcomes in patients being treated for HCV. Methods: We performed a retrospective cohort exploratory study of patients seen in an academic medical center hepatology clinic who had HCV prescriptions filled between 8/1/15 and 7/31/17. Patients were categorized by whether they filled prescriptions prior to (Pre-Group) or after (Post-Group) the implementation of a pharmacist in clinic. The Post-Group was further divided according to whether the patient was seen by a pharmacist in clinic (Post-Group 2) or if the patient was not seen by the pharmacist, but had their HCV therapy evaluated by the pharmacist before seeking insurance approval (Post-Group 1). Results: The mean time from the prescription being ordered to being dispensed was longer in the Pre-Group (50.8 ± 66.5 days) compared to both Post-Groups (22.2 ± 27.8 days in Post-Group 1 vs 18.9 ± 17.7 days in Post-Group 2; P < .05). The mean time from when the prescription was ordered to when the PA was submitted was longer in the Pre-Group (41.6 ± 71.9 days) compared to both Post-Groups (6.3 ± 16 in Post-Group 1 vs 4.1 ± 9.7 in Post-Group 2; P < .05). Rates of medication adherence and sustained virologic response were similar between all groups. Conclusion: Incorporation of clinical pharmacists into a hepatology clinic significantly reduced the time patients waited to start HCV treatment. In addition to improving access to medications, implementation of the model helped to maintain excellent medication adherence and cure rates.

Telephone Calls to an Infectious Diseases Fellow

PEDIATRICS ◽  
1995 ◽  
Vol 95 (5) ◽  
pp. 753-754
Author(s):  
Mark F. Cotton
Keyword(s):  
Infectious Disease ◽  
Infectious Diseases ◽  
Time Allocation ◽  
Primary Care Physicians ◽  
First Year ◽  
Educational Value ◽  
The Mean ◽  
Telephone Calls ◽  
The Impact ◽  
Mean Time

Objective. There is no information on the impact and nature of telephone calls directed to subspecialists. The main objective was to document prospectively all calls directed to a first-year infectious diseases fellow, to determine their content, origin, educational value, and time allocation. Results. Three hundred fifty-nine calls were received over a 71-day period from March 24 through May 20, 1992. The mean number of daily calls was 5.1 ± 3.3. Mean time per call was 7 ± 5.4 minutes. Cumulatively, 41.7 hours were spent responding to telephone calls. The subgroup with the most calls (44.3%) was from pediatricians in practice. Seventy percent of calls were for advice about case management. Forty percent of calls were considered educational to the fellow. Conclusions. This study confirms the importance of the infectious disease subspecialist as a resource for primary care physicians.

Erratum: Unitary expansion of the time evolution operator [Phys. Rev. A82, 042110 (2010)]

2011 ◽  
Vol 84 (1) ◽  
Author(s):  
N. Zagury ◽  
A. Aragão ◽  
J. Casanova ◽  
E. Solano
Keyword(s):  
Time Evolution ◽  
Evolution Operator ◽  
Time Evolution Operator
Sign in / Sign up

Export Citation Format

Share Document