Manipulation of photon number-states and its linear optical realization

Akira Kitagawa

Noboru Watanabe

Akira Kitagawa, Katsuji Yamamoto

We analyze the linear optical realization of number-sum Bell measurement and number-state manipulation by taking into account the realistic experimental situation, specifically imperfectness of single-photon detector. The present scheme for number-state manipulation is based on the number-sum Bell measurement, which is implemented with linear optical elements, i.e., beam splitters, phase shifters, and zero-one-photon detectors. Squeezed vacuum states and coherent states are used as optical sources. The linear optical Bell state detector is formulated quantum theoretically with a probability operator measure. Then, the fidelity of manipulation and preparation of number states, particularly for qubits and qutrits, is evaluated in terms of the quantum efficiency and dark count of single-photon detector. It is found that a high fidelity is achievable with small enough squeezing parameters and coherent state amplitudes.

Bellini M., Zavatta A.

Carlo Mereghetti, Beatrice Palano, Simone Cialdi +3 more

This paper uncovers an all-optical implementation of a two state quantum finite automata, whose accepted language would require an unbounded number of states to be accepted on classical finite automata. Our device is based on the polarization of a single photon and its manipulation through linear optical elements.

Akira Kitagawa, Katsuji Yamamoto

We examine various manipulations of photon number states which can be implemented by teleportation technique with number-sum measurement. The preparations of the Einstein-Podolsky-Rosen resources as well as the number-sum measurement resulting in projection to certain Bell state may be done conditionally with linear optical elements, i.e., beam splitters, phase shifters, and zero-one-photon detectors. Squeezed vacuum states are used as primary entanglement resource, while single-photon sources are not required.