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Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE

Quantum tomography of the optical four level states

S. P. Kulik, Gleb Maslennikov, Ekaterina V. Moreva, Stanislav S. Straupe

Published Mar 3, 2006• 1 citation
Publisher

Abstract

We discuss a procedure of measurement of an arbitrary quantum state of an optical system in Hilbert space with the dimension d=4. Such states can be realized using a collinear frequency-nondegenerate regime of spontaneous parametric down-conversion. The method has been tested for a number of polarization states of a biphoton field. A high accuracy of the reconstruction of the states (above 99%) indicates that the procedures proposed for reconstructing the quantum state of the system are adequate.

DOI
10.1117/12.674976

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We discuss a procedure of measurement of an arbitrary quantum state of an optical system in Hilbert space with the dimension d=4. Such states can be realized using a collinear frequency-nondegenerate regime of spontaneous parametric down-conversion. The method has been tested for a number of polarization states of a biphoton field. A high accuracy of the reconstruction of the states (above 99%) indicates that the procedures proposed for reconstructing the quantum state of the system are adequate.
A method for reconstructing an arbitrary quantum state of an optical system in Hilbert space with dimension d = 4 is discussed. Such states can be realized using a collinear frequency-nondegenerate regime of generating spontaneous parametric down-conversion. The method has been tested for a number of polarization states of a biphoton field. The high accuracy of the reconstruction of the states (above 99%) indicates that the procedures proposed for reconstructing the quantum state of the system are adequate.
The physical principles of a quantum key distribution protocol using four-level optical systems are discussed. Quantum information is encoded into polarization states created by frequency-nondegenerate spontaneous parametric down-conversion in collinear geometry. In the scheme under analysis, the required nonorthogonal states are generated in a single nonlinear crystal. All states in the selected basis are measured deterministically. The results of initial experiments on transformation of the basis polarization states of a four-level optical system are discussed.
We present the experimental approach to the determination of the Fock-States density matrix via the optical homodyne tomography. The single photon state is generated by Spontaneous Parametric Down Conversion (SPDC) in a nonlinear crystal pumped by the Second Harmonic of a picosecond dye laser. The fundamental frequency of the dye-laser realizes the local oscillator for the homodyne measurement. In this paper we describe the experimental apparatus and discuss the possibility to realize the quantum tomography of the single-photon state and, in the future, of the n-photon state. The experimental determination of the field state prepared in a coherent state with different mean photon numbers is also presented.