Dominik Janzing, Thomas Beth. -1 for a black-box unitary transformation U. Quantum Information & Computation, 2(3):192-197, 2002. [doi]
@article{JanzingB02, title = {-1 for a black-box unitary transformation U}, author = {Dominik Janzing and Thomas Beth}, year = {2002}, url = {http://portal.acm.org/citation.cfm?id=2011432}, researchr = {https://researchr.org/publication/JanzingB02}, cites = {0}, citedby = {0}, journal = {Quantum Information & Computation}, volume = {2}, number = {3}, pages = {192-197}, }