Maximal success probabilities of linear-optical quantum gates
نویسندگان
چکیده
Numerical optimization is used to design linear-optical devices that implement a desired quantum gate with perfect fidelity, while maximizing the success rate. For the two-qubit controlled-sign or controlled NOT CNOT gate, we provide numerical evidence that the maximum success rate is S=2 /27 using two unentangled ancilla resources; interestingly, additional ancilla resources do not increase the success rate. For the three-qubit Toffoli gate, we show that perfect fidelity is obtained with only three unentangled ancilla photons—less than in any existing scheme—with a maximum S=0.003 40. This compares well to S= 2 /27 2 /2 0.002 74, obtainable by combining two CNOT gates and a passive quantum filter T. C. Ralph, K. J. Resch, and A. Gilchrist, Phys. Rev. A 75, 022313 2007 . The general optimization approach can easily be applied to other areas of interest, such as quantum error correction, cryptography, and metrology M. M. Wilde and D. B. Uskov, Phys. Rev. A 79, 022305 2009 ; G. A. Durkin and J. P. Dowling, Phys. Rev. Lett. 99, 070801 2007 .
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