We study the robustness of the evolution of a quantum system against small uncontrolled variations in parameters in the Hamiltonian. We show that the fidelity susceptibility, which quantifies the perturbative error to leading order, can be expressed in superoperator form and use this to derive control pulses that are robust to any class of systematic unknown errors. The proposed optimal control protocol is equivalent to searching for a sequence of unitaries that mimics the first-order moments of the Haar distribution, i.
View Article and Find Full Text PDFWe investigate the thermodynamics of a hybrid quantum device consisting of two qubits collectively interacting with a quantum rotor and coupled dissipatively to two equilibrium reservoirs at different temperatures. By modeling the dynamics and the resulting steady state of the system using a collision model, we identify the functioning of the device as a thermal engine, a refrigerator, or an accelerator. In addition, we also look into the device's capacity to operate as a heat rectifier and optimize both the rectification coefficient and the heat flow simultaneously.
View Article and Find Full Text PDFThoracic spine CTs are usually performed during free breathing and with a narrow field of view; this common practice systematically excludes the assessment of lungs and other extraspinal structures, even if these have been irradiated during the examination. At our institution we perform thoracic spine CT during breath hold with additional full FOV reconstructions; this allows us to also evaluate lungs and extraspinal pathologies in the same examination with no added costs or further radiation exposure. If this simple and costless technical change is routinely applied to thoracic spine CT many concomitant extraspinal pathologies can be ruled out, from neoplasms to pneumonia; the suggested modification also allows an early diagnosis and avoids recalling and re-irradiating the patient in case these findings are partially included in the study.
View Article and Find Full Text PDFWe introduce the multipartite collision model, defined in terms of elementary interactions between subsystems and ancillas, and show that it can simulate the Markovian dynamics of any multipartite open quantum system. We develop a method to estimate an analytical error bound for any repeated interactions model, and we use it to prove that the error of our scheme displays an optimal scaling. Finally, we provide a simple decomposition of the multipartite collision model into elementary quantum gates, and show that it is efficiently simulable on a quantum computer according to the dissipative quantum Church-Turing theorem, i.
View Article and Find Full Text PDFIn this work, we study the performance of a quasistatic and quantum-adiabatic magnetic Otto cycles with a working substance composed of a single graphene quantum dot modeled by the continuum approach with the use of the zigzag boundary condition. Modulating an external or perpendicular magnetic field, in the quasistatic approach, we found a constant behavior in the total work extracted that is not present in the quantum-adiabatic formulation. We find that, in the quasistatic approach, the engine yielded a greater performance in terms of total work extracted and efficiency as compared with its quantum-adiabatic counterpart.
View Article and Find Full Text PDFWe propose a three-qubit setup for the implementation of a variety of quantum thermal machines where all heat fluxes and work production can be controlled. An important configuration that can be designed is that of an absorption refrigerator, extracting heat from the coldest reservoir without the need of external work supply. Remarkably, we achieve this regime by using only two-body interactions instead of the widely employed three-body interactions.
View Article and Find Full Text PDFBackground: Few data are known regarding the molecular features and patterns of growth and presentation which characterize those lung neoplastic lesions presenting as non-solid nodules (NSN).
Methods: We retrospectively reviewed two different cohorts of NSNs detected by CT scan which, after transthoracic fine-needle aspiration (FNA) and core needle biopsy (CNB) received a final diagnosis of malignancy. All the enrolled patients were then addressed to surgical removal of lung cancer nodules or to exclusive radiotherapy.
We introduce the idea of weakly coherent collisional models, where the elements of an environment interacting with a system of interest are prepared in states that are approximately thermal but have an amount of coherence proportional to a short system-environment interaction time in a scenario akin to well-known collisional models. We show that, in the continuous-time limit, the model allows for a clear formulation of the first and second laws of thermodynamics, which are modified to include a nontrivial contribution related to quantum coherence. Remarkably, we derive a bound showing that the degree of such coherence in the state of the elements of the environment represents a resource, which can be consumed to convert heat into an ordered (unitarylike) energy term in the system, even though no work is performed in the global dynamics.
View Article and Find Full Text PDFObjectives: To compare unassisted and CAD-assisted detection and time efficiency of radiologists in reporting lung nodules on CT scans taken from patients with extra-thoracic malignancies using a Cloud-based system.
Materials And Methods: Three radiologists searched for pulmonary nodules in patients with extra-thoracic malignancy who underwent CT (slice thickness/spacing 2 mm/1.7 mm) between September 2015 and March 2016.
Quantum information theory has considerably helped in the understanding of quantum many-body systems. The role of quantum correlations and in particular, bipartite entanglement, has become crucial to characterise, classify and simulate quantum many body systems. Furthermore, the scaling of entanglement has inspired modifications to numerical techniques for the simulation of many-body systems leading to the, now established, area of tensor networks.
View Article and Find Full Text PDFBackground: Follow-up aims to precociously identify recurrences, metastases or treatment-related adverse events so as to undertake the appropriate therapy. Guidelines admit lack of knowledge on optimal surveillance schedule, but suggest follow-up based on experts' opinion and risk stratification. To identify the impact, if any, of regular follow-up, we interrogated our prospectively collected database whether early detection of recurrences affected both clinical management and, likely, the outcome.
View Article and Find Full Text PDFWe study work extraction from the Dicke model achieved using simple unitary cyclic transformations keeping into account both a nonoptimal unitary protocol and the energetic cost of creating the initial state. By analyzing the role of entanglement, we find that highly entangled states can be inefficient for energy storage when considering the energetic cost of creating the state. Such a surprising result holds notwithstanding the fact that the criticality of the model at hand can sensibly improve the extraction of work.
View Article and Find Full Text PDFA double well loaded with bosonic atoms represents an ideal candidate to simulate some of the most interesting aspects in the phenomenology of thermalisation and equilibration. Here we report an exhaustive analysis of the dynamics and steady state properties of such a system locally in contact with different temperature reservoirs. We show that thermalisation only occurs 'accidentally'.
View Article and Find Full Text PDFWe study transitionless quantum driving in an infinite-range many-body system described by the Lipkin-Meshkov-Glick model. Despite the correlation length being always infinite the closing of the gap at the critical point makes the driving Hamiltonian of increasing complexity also in this case. To this aim we develop a hybrid strategy combining a shortcut to adiabaticity and optimal control that allows us to achieve remarkably good performance in suppressing the defect production across the phase transition.
View Article and Find Full Text PDFWe report the experimental reconstruction of the nonequilibrium work probability distribution in a closed quantum system, and the study of the corresponding quantum fluctuation relations. The experiment uses a liquid-state nuclear magnetic resonance platform that offers full control on the preparation and dynamics of the system. Our endeavors enable the characterization of the out-of-equilibrium dynamics of a quantum spin from a finite-time thermodynamics viewpoint.
View Article and Find Full Text PDFBackground: Vertebral metastases are associated with significant pain, disability, and morbidity. Open surgery for fracture stabilization is often inappropriate in this cancer population due to a poor risk-benefit profile, particularly if life expectancy is short. Vertebroplasty and kyphoplasty are appealing adjunctive procedures in patients with malignancy for alleviation of intractable pain.
View Article and Find Full Text PDFPurpose: This study was designed to assess the clinical outcomes of patients treated by vertebral augmentation with nitinol endoprosthesis (VNE) to treat painful vertebral compression fractures.
Methods: Forty patients with one or more painful osteoporotic VCF, confirmed by MRI and accompanied by back-pain unresponsive to a minimum 2 months of conservative medical treatment, underwent VNE at 42 levels. Preoperative and postoperative pain measured with Visual Analog Scale (VAS), disability measured by Oswestry Disability Index (ODI), and vertebral height restoration (measured with 2-dimensional reconstruction CT) were compared at last follow-up (average follow-up 15 months).
Background: Vertebroplasty is a minimally invasive procedure demonstrated to be safe and effective in the treatment of painful osteoporotic and malignancy related fractures when performed in the thoracolumbar spine. Multiple randomized and nonrandomized reports have demonstrated its effectiveness. Conversely, transoral vertebroplasty (TOV) to treat the second cervical vertebra (C2) has been described in only a few case reports.
View Article and Find Full Text PDFPurpose: To assess long-term clinical outcome of percutaneous vertebroplasty (PV).
Materials And Methods: PV was performed in 1,634 patients (1,387 women; median age 73 years ± 9.3) with painful osteoporotic vertebral compression fractures (VCFs).
A case of a 75-year-old patient with a painful pathologic humeral shaft fracture, with unacceptably high surgical risk and unsatisfactory analgesia is reported. In this case, impaired arm function and persistent pain with conservative management resulted in a poor quality of life. Palliation with image-guided percutaneous osteoplasty was considered.
View Article and Find Full Text PDFPurpose: Percutaneous vertebroplasty (PV) is a minimally invasive procedure involving the injection of bone cement within a collapsed vertebral body. Although this procedure was demonstrated to be effective in osteoporosis and metastases, few studies have been reported in cases of multiple myeloma (MM). We prospectively evaluated the safety and efficacy of PV in the treatment of vertebral compression fractures (VCFs) resulting from MM.
View Article and Find Full Text PDFCT colonography (CTC), or virtual colonoscopy, is a non-invasive imaging method that uses CT data sets combined with specialized imaging software to examine the colon. CTC is not used routinely in patients with inflammatory bowel disease (IBD). However, investigating contemporarily the colon, other abdominal organs and the peritoneum with CTC is at times useful in patients with IBD, especially when other diagnostic tools fail.
View Article and Find Full Text PDFSpinor Bose condensates loaded in optical lattices have a rich phase diagram characterized by different magnetic order. Here we apply the density matrix renormalization group to accurately determine the phase diagram for spin-1 bosons loaded on a one-dimensional lattice. The Mott lobes present an even or odd asymmetry associated to the boson filling.
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