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Manuscript Title: SQSIMUL: a Fortran code for the computation of squeezing properties and photon statistics in multiphoton processes.
Authors: F.J. Bermejo, J. Santoro, L. Sainz de los Terreros
Program title: SQSIMUL
Catalogue identifier: AATE_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 43(1987)245
Programming language: Fortran.
Computer: SPERRY UNIVAC 1100/80.
Operating system: EXEC-8, LEVEL 38R5B.
RAM: 64K words
Word size: 72
Keywords: Laser physics, Quantum optics, Squeezed single-mode, States.
Classification: 15.

Nature of problem:
The program calculates time dependent diagonal and off-diagonal matrix elements for the reduced density operator of a single-mode radiation field undergoing multiphoton absorption or emission process by an irreversible Markovian interaction with two-level atomic media. By means of these distributions a complete analysis of quantum noise fluctuations as well as second and higher-order squeezing properties of the photon field may be realized for arbitrarily chosen coherent or squeezed input field.

Solution method:
The method essentially consists in integration of the master equation for the time evolution of the field statistics in the photon-number representation. The numerical model implies a truncation of the infinite series by which the statistical averages are calculated. The ordinary eigenvalue method is used for the nonlinear multiphoton processes (two and higher order photon processes) whereas direct expotentiation of the matrix of the differential system involved is used for the linear one-photon counterpart.

Restrictions:
In order to produce satisfactory results, the input mean photon numbers should be kept within the range 0<= n0<= 75. The maximum degree of squeezing should not be greater than 10.

Running time:
The test runs comprising 20 time steps and 120-point distribution took 25 secs. on the UNIVAC 1100/80.