CQuIC Seminars
Limitations in quantum extension ("joinability") problems: quantum states vs. channels
Presented by Peter Johnson, Dartmouth College
Quantum kinematics and quantum dynamics are constrained by positive-semidefiniteness and complete positivity, respectively. These rules play a crucial role in quantum information tasks, as they enforce no-cloning (no-broadcasting) as well as monogamy of entanglement. A quantum joinability problem embodies a generalization of such limitations, asking whether a given list of reduced states (or channels) are consistent with any valid global state (or channel). We investigate the connection between joinability problems for bipartite quantum states and for quantum channels. In the case of bipartite operators, with collective unitary invariance (Werner states and depolarizing channels), we analytically determine the limitations on joinability, and compare to limitations of purely classical nature. We find that a certain "parity difference" between the set of quantum states and the set of quantum channels explains the contrast in the respective joinability limitations in certain cases.
10:00 am, Thursday, May 8, 2014
PAIS-2540, PAIS
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