Exploring Network-Related Optimization Problems Using Quantum Heuristics

Network-related connectivity optimization problems are underlying a wide range of applications and are also of high computational complexity. We consider studying network optimization problems using two types of quantum heuristics.One is quantum annealing, and the other Quantum Alternating Operator Ansatz, an extension of the Quantum Approximate Optimization Algorithms for gate-model quantum computation, in which a cost-function based unitary and a non-commuting mixing unitary are applied alternately. We present problem mappings for problems of finding the spanning-tree or spanning-graph of a graph that optimizes certain costs, and a variant that further requires the spanning-tree be degree-bounded. With quantum annealing, all constraints are cast into penalty terms in the cost Hamiltonian, and the solution is encoded as the ground state of the Hamiltonian. We provide three mappings to the quadratic unconstrained binary optimization (QUBO) form, compare the resource requirements, and analyze the tradeoffs. For QAOA, we give special focus on the design of mixers based on the constraints presented in the problem, such that the system evolution remains in a subspace of the full Hilbert space where all constraints are satisfied. In the spanning-tree problem, one such hard constraint is that a mixer applied to a spanning-tree needs also be a spanning tree. This involves checking the connectivity of a subgraph, which is a global condition common for most network-related problems. We show how this feature can be efficiently represented in the mixer in a quantum coherent way, based on manipulation of a descendant-matrix and an adjacent matrix. We further develop a mixer for the spanning-graphs based on the spanning-tree mixer

Parallel Longest Common SubSequence Analysis In Chapel

One of the most critical problems in the field of string algorithms is the longest common subsequence problem (LCS). The problem is NP-hard for an arbitrary number of strings but can be solved in polynomial time for a fixed number of strings. In this paper, we select a typical parallel LCS algorithm and integrate it into our large-scale string analysis algorithm library to support different types of large string analysis. Specifically, we take advantage of the high-level parallel language, Chapel, to integrate Lu and Liu's parallel LCS algorithm into Arkouda, an open-source framework. Through Arkouda, data scientists can easily handle large string analytics on the back-end high-performance computing resources from the front-end Python interface. The Chapel-enabled parallel LCS algorithm can identify the longest common subsequences of two strings, and experimental results are given to show how the number of parallel resources and the length of input strings can affect the algorithm's performance.Comment: The 27th Annual IEEE High Performance Extreme Computing Conference (HPEC), Virtual, September 25-29, 202

Duodenal perforation due to a kink in a nasojejunal feeding tube in a patient with severe acute pancreatitis: a case report

<p>Abstract</p> <p>Introduction</p> <p>Nasojejunal feeding tube placement can be achieved by fluoroscopic or endoscopic techniques. Significant complications due to nasojejunal feeding tube placement, such as hydrothorax, duodenal perforation and retroperitoneal emphysema, are very rare. We present a case of massive retroperitoneal emphysema and abscess because of duodenal perforation caused by a kink in a nasojejunal feeding tube.</p> <p>Case presentation</p> <p>A 34-year-old Chinese woman was admitted to our intensive care unit due to hypertriglyceridemia and severe acute pancreatitis. As she suffered from acute respiratory distress syndrome and required mechanical ventilation, a nasojejunal feeding tube was placed by transnasal endoscopic technique. The procedure took place at her bedside. Half a month later, she had a high fever and abdominal distension. An abdominal radiography was performed and showed that the nasojejunal feeding tube was kinking on the third portion of the duodenum and the tip of the nasojejunal feeding tube was inserted into the right retroperitoneum on the second portion of the duodenum.</p> <p>Conclusion</p> <p>When a nasojejunal feeding tube is placed through the transnasal endoscopic technique, an abdominal radiography should be used to confirm the tube's position and indicate if it is kinking or beyond the ligament of Treitz.</p