22 research outputs found
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Algorithms and Architectures for Quantum Simulation with Neutral-atom Arrays
No full textFast and scalable quantum simulations promise to revolutionize our understanding of complex quantum systems,
In this thesis, we primarily aim to develop algorithms and architectures for leveraging programmable quantum devices, to model complex physical phenomena. As quantum computers can natively capture superposition and entanglement, two key attributes which are challenging for classical computers to accurately model, this approach promises significant benefits in the long run.
We focus primarily on neutral-atom arrays, an emerging experimental platform, although many of our results apply more generally as well. The work is structured into three phases, each progressively advancing the complexity and control of considered experimental hardware, and in parallel the importance and applicability of the considered quantum simulations.
In the first phase (Chapters 1–3), we address the challenge of programming and controlling quantum many-body systems through analog techniques. Analog quantum simulation utilizes continuous control parameters to engineer desired quantum states and dynamics. Chapter 1 introduces novel methods for steering entanglement using quantum many-body scars, harnessing special strongly-interacting dynamics to manipulate quantum entanglement robustly. Chapter 2 advances this approach by showing how Floquet engineering can be used to systematically generate interactions, and how this enables sophisticated control over entanglement and access to novel quantum phases. Chapter 3 integrates these developments into a general framework for programming Hamiltonians into analog quantum simulators with time-reversal capabilities, illustrating the power of programmable analog strategies for simulations of lattice gauge theories.
The second phase (Chapters 4–6) shifts focus to topologically ordered quantum states, known for their exotic long-range entanglement and fundamental significance in condensed matter physics and quantum computation. Chapter 4 presents strategies to enhance the experimental detection and verification of topological order using ideas from the renormalization group. The procedure we develop, order parameters dressed by local quantum error correction, significantly improve the practical observability of these delicate quantum phases. In Chapters 5 and 6, we explore novel techniques for realizing topological phases, by exploiting newly developed experimental capabilities, notably atom reconfiguration, to achieve precise digital control. In particular, we show how to engineer chiral Floquet spin liquids - exotic quantum phases exhibiting robust quantum coherence and non-Abelian excitations — as well as simulations of topological fermionic matter. These advancements not only illuminate foundational physics but also bridge towards robust quantum error correction schemes.
The final phase (Chapters 7 and 8) expands the techniques developed thus far towards the simulation of increasingly complex physical systems relevant to chemistry and materials science. Chapter 7 discusses a general framework for digital quantum simulation of effective spin models, prevalent in condensed matter physics, introducing crucial techniques for engineering and characterizing these Hamiltonians. Chapter 8 extends these insights by proving that fermionic quantum systems, essential for realistic simulations of electronic structures in molecules and materials, can be efficiently encoded into qubits. This advance significantly reduces computational complexity and opens pathways for genuine quantum simulations of chemical systems.
Collectively, these contributions represent substantial progress towards practical quantum simulation with neutral-atom quantum processors, laying critical foundations for future applications in physics, chemistry, and quantum information science.Physic
Novel mutation in the RNASEH1 gene in a chronic progressive external ophthalmoplegia patient
No full textSynthesis of SWNT/Pt nanocomposites for their effective role in hydrogen storage applications
No full textTotal Anterior Staphyloma Secondary to Acanthamoeba Keratitis.
No full textABSTRACT
There are very few published cases of total anterior staphyloma, all of which have been reported as secondary to fungal keratitis. This study reports the clinical and histopathological findings and subsequent management of a 27-year-old healthy female patient who developed total anterior staphyloma after poor compliance with treatment for clinically diagnosed acanthamoeba keratitis. She underwent a successful evisceration with good long-term results. This case highlights that total anterior staphyloma may also result from untreated keratitis which is not fungal in origin. In cases of fungal and acanthamoeba keratitis, patient compliance with both treatment and follow-up is paramount to avoid vision-threatening sequelae that present significant challenges in their management
CO2-dependent opening of connexin 26 and related beta connexins
No full textWe have previously shown connexin mediated CO2-dependent ATP release from the surface of the medulla oblongata. Given the localization of connexin 26 (Cx26) to the chemosensing areas of the medulla, we have tested in a heterologous expression system (HeLa cells) whether Cx26 may be sensitive to changes in P-CO2. Cx26 responded to an increase in P-CO2 at constant extracellular pH by opening and to a decrease in P-CO2 by closing. Furthermore, Cx26 was partially activated at a physiological P-CO2 of around 40 mmHg. Cx26 in isolated patches responded to changes in P-CO2, suggesting direct CO2 sensitivity of the hemichannel to CO2. Heterologous expression of Cx26 in HeLa cells was sufficient to endow them with the capacity to release ATP in a CO2-sensitive manner. We have examined other heterologously expressed connexins for their ability to respond to changes in P-CO2. The closely related beta connexins Cx30 and Cx32 also displayed sensitivity to changes in P-CO2, but with slightly different characteristics from Cx26. The more distant Cx43 exhibited CO2-dependent closing (possibly mediated through intracellular acidification), while Cx36 displayed no CO2 sensitivity. These surprising findings suggest that connexins may play a hitherto unappreciated variety of signalling roles, and that Cx26 and related beta connexins may impart direct sensitivity to CO2 throughout the brain
NUCLEAR DETERRENCE AND NORTH KOREA―DISSUASION OR PERSUASION?
No full textThe threat of nuclear war has been a possibility since the first atomic device was invented during World War II. From the end of World War II through the Cold War period, the greatest risk of nuclear proliferation was between the main superpowers at the time, the United States and the Soviet Union. U.S. nuclear deterrence doctrine promised mutually assured destruction (MAD): if the Soviets were to launch a nuclear missile at the United States, the United States would retaliate in such a way to ensure the annihilation of the Soviet Union.
The global economic, social, and political environment has changed since the end of the Cold War; however, the threat of atomic warfare still exists with the emergence of the Democratic People’s Republic of North Korea as a nuclear threat. This thesis explores the question of whether the doctrine developed during the Cold War is still valid: Is the U.S. nuclear strategy sufficient to deter North Korea from attacking the United States and its allies in the East Asian region? In formulating an answer to the question, the author analyzed the motivations, perceptions, and intentions of North Korea’s regime from the country’s formation to present day. While it is clear that the original Cold War MAD doctrine will not work for North Korea, it is recommended that the right combination of MAD elements, conventional forces, UN sanctions, and negotiations will provide a chance for the denuclearization of the Korean Peninsula to become a reality.Approved for public release; distribution is unlimited.Civilian, Department of Homeland Securityhttp://archive.org/details/nucleardeterrenc109456408
Religious Syncretism and Literary Innovation. New Perspectives on Bhakti and Rasas in the Vijñānagītā by Keshavdas
No full textThe Vijñānagītā (1610) is one of the last works composed by Keśavadāsa. As a work of his old age, growing apart from Rīti mannerism and courtly themes, it seems to answer to the author’s enquiry for spirituality and religious desire. The author’s literary concern is expressed in the framework of the allegory, which represents a structural device enriching the potentiality of poetic significance. The Vijñānagītā is one of the many Hindi adaptations of the Prabodhacandrodaya by Kṛṣṇamiśra, enriched with many philosophical and religious hints coming from different religious traditions. Giving up any mere translation of the Sanskrit text, the author inserts the classical allegoric drama about the war between Mahāmoha and Viveka within the religious and cultural context of the early Seventeenth century north India. The story becomes a pretext to compose a compendium of philosophy extending from classical purāṇic lore, to treatises on moral, up to the popular attitude for devotion in later Vaishavism. Some interesting influences of Bhakti can be traced out in the many quotations taken from the most disparate works, such as Yogavāśiṣṭa. Purāṇas, Rāmāyaṇa up to the Nāṭyaśāstra, allowing hypothesizing some relationship with the concepts of rasas belonging to classical aesthetics applied to the metaphysics of devotion. Dealing with a concept already theorized by Caitanya and well-known in some Vaishnava circles, he interprets the theory of aesthetic emotions in the new context of devotionalism, allowing tracing some connections between the Rīti poetry developed in the literary setting of courts and the popular Bhakti tradition, which so far had always been considered as detached from it, on the basis of different intents and expressive techniques
Visualizing the optical field strengths in Au/dielectric nanostructures and its correlation to SERS enhancements
No full textRole of legislature in the democratization process in Malawi
No full textAmong the many countries that underwent the democratization process in Africa in the mid-1990s, Malawi remains in the transition process while struggling to fully consolidate. Its parliament faces challenges impacting its performance of the core functions: executive oversight, constituency service and legislation. Despite the challenges the Malawi parliament faces, it distinguished itself in 2002 when it helped to maintain constitutionality by denying the president's bid to change the constitution to allow him to stand beyond the constitutional limit of two terms. Since then, the parliament has been less effective in performing its main functions. This thesis compares the parliament's performance of its core functions in the periods 1994-2004 and 2004-2009 to explain why its performance declined over time. It finds that the struggle for control of the House undermined the parliament's ability to perform these key functions, and thereby weakened the democratization process.Approved for public release; distribution is unlimited.Malawi Defence Force author updated aq 04/13/2011.http://archive.org/details/roleoflegislatur10945506
Fermionic Hamiltonians without trivial low-energy states
No full textOne of the main problems in computational physics is predicting the low-energy behavior of many-body quantum systems. The computational complexity of this problem, however, is relatively poorly understood. A recent major progress in this direction has been the no low-energy trivial states (NLTS) theorem; it gives a family of qubit Hamiltonians whose low-energy states cannot be reached by shallow quantum circuits. In this work we provide a fermionic counterpart to this theorem, constructing local fermionic Hamiltonians with no low-energy trivial states. Distinct from the qubit case, we define trivial states via finite-depth fermionic quantum circuits. We further strengthen the result, allowing free access to (generally, deep) Gaussian fermionic circuits into our notion of a trivial state. The desired fermionic Hamiltonian can be constructed using any qubit Hamiltonian which has the NLTS property via well-spread distributions over bitstrings. We also define a fermionic analog of quantum probabilistically checkable proofs (PCPs) and explore the relation of fermionic PCP class with the qubit version
