1. Tomographic characterization of a linear optical quantum Toffoli gate.
- Author
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Mičuda, M., Miková, M., Straka, I., Sedlák, M., Dušek, M., Ježek, M., and Fiurášek, J.
- Subjects
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OPTICAL quantum computing , *QUBITS , *POLARIZED photons , *INTERFEROMETERS , *CALCITE - Abstract
We report on a detailed characterization of a three-qubit linear optical quantum Toffoli gate. Our experiment utilizes correlated photon pairs generated in the process of spontaneous parametric down-conversion. Two qubits are encoded into polarization and spatial degrees of freedom of a signal photon, and the third qubit is represented by polarization of an idler photon. The linear optical Toffoli gate is implemented by interference of photons on a partially polarizing beam splitter inserted inside a Mach Zehnder interferometer formed by two calcite beam displacers. We have measured 4032 different two-photon coincidences, which allows us to estimate the fidelity of the gate to be 90%. Although these data are not tomographically complete, we show that they are sufficient for a reliable reconstruction of the quantum process matrix of the gate via the recently proposed maximum likelihood-maximum entropy estimation procedure. To probe the entangling capability of the gate, we have investigated generation of three-qubit GHZ states from fully and partially separable input states and we have performed a full tomography of the output states. We compare the reconstructed states with theoretical predictions obtained with the use of the estimated quantum process matrix and obtain a very good agreement. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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