The expansion of operators as ordered power series in the annihilation and creation operators
a and ${a}^{\ifmmode\dagger\else\textdagger\fi{}}$ is examined. It is found that normally ordered power series exist and converge quite generally, but that for the case of antinormal ordering the required
c-number coefficients are infinite for important classes of operators. A parametric ordering convention is introduced according to which normal, symmetric, and antinormal ordering correspond to the values $s=+1,0,\ensuremath{-}1$, respectively, of an order parameter
s. In terms of this convention it is shown that for bounded operators the coefficients are finite when
s>0, and the series are convergent when
s>21. For each value of the order parameter
s, a correspondence between operators and
c-number functions is defined. Each correspondence is one-to-one and has the property that the function $f(\ensuremath{\alpha})$ associated with a given operator
F is the one which results when the operators
a and ${a}^{\ifmmode\dagger\else\textdagger\fi{}}$ occurring in the ordered power series for
F are replaced by their complex eigenvalues $\ensuremath{\alpha}$ and ${\ensuremath{\alpha}}^{*}$. The correspondence which is realized for symmetric ordering is the Weyl correspondence. The operators associated by each correspondence with the set of $\ensuremath{\delta}$ functions on the complex plane are discussed in detail. They are shown to furnish, for each ordering, an operator basis for an integral representation for arbitrary operators. The weight functions in these representations are simply the functions that correspond to the operators being expanded. The representation distinguished by antinormal ordering expresses operators as integrals of projection operators upon the coherent states, which is the form taken by the
P representation for the particular case of the density operator. The properties of the full set of representations are discussed and are shown to vary markedly with the order parameter
s.
We develop a star-product scheme of symbols defined by the normally ordered powers of the creation and annihilation photon operators, . The corresponding phase space is a two-dimensional lattice with nodes ( m , n ) given by pairs of non-negative integers. The star-product kernel of symbols on the lattice and intertwining kernels to other schemes are found in an explicit form. Analysis of peculiar properties of the star-product kernel results in new sum relations for factorials. Advantages of the developed star-product scheme for describing dynamics of quantum systems are discussed and time evolution equations in terms of the ordered moments are derived.
Two calculation formulas of expansion each other for normal ordering and antinormal ordering of creation operator and annihilation operator are given in this paper as () n( +) m=∑pk=0m!n!(m-k)!(n-k)!k!( +) m-k () n-k and ( +) n() m=∑pk=0(-1) km!n!(m-k)!(n-k)!k!() m-k ( +) n-k , where p=min(n,m). It is right that we prove by using mathematical inductive method. The two formulas of this paper are used in a wide class of study of quantum statistical properties for various excited optical fields.
The recent development of experimental techniques to implement the creation and the annihilation operators in the optical domain has found great interest for quantum information manipulation and processing. Quantum states of light obtained by the application of alternated sequences of the creation and annihilation operators
a^† and
a^ to a thermal state of light depend on the order in which the two operations are performed. The non-commutativity of the bosonic operators,
a^a^†=a^†a^=1, has been experimentally verified in terms of density matrixes and Wigner functions, which are reconstructed by quantum homodyne tomography. Recently, a setup has been proposed to directly and completely prove the bosonic commutation relation where a single-photon interferometer is used to create coherent superpositions of two alternated sequences of operators, such as
[a^a^†±a^†a^]. Some of the latest experimental results are discussed.
In this paper by virtue of the technique of integration within an ordered product (IWOP) of operators and the intermediate coordinate-momentum representation in quantum optics, we derive the normal ordering and antinormal ordering products of the operator ( fQ + gP ) n when n is an arbitrary integer. These products are very useful in calculating their matrix elements and expectation values and obtaining some useful mathematical formulae. Finally, the applications of some new identities are given.
A new integral representation is obtained for the star product corresponding to the s -ordering of the creation and annihilation operators. This parametric ordering convention introduced by Cahill and Glauber enables one to vary the type of ordering in a continuous way from normal order to antinormal order. Our derivation of the corresponding integral representation is based on using reproducing formulas for analytic and antianalytic functions. We also discuss a different representation whose kernel is a generalized function and compare the properties of this kernel with those of the kernels of another family of star products which are intermediate between the - and pq -quantization.