Simulating quantum operations with mixed environments
Abstract
We study the physical quantum resources required to implement general quantum operations, and provide bounds on the minimum possible size which an environment must be in order to perform certain quantum operations. We prove that contrary to a previous conjecture, not all quantum operations on a single qubit can be implemented with a singlequbit environment, even if that environment is initially prepared in a mixed state. We show that a mixed singlequtrit environment is sufficient to implement a special class of operations, the generalized depolarizing channels.
 Publication:

Physical Review A
 Pub Date:
 August 1999
 DOI:
 10.1103/PhysRevA.60.881
 arXiv:
 arXiv:quantph/9806095
 Bibcode:
 1999PhRvA..60..881T
 Keywords:

 03.67.a;
 02.70.c;
 89.70.+c;
 89.80.+h;
 Quantum information;
 Computational techniques;
 simulations;
 Information theory and communication theory;
 Quantum Physics
 EPrint:
 4 pages Revtex + 1 fig, pictures at http://stout.physics.ucla.edu/~smolin/tetrahedron .Several small corrections