By virtue of the coherent state representation and the operator ordering method we find a new approach for transiting Hermite polynomials to Laguerre polynomials. We also derive the new reciprocal relation of Laguerre polynomials ∑n=0 （-1）n （n^l）Ln （x） = x^l/n, n-O and its application in deriving the sum rule of the Wingner function of Fock states is demonstrated. Some new expansion identities about the operator Laguerre polynomial are also derived. This opens a new route of deriving mathematical polynomials formulas by virtute of the quantum mechanical representations and operator ordering technique.
A general framework applicable to deriving the s-ordered operator expansions is presented in this paper.We firstly deduce the s-ordered operator expansion formula of density operator ρ a?,a and introduce the technique of integration within the sordered product of operators (IWSOP).Based on the deduction and the technique,we derive the s-ordered expansions of operators (μX + νP)n and Hn (μX + νP) (linear combinations of the coordinate operator X and the momentum operator P,Hn (x) is Hermite polynomial),respectively,and discuss some special cases of s=1,0,-1.Some new useful operator identities are obtained as well.
We investigate the photon number distribution of squeezed chaotic field(SCF)(a mixed state),by converting the density operator of SCF into its normally ordered bivariate distribution form we find that it is a Legendre distribution.This is a remarkable result.
For classical Hamiltonian with general form H = 1/2∑ijMijpipj＋1/2∑ijLijqiqj we find a new convenient way to obtain its normal coordinates, namely, let H be quantised and then employ the invariant eigen-operator （IEO） method （Fan et al. 2004 Phys. Lett. A 321 75） to derive them. The general matrix equation, which relies on M and L, for obtaining the normal coordinates of H is derived.
We construct a new type of photon-subtracted squeezed coherent state (PSSCS) based on a squeezed coherent state (SCS) [Phys.Lett.A 220 (1996)81].Some of the statistical properties of the PSSCS,such as Mandel's Q parameter and photon-number distribution,are investigated and the corresponding non-classicality is discussed.
