Excursions at the Interface of Topological Phases of Matter and Quantum Error Correction

Topological quantum error-correcting codes are a family of stabilizer codes that are built using a lattice of qubits covering some manifold. The stabilizers of the code are local with respect to the underlying lattice, and logical information is encoded in the non-local degrees of freedom. The locality of stabilizers in these codes makes them especially suitable for experiments. From the condensed matter perspective, their code space corresponds to the ground state subspace of a local Hamiltonian belonging to a non-trivial topological phase of matter. The stabilizers of the code correspond to the Hamiltonian terms, and errors can be thought of as excitations above the ground state subspace. Conversely, one can use fixed point Hamiltonian of a topological phase of matter to define a topological quantum error-correcting code.This close connection has motivated numerous studies which utilize insights from one view- point to address questions in the other. This thesis further explores the possibilities in this di- rection. In the first two chapters, we present novel schemes to implement logical gates, which are motivated by viewing topological quantum error-correcting codes as topological phases of matter. In the third chapter, we show how the quantum error correction perspective could be used to realize robust topological entanglement phases in monitored random quantum circuits. And in the last chapter, we explore the possibility of extending this connection beyond topological quan- tum error-correcting codes. In particular, we introduce an order parameter for detecting k-local non-trivial states, which can be thought of as a generalization of topological states that includes codewords of any quantum error-correcting code

Evaluation of Early Removal of Urinary Catheter after Rectal Cancer Surgery

Background: It is a common practice to catheterize the bladder during major surgical procedure and leave the catheter in situ to avoid post-operative urinary complications such as retention or incontinence. Catheter removal on post-operative day 5 is a routine, and it causes some urinary problems and longer hospital stay. The objective of this study was to evaluate the effect of early removal of urinary catheter on the 1st day after rectal cancer surgery, on the rate of urinary complications.Methods: This quasi-experimental study was approved by the Ethics Committee of Shahid Beheshti University of Medical Sciences, Iran. 80 patients with rectal cancer underwent surgery at Imam Hossein Hospital from 2015 to 2016, were recruited with planned early removal of urinary catheter after surgery. Personal and disease information was recorded in all patients after obtaining the informed consent. Urinary complications were checked by the surgical resident after the operation.Results: Mean age of participants was 56.64 ± 14.90 (range: 22-84 years). From these patients 46 (57.5%) were male, and 34 (42.5%) were female. Two cases (2.5%) were manifested urinary problems in men. One of them reported urinary retention and the other one had hematuria. Both patients were in Stage III of rectal cancer and had laparoscopic surgery. Urinary incontinence was not reported in any patients.Conclusions: In patients who undergoing rectal cancer surgery, urinary catheter can be removed on the 1st post-operative day without any significant increase in urinary complications