TY - GEN

T1 - Quantum state reconstruction

T2 - Quantum Electronics and Laser Science Conference, QELS 2001

AU - James, D. F.V.

AU - Kwiat, P. G.

AU - Hradil, Z.

AU - Řeháček, J.

AU - White, A. G.

N1 - Publisher Copyright:
© 2001 Optical Soc. Of America.

PY - 2001

Y1 - 2001

N2 - Summary form only given. Experimental techniques for measurement of the quantum state of light have been the subject of intensive investigation for some time. Tomographic techniques have been applied to experiments such as the homodyne measurement of the Wigner function of a single mode of light and of the density matrix of the polarization degrees of freedom of a pair of entangled photons. In this technique, the density matrix (or Wigner function) which characterizes the quantum state of the system being measured is found from a linear transformation of experimental data. There are a number of drawbacks to the method, principally in that the recovered state might not, because of experimental noise, correspond to a physical state. For example, density matrices for any quantum state must be Hermitian, positive semi-definite matrices with unit trace. The tomographically measured matrices often fail to be positive semi-definite. To avoid this problem, the maximum likelihood approach to the estimation of quantum states has been developed. We evaluate two different approaches to the maximum likelihood technique, namely defining the likelihood function f as a weighted sum of squared variances from measured data, and defining it in terms of information content. These are compared with results of standard tomographical schemes.

AB - Summary form only given. Experimental techniques for measurement of the quantum state of light have been the subject of intensive investigation for some time. Tomographic techniques have been applied to experiments such as the homodyne measurement of the Wigner function of a single mode of light and of the density matrix of the polarization degrees of freedom of a pair of entangled photons. In this technique, the density matrix (or Wigner function) which characterizes the quantum state of the system being measured is found from a linear transformation of experimental data. There are a number of drawbacks to the method, principally in that the recovered state might not, because of experimental noise, correspond to a physical state. For example, density matrices for any quantum state must be Hermitian, positive semi-definite matrices with unit trace. The tomographically measured matrices often fail to be positive semi-definite. To avoid this problem, the maximum likelihood approach to the estimation of quantum states has been developed. We evaluate two different approaches to the maximum likelihood technique, namely defining the likelihood function f as a weighted sum of squared variances from measured data, and defining it in terms of information content. These are compared with results of standard tomographical schemes.

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U2 - 10.1109/QELS.2001.962166

DO - 10.1109/QELS.2001.962166

M3 - Conference contribution

AN - SCOPUS:84958245025

T3 - Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001

SP - 238

BT - Technical Digest - Summaries of Papers Presented at the Quantum Electronics and Laser Science Conference, QELS 2001

PB - Institute of Electrical and Electronics Engineers Inc.

Y2 - 6 May 2001 through 11 May 2001

ER -