|
| related topics |
| {states, state, optimal} |
| {let, theorem, proof} |
| {operator, operators, space} |
| {information, entropy, channel} |
| {qubit, qubits, gate} |
| {cos, sin, state} |
| {group, space, representation} |
|
Unital quantum operators on the Bloch ball and Bloch region
P. S. Bourdon, H. T. Williams
abstract: For one qubit systems, we present a short, elementary argument characterizing
unital quantum operators in terms of their action on Bloch vectors. We then
show how our approach generalizes to multi-qubit systems, obtaining
inequalities that govern when a ``diagonal'' superoperator on the Bloch region
is a quantum operator. These inequalities are the n-qubit analogue of the
Algoet-Fujiwara conditions. Our work is facilitated by an analysis of
operator-sum decompositions in which negative summands are allowed.
- oai_identifier:
- oai:arXiv.org:quant-ph/0308089
- categories:
- quant-ph
- comments:
- Revised and corrected, to appear in Physical Review A
- doi:
- 10.1103/PhysRevA.69.022314
- arxiv_id:
- quant-ph/0308089
- created:
- 2003-08-16
- updated:
- 2003-12-13
Full article ▸
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