Pande, Varad R.2020-03-052020-03-052020-01-02Pande, Varad R.; Optimal Entropy Compression and Purification in Quantum Bits; Quantum Physics (2020); https://arxiv.org/abs/2001.00562http://hdl.handle.net/11603/17496Global unitary transformations (optswaps) that optimally increase the bias of any mixed computation qubit in a quantum system - represented by a diagonal density matrix - towards a particular state of the computational basis which, in effect, increases its purity are presented. Quantum circuits that achieve this by implementing the above data compression technique - a generalization of the 3B-Comp [Fernandez, Lloyd, Mor, Roychowdhury (2004); arXiv: quant-ph/0401135] used before are described. These circuits enable purity increment in the computation qubit by maximally transferring part of its von Neumann or Shannon entropy to any number of surrounding qubits and are valid for the complete range of initial biases. Using the optswaps, a practicable new method that algorithmically achieves hierarchy-dependent cooling of qubits to their respective limits in an engineered quantum register opened to the heat-bath in delineated. In addition to multi-qubit purification and satisfying two of DiVincenzo's criteria for quantum computation in some architectures, the implications of this work for quantum data compression are discussed.13 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.Text