Micro Electronic and Mechanical Systems 2009 Part 15 pot

Neuron Network Applied to Video Encoder 481 Fig Basic component of neural network Dendrites are inputs into neuron Natural neurons have even hundreds of inputs Point where dendrites are touching the neuron is called a synapse Synapse is characterized by effectiveness, called synaptic weight Neuron output is formed in a following way: signals on dendrites are multiplied by corresponding synaptic weights, results are added and if they exceed threshold level on the result is applied a transfer function of neuron, which is marked f on a figure Only limitation of transfer function is that it must be limited and nondecreasing Neuron output is routed to axon, which by its branches transfers result to dendrites In this way, output from one layer of network is transferred to the next one In neural networks, three types of transfer functions are presently being used: • jumping • logical with threshold • sigmoid All three types are shown in figure 4: Fig Three types of transfer functions The neural network has unique multiprocessing architecture and without much modification, it surpasses one or even two processors of von Neumann architecture characterized by serial of sequential information processing (S.P Teeuwsen at all, 2003) It has ability to explain every functional dependence and to expose a nature of such 482 Micro Electronic and Mechanical Systems dependence with no need to external incentives, demands for building a model or its change In short, neural network may be considered as a black box capable of predicting output pattern or a signal after recognizing given input pattern Once trained, it may recognize similarities when a new input signal is given, which results in predicted output signal There are two categories of neural networks: artificial and biological ones Artificial neural networks are in structure, function and in information processing similar to biological ones In computer sciences, neural network is an intertwined network of elements that processes data One of more important characteristics of neural networks is their capability to learn from limited set of examples The neural network is a system comprised of several simple processors (units, neurons), and every one of them gas its local memory where it stores processed data These units are connected by communication channels (connections) Data exchanged by these channels are usually numerical ones Units are processing only their local data and inputs obtained directly through connection Limitations of local operators may be removed during training A large number of neural networks created as models of biological neural networks Historically speaking, inspiration for development of neural networks was in desire to construct an artificial system capable of refined, maybe even "intelligent" computations in a way similar to that in human brain Potentially, neural networks are offering us a possibility to understand functioning of human brain Artificial neural networks are a collection of mathematical models that simulate some of observed capabilities in biological neural systems and has similarities to adaptable biological learning They are made of large number of interconnected neurons (processing elements) which are, similarly to biological neurons, connected by their connections comprising of permeability (weight) coefficients, whose role is similar to synapses Most of neural networks have some kind of rule for "training", which adjusts coefficients of inter-neural connections based on input data (Cao J, at all 2003) Large potential of neural networks lays in possibility of parallel data processing, to compute components independent from each other Neural networks are systems made of several simple elements (neurons) that process data parallely There are numerous problems in science and engineering that demand extracting useful information from certain content For many of those problems, standard techniques as signal processing, shape recognition, system control, artificial intelligence and so on, are not adequate Neural networks are an attempt to solve these problems in a similar way as in human brain Like human brain, neural networks are able to learn from given data; later, when they encounter the same or similar data, they are able to give correct or approximate result Artificial neuron, based on sum input and transfer function, computes output values The following figure shows an artificial neuron: Fig Artificial neuron Neuron Network Applied to Video Encoder 483 The neural network model consists of: • neural transfer function • network topology, i.e a way of interconnecting between neurons, • learning laws According to topology, networks are differing by a number of neural layers Usually each layer receives inputs from previous one, and sends its outputs to the next layer The first neural layer is called input layer, the last one is output layer and other layers are called hidden layers Due to a way of interconnecting between neurons, networks may be divided to recursive and non-recursive ones In recursive neural networks, higher layers return information to lower ones, while in non-recursive ones there is a signal flow only from lower to higher layers Neural networks learn from examples Certainly there must be many examples, often even tens of thousands Essence of a learning process is that it causes corrections in synaptic weights When new input data cause no more changes in these coefficients, it is considered that a network is trained to solve a problem Training may be done in several ways: controlled training, training by grading and self-organization No matter which learning algorithm is used, processes are in essence very similar, consisting from following steps: A set of input data is presented to a network Network processes information and remembers result (this is a step forward) The error value is calculated by subtracting obtained result from the expected one For every node a new synaptic weight is calculated (this is a step back) Synaptic weights are changed, or old ones are left and new ones are remembered On network inputs, a new set of input data is brought to network inputs and steps 1-5 are repeated When all examples are processed, synaptic weights values are updated and if an error is under some expected value the network is considered trained We will consider two training modes: controlled training and self-organization training The back-propagation algorithm is the most popular algorithm for controlled training The basic idea is as follows: random pair of input and output results is chosen Input set of signals is sent to the network by bringing one signal at each input neuron These signals are propagating further through the network, in hidden layers, and after some time a results show on output How has this happened? For every neuron an input value is calculated, in a way we previously explained; signals are multiplied by synaptic weights of corresponding dendrites, they are added and a neuron's transfer function is being applied to obtained value The signal is propagated further through the network in a same way, until it reaches output dendrites Then a transformation is done once again and output values are obtained The next step is to compare signals obtained on output axon branches to expected values for given test example Error value is calculated for every output branch If all errors are equal to zero, there is no need for further training – network is able to perform expected task However, in most cases error will be different from zero Then a modification of synaptic weights of certain nodes is called for Self-organized training is a process where a network finds statistical regularities in a set of input data and automatically develops different behavior regimes depending on input For this type of learning, the Kohonen algorithm is used most often The network has only two neural layers: input and output one Output layer is also called a competitive layer (reason will be explained later) Every input neuron is connected to every 484 Micro Electronic and Mechanical Systems neuron in output layer Neurons in output layer are organized in two-dimensional matrix (Zurada, J M.1992) Multilayer neural network with signal propagation forward is one of often used architectures Within it, signals are propagating only ahead, and neurons are organized in layers Most important properties of multilayer networks with signal propagation forward are given as following theorems: Multilayer network with a single hidden layer may uniformly approximate any real continual function on the finite real axis, with arbitrary precision Multilayer network with two hidden layers may uniformly approximate any real continual function of several arguments, with arbitrary precision Input layer receives data from environment Hidden layer receives outputs of a previous layer (in this case, outputs of input layer) and, depending on sum of input weights, gives output For more complex problems, sometimes is necessary more than one hidden layer Output layer computes, on the basis of weight sum and transfer function, outputs from neural network The following figure shows a neural network with one hidden layer Fig Neural network with one hidden layer and with signal propagation forward In this work, we used Kohonen neural network, which is a self-organizing map of properties, belonging to a class of artificial neural networks with unsupervised training (Kukolj D., Petrov M., 2000) This type of neural network may be observed as topologically organized neural map with strong associations to some parts of biological central nervous system The notion of topological map understands neurons that are spatially organized in Neuron Network Applied to Video Encoder 485 maps that guard, in a certain way, the topology of input space Kohonen neural network is intended for following tasks: • Quantumization of input space • Reduction of output space dimension • Preservation of topology present within structure of input space Kohonen neural network is able to classify input samples-vectors, without need to recognize signals for error Therefore, it belongs to group of artificial neural networks with unsupervised learning In actual use of Kohonen network in algorithm for obstacle avoidance, network is not trained but enhancement neurons are given values calculated in advance Regarding clusterization, if a network may not classify input vector to any output cluster, than it gives data regarding how much the input vector is similar to every of clusters defined in advance Therefore, this paper uses Fuzzy Kohonen neural clusterization network (FKCN) Enhancement of h.263 code properties is attained by generating a prototype codebook, characterized by highly changeable differences in picture blocks Generating codebook is attained by training of self-organizing neural network (Haykin, 1994; Lippmann, 1987; Zurada, 1992) After realization of original training concept (Kukolj and Petrov, 2000), a single-layer neural network is formed Every node of output ANN layers represents a prototype within codebook Coordinates of every and node within network is represented by difficulty synaptic coefficients wi After initialization, the code proceeds in two iterative phases First, closest node for every sample is found, using Euclidean distance, and node coordinates are computed as arithmetic means of coordinates for samples clustered around every node The node balancing procedure is continued by confirmation of following condition: K ' ∑ wi − wi ≤ TSKG , i =1 (1) where TASE is equal to a certain part of present value of average square error (ASE) Variables wi and wi' are synaptic vectors of node and in present and previous code iteration If above condition is not met, this step is repeating, otherwise the procedure is proceeding further In a second step, so-called dead nodes are considered, i.e nodes that have no assigned samples If there are no dead nodes, TASE has very low positive value If dead nodes are existing, value q for pre-defined number of nodes (q photon eigen-vector cannot be normalized We shall now examine whether the components of photon eigen-vector proportional to R1 and R2 can be normalized Those components are: sin kr ; W cos kr Y00 (θ , ϕ ) Ω2 = Y00 (θ , ϕ ) r kr r kr The normalization condition is the following: Ω1 = 2π π W W ∫ dϕ ∫ dθ sin θ Y0, (θ ,ϕ ) = 2 (2.61) ∞ ∫ dr r [J (k ′r ) J (kr ) + J (k ′r ) J (kr )] = 1/ 1/ −1 / −1 / (2.62) ∞ W ∫ dr cos(k − k ′)r = k δ (k − k ′) k ′k It is not difficult to show that: ∞ ∫ dr cos(k − k ′)r = , so that the condition (2.62) becomes meaningless This means that even for l = photon eigen-vector cannot be normalized The last possibility for normalization free photons eigen-vector is so called box quantization method In this method the sphere is substituted by cube enveloping it and cyclic boundary conditions are required: e ikr = e ik ( r + L ) , wherefrom it follows that wave vector is quantized: k= 2π n ; n = 1,2,3, L (2.63) Since k = π/λ, it gives that: L=nλ; n = 1,2,3, (2.64) It is seen that the first harmonic of electromagnetic waves has the wave length equal to the cube edge Photon energy is determined in the standard way: E = ck = h 2π c c n = hν n ; ν = 2π L L (2.65) 504 Micro Electronic and Mechanical Systems This expression for energy is in full accordance with Plank’s hypothesis (Planck, 1901) In the normalization condition (2.62) the following translations has to be used: L δ (k − k ′) → δ nn ⎯n⎯→1 ; ⎯ =m ∞ ∫ dr → ∫ dr = L ; cos(k − k ′) r → kk ′ cos 2π ( n − m) r L L ⎯n⎯→ ⎯ =m 2π 2πn nm L Combining this and (2.62) we obtain that the normalization constant is W = On the 2πn basis of this the normalized photon eigen-vector is given by: 2π ⎞ ⎛ nr ⎟ ⎜ sin L ⎟ ⎜ ⎟ ⎜ 2π nr ⎟ 2π ⎛ ⎞ −1 / ⎜ J / ( nr ) ⎟ n ⎜ Y00 (θ ,ϕ ) r L ⎛ Ω1 ⎞ 1 ⎟ ⎜ L ⎜ ⎟= ⎜ ⎟= 3/ ⎜Ω ⎟ ⎟ ; n = 1,2,3, 2π 2πn ⎜ Y (θ ,ϕ ) r −1 / J ( nr ) ⎟ (2πn ) ⎜ ⎝ 2⎠ 2π ⎟ ⎜ 00 ⎟ ⎜ cos −1 / nr L ⎝ ⎠ ⎟ ⎜ L ⎟ ⎜ 2π ⎜ nr ⎟ ⎟ ⎜ L ⎠ ⎝ (2.66) As it can be seen the analysis of single photon eigen-problem in spherical coordinates has shown it orbital momentum of photon is equal to zero and that the spin S = 1/2 is its unique rotational characteristics (Yao, et al., 2005) Physically it is fully understandable that orbital momentum of a free photon is equal to zero since it moves along the straight line On straight line photon radius-vector r and its momentum p = m f r are parallel and this gives that l = r × p = Free photon as a system with complex internal dynamics In the second part of this work the free photon Hamiltonian will be linearized using Pauli’s matrices Based on the correspondence of Pauli matrices kinematics and the kinematics of spin operators, the unitary transformation of this form (equivalent Hamiltonian), will be analyzed by the method of Green’s functions Since photon is relativistic quantum object the exact determining of its characteristics is impossible It is the reason for series of experimental works in which photon orbital momentum, which is not integral of motion, will be theoretically investigated 3.1 Introduction The fact that photon Hamiltonian is not a linear operator has a set of consequences that have not been studied sufficiently so far The main reason is that photon characteristics have been mainly examined by means of Klein-Gordon’s equation (Gottifried, 2003; Davidov, 1963; Messiah, 1970; Davydov, 1976), which represents eigen-problem of photon Hamiltonian square In this part of our paper we shall linearized photon Hamiltonian and examine some of photon characteristics witch follow from linearized Hamiltonian The analogy with Dirac’s approach to the problem of electrons will be used (Gottifried, 2003; Dirac, 1958) 505 Single Photon Eigen-Problem with Complex Internal Dynamics Firstly will be examined integrals of motion of free photon and will be shown that the photon integral of motion is not orbital momentum It will be shown that the integral of motion is total momentum being the sun of orbital one and spin momentum The evaluated Green’s function has given possibility for interpretation of photon reflection as a transformation of photon to anti-photon with energy change equal to double energy of photon and for spin change equal to Dirac’s constant (Dirac, 1958; Messiah, 1970) Since photon is relativistic quantum object the exact determining of its characteristics is impossible The discussion of obtained results and their comparison to the experimental data will be done at the last part 3.2 Linearized photon Hamiltonian We shall not deal with this eigen-problem in further of this paper Instead of this we shall look for integrals of motion, i.e those operators that commute with free-photon Hamiltonian (2.7) It is obvious that any function depending on momentum components represents an integral of motion, but this fact is not of physical interest It is of particular importance whether orbital momentum: ˆ ˆ ⎛ L = ⎜L ⎜0 ⎝ 0⎞; L = r × p ˆ ⎟ ˆ ˆ⎟ L⎠ (3.1) ˆ is photon integral of motion, since in non-relativistic quantum mechanics operator L is integral of motion of electron (Messiah, 1970; Davydov, 1976) The components of orbital momentum are given as follows: ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ Lx = ypz − zp y ; Ly = zp x − xpz ; Lz = xp y − yp x (3.2) If we use commutation relations for components of radius vector and the components of momentum: [xi,pj] = iħ δij, i,j ∈ (x,y,z) and look for commutators of (3.2) with Hamiltonian (2.7), we come to the following relations: ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ [Lˆ , H ] = ±i c(p βˆ − p χˆ ) ; [Lˆ , H ] = ±i c( p χˆ − p αˆ ) ; [Lˆ , H ] = ±i c(p αˆ − p βˆ ) , x z y y x z z y x (3.3) based on which it follows that orbital momentum is not a free photon integral of motion It should be pointed out that signs in (3.3) are obtained on the basis of obvious symmetry ˆ ˆ properties H (−r ) = H (r ) and L(−r ) = L(r ) , where r is radius-vector In order to find some rotation characteristics that commute with a free photon Hamiltonian, ˆ ˆ ˆ we shall first show that commutation relations for matrices α , β and χ , given in section 2.1 by expression (2.6), are: [αˆ , βˆ ]= 2iχˆ ; [βˆ, χˆ ]= 2iαˆ , ˆ ˆ ˆ [χ , α ] = 2iβ ; (3.4) while commutation relations for spin components (Dirac, 1958; Messiah, 1970): [Sˆ , Sˆ ] = i Sˆ x y z ; [Sˆ , Sˆ ] = i Sˆ z x y ; [Sˆ , Sˆ ] = i Sˆ , y z x (3.5) 506 Micro Electronic and Mechanical Systems are very similar to (3.4) Comparing (3.4) to (3.5) we can establish the correspondence ˆ ˆ ˆ between spin operator components and matrices α , β and χ : ˆ ˆ ˆ ˆ ˆ ˆ Sx = α ; S y = β ; Sz = χ 2 (3.6) ˆ ˆ ˆ Commutators of matrices α , β and χ with Hamiltonian are given by: ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ [αˆ , H ] = ∓2ic( p βˆ − p χˆ ) ; [βˆ , H ] = ∓2ic( p χˆ − p αˆ ) ; [χˆ , H ] = ∓2ic( p αˆ − p βˆ ) z y x z y x (3.7) ˆ We shall now look for a commutator of component J x of total momentum, with photon ˆ H (r ) Using upper signs in formulas (3.3) and (3.7) we obtain: Hamiltonian i.e with ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ [Jˆ , H (r )] = [(L + Sˆ ), H (r )] = ⎡(L + αˆ ), H (r )⎤ = [L , H (r )]+ [αˆ , H (r )] = ⎢ ⎥ ⎣ ⎦ x x x x ( ) x ( (3.8) ) ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ = i c pz β − p y χ + (−2ic) pz β − p y χ = For lower signs in formulas (3.3) and (3.7) 1, we have: ˆ ˆ [Jˆ , H (−r )] = [(L x ( x ] [ ] [ ] ⎡ ˆ ⎤ ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ + S x ), H (−r ) = ⎢( Lx + α ), H (−r )⎥ = Lx , H (−r ) + α , H (−r ) = 2 ⎣ ⎦ ) ( ) (3.9) ˆ ˆ ˆ ˆ ˆ ˆ ˆ ˆ = i c p z β − p y χ + (2ic) p z β − p y χ = It can be proved, in the same manner, that both y and z components of total momentum ˆ ˆ ˆ ˆ J = L + S commute with photon Hamiltonian (the expression (2.7) with sign +, i.e H (r ) ˆ will be called photon Hamiltonian) The expression (2.7) with sign –, i.e H (−r ) will be called anti-photon Hamiltonian In the same manner can be proved that y and z components ˆ ˆ ˆ of total momentum J = L − S commute with anti-photon Hamiltonian ˆ ˆ The final conclusion is the following: total momentum L + S is integral of motion for ˆ ˆ photon, while total momentum L − S is integral of motion for anti-photon Up to now we ˆ ˆ have the proof that total momentum L + S is free photon integral of motion, but we not know what magnitude of photon spin is If spin is S = 1/2, then the following relation is valid: (Sˆ x ˆ − iS y ) = (3.10) For spin S > 1/2 the exponent in (3.10) is higher than 2, i.e it must be 3,4, etc In (3.10) we ˆ ˆ shall go over to matrices α and β through relation (3.6) So we obtain: (Sˆ x ˆ − iS y ) = ˆ ˆ (α − iβ ) = ˆ ˆ ˆˆ ˆˆ [α − β + 2i (αβ + β α )] = ˆ this corresponds to negative photon energies, i.e corresponds to H (−r ) 507 Single Photon Eigen-Problem with Complex Internal Dynamics (in the last stage of the upper proof the relations (3.5) from section 2.1 were used) Consequently, we can conclude that free photon integral of motion represents a total momentum which is the sum of orbital momentum and spin momentum which corresponds to the case when S = 1/2 In the same way can be concluded that anti-photon integral of motion is the sum of orbital momentum and spin momentum which corresponds to spin S = –1/2 It should be noticed that negative spin is rather senseless concept so that ±S really means ±Sz , where Sz = ħ/2 In nonrelativistic quantum mechanics (Gottifried, 2003; Davidov, 1963) the conclusion that ˆ J is integral of motion would mean that energy and total momentum of the quantum object can be measured simultaneously and exactly Since photon is relativistic object (Berestetskii, et al., 1982) the maximal exactness of measuring of photon momentum is given by Δp Δt ~ ħ/c, and consequently energy and total momentum can be determined with an error of the ˆ order ΔE Δt ~ ħ The orbital momentum L , as it follows from (3.3), is not integral of motion, but for relativistic object this fact is not essential, since for relativistic objects absolutely exact determining of physical characteristics is in possible Considering the correspondence (3.6), photon Hamiltonian which is given by ˆˆ ˆ ˆˆ ˆˆ H = c αp x + β p y + χp z can be expressed by means of spin operators in the following form: ( ) ( ) ˆ ˆ ˆ ˆ ˆ ˆ ˆ 2c S p + S p + S p H= x x y y z z (3.11) The obtained form of photon Hamiltonian, which includes operators of translation moment ˆ ˆ P and spin S suggest that a free photon has wealthy internal dynamics that consists of mutual action of its translation and spin characteristics This “internal life” will be examined further in the paper 3.3 Unitary transformation of photon Hamiltonian Photon Hamiltonian (3.11) represents bilinear form in which photon momentum operators are multiplied by spin operators Since momentum characterizes translation photon motion, and spin characterizes rotation, it is obvious that the internal dynamic structure of a photon is determined by both its translation and rotation characteristics, and that their interaction – considering the form of Hamiltonian (3.11), leads to hybridization of excitations (Agranovich, 2009) Spin operators in (3.11) correspond to spin S = 1/2 and its can then is represented by Pauli’s operators in the following manner (Tyablikov, 1967): ˆ ˆ ˆ ˆ ˆ S x − iS y = P + ; S x + iS y = P ; − Sz = P+ P (3.12) Pauli’s operators fulfill commutation relations: [P , P ] = [1 − 2P P ]δ i + j + i j ij ; [P , P ] = [P i j i + ] , Pj+ = ; Pi = Pi +2 = ; (P P ) + e v ⎧0 ; =⎨ ⎩1 (3.13) After substitution of (3.12) in (3.11) (in this formula sign + is retained), we obtain the following form of Hamiltonian: 508 Micro Electronic and Mechanical Systems [ ] ˆ ˆ ˆ ˆ ˆ ˆ ˆ H = cp z + c ( p x − ip y ) P + ( p x + ip y ) P + − p z P + P (3.14) This conversion to Pauli operators has been made because the physical picture of processes is clearer through operator’s creation and annihilation of excitation Operators of moments are linear in operators of creation and annihilation of photon: P ∼ A + A+, so it can easily be concluded that mean value of photon Hamiltonian over states + n + ( A ) P is equal to zero This means that the method of theory of perturbation would n! be inappropriate for Hamiltonian (3.14) analysis This is why we would make unitary transformation of photon Hamiltonian with the goal to bring it into the form more suitable for calculation than the form (3.14), i.e we shall go to equivalent Hamiltonian given by: ˆ ˆ ˆ ˆ H eq = eW H e −W , (3.15) ˆ W = i kr + ρ (P − P + ) + i λ P + P , (3.16) where: and ρ and λ are real parameters Equivalent Hamiltonian is found using Weil’s identity (Tošić, 1978): ∞ ˆ ˆ [ [ [ [ ]] ] (1) n ˆ ˆ ˆ ˆ ˆ W , W , W , W , D n =0 n! ˆ eW D e −W = ∑ (3.17) n−times It has included the terms of the following type: P + P+, P – P+ and P+P Undetermined parameter λ has been determined so that the member proportional to P – P+ disappear from equivalent Hamiltonian The final result of the described procedure is as follows: ˆ ˆ ˆ H eq = E + H + H S , (3.18) ˆ where H is starting Hamiltonian, and E = c(k x sin ρ + k z cos ρ ) ; (3.19a) ˆ H S = − g ( P + P + ) + 2aP + P , (3.19b) where are: g = c k y + k x2 cos 2 ρ + k z2 sin 2 ρ − k x k z sin ρ ; a = c(k x sin ρ + k z cos ρ ) We shall further analyze free photon behavior using method of Green’s functions (Tyablikov, 1967; Tošić, 1978; Rickayzen, 1980; Mahan, 1990; Šetrajčić, et al., 2008) ˆ Hamiltonian E0 is irrelevant in Green function techniques Starting Hamiltonian H , as we have already concluded earlier, has zero mean value over states + n + ( A ) P This is why n! we shall exclude it from calculations The analysis of photon internal processes will be made ˆ with Hamiltonian H S 509 Single Photon Eigen-Problem with Complex Internal Dynamics 3.4 Green’s function of free photons ˆ Since Pauli operators figure in H S Hamiltonian without various configuration indices, the analysis of spin processes in a free photon will be made by means of anticommutator Pauli Green function: Γ (t ) = = Θ (t ) P (t ) P + ( ) + P + ( ) P (t ) , P (t ) P + ( ) (3.20) where Θ(t) is Heaviside’s step function (Tyablikov, 1967; Tošić, 1978; Rickayzen, 1980) Correlator of anticommutator Pauli’s Green’s function contains mean value of anticommutator of Pauli’s operator of the same configuration index, and according to (3.13) it is equal to one This fact simplifies evaluation of mean values by means of spectral intensity of Green function Differentiating Γ (t ) per time and using equation of motion for operator P, we come to the following equation: i The Green’s function of type: dΓ(t ) = i δ (t ) + 2a Γ(t ) + g Δ(t ) dt const P + Δ (t ) = (3.21) are equal to zero The function Δt is given by: P + (t ) P (t ) P + (0) (3.22) Using the same procedure, for defining function Δ(t) we obtain the following equation: i dΔ (t ) = g Γ(t ) − g F (t ) , dt (3.23) P + (t ) P + (0) , (3.24) where: F (t ) = with defining following equation: i dF (t ) = −2 g Δ (t ) − 2a F (t ) dt (3.25) In differential equations (3.21), (3.23) and (3.25), Furrier’s transformations time-frequency are then made: +∞ f (t ) = ∫ dt e − iωt f (ω ) ; f ≡ (Γ, Δ, F ); δ (t ) = −∞ 2π +∞ ∫ dt e − iωt , (3.26) −∞ so we obtain the system of algebraic equations: i ; 2π Δ (ω ) = g [Γ(ω ) − F (ω )]; ( E − 2a ) Γ(ω ) − g Δ (ω ) = E F (ω ) = −2 [g Δ (ω ) + a F (ω )] Solving this system of equations, we find that: (3.27) 510 Micro Electronic and Mechanical Systems Γ(ω ) = i E + 2aE − g , 2π ( E − E02 ) (3.28) where: E = a + g = ck (3.29) In order to determine spectral intensity of function Γ, it is necessary to break down the right side of the formula (3.20) into common fractions So, we obtain the following: Γ(ω ) = ⎛ g2 i ⎡ 2g ⎛ g a ⎞ a ⎞ ⎤ ⎟ +⎜ − + ⎢ ⎜2 E ⎟ ω − ω + ⎜ − E2 − E ⎟ ω + ω ⎥ , ⎜ ⎟ 2π ⎣ E0 ω ⎝ E0 ⎠ 0 0 ⎠ 0⎦ ⎝ (3.30) where: ω = E/ħ and ω0 = E0/ħ Since function Γ is anticommutator function, its spectral intensity is given by the formula (Tyablikov, 1967; Tošić, 1978; Rickayzen, 1980): Ι Γ (ω ) = Γ(ω + iδ ) + Γ(ω − iδ ) ω e k BT (3.31) ; δ → +0 , +1 and using Dirac’s formula: ω − ω k ± iδ ⎧ ⎫ = P.V ⎨ ⎬ ∓ iπ δ (ω − ω k ) , ⎩ω − ω k ⎭ (3.32) where P.V denotes principal value of integral, we find the explicit expression for spectral intensity: Ι Γ (ω ) = a ⎞ δ (ω − ω ) ⎛ g a ⎞ δ (ω + ω ) g δ (ω ) ⎛ g ⎟ ⎟ +⎜ − + +⎜ − − ω ⎜2 E ⎜2 E E0 k T E ⎟ k ωT E ⎟ k ωT 0 ⎝ ⎠ e +1 ⎝ ⎠ e +1 e +1 B B (3.33) B Now we can defined the expression for correlation function of a free photon as: +∞ ∫ P + (0) P(t ) ≡ dω e −iωt Ι Γ (ω ) = −∞ ⎛ g a ⎞ e iω t 2g ⎛ g a ⎞ e − iω t +⎜ − + ⎟ ω +⎜ − − ⎟ ω (3.34) ⎜ ⎟ E0 ⎜ E0 E0 ⎟ k T ⎝ ⎠ e + ⎝ E0 E0 ⎠ e k T + 0 B B Next, we can calculate expression for concentration of spin excitations of a free photon It is obtained from (3.34), if we take in it that t = 0, i.e P+P = ck a − k BT E0 (3.35) Combining formulae for a over formula (3.19b), and E0 from (3.29), and converting to sphere coordinate system, we find that: a = (sin ρ sin θ cos ϕ + cos ρ cosθ ) E0 In accordance with this and formula (3.35), we get the following expression for ordering parameter of spin subsystem in a free photon: 511 Single Photon Eigen-Problem with Complex Internal Dynamics σ = − P + P = (sin ρ sin θ cos ϕ + cos ρ cos θ ) ck k BT (3.36) The set of results of this section requires some explanations The most interesting results is that energy for spin translation from ħ/2 to –ħ/2 is ħck This can be explained on the basis of measuring process in which incident photon bean is reflected by measuring devices The momentum of incident phonon is ħk while the momentum reflected phonon is –ħk So we obtain the change of photon momentum Δp = ħk – (–ħk) = ħk, and consequently the energy change ΔE = ħck The energy –ħck corresponds to anti-photon, so that we can consider the described process as a transformation of photon to anti-photon In this process the spin change takes place, also (the Green’s function Γ(t ) = P (t ) P + (0) was calculated) Since photon and anti-photon spins have opposite signs the change the spin is ΔS = ħ/2 – (–ħ/2) = = ħ The value of ΔS is equal the value ħ and this is eigen-value of spin s = This is the reason for behaving of photon as particle with spin s = The polar and azimuthally dependences of ordering parameter comes from the fact that incident bean must not be always orthogonal to the plane of measuring device Conclusions The analysis of single photon behaving in coordinate systems of various geometries has shown the following: • In Cartesian coordinate system the components of single photon eigen-vector are progressive and regressive plane waves In other words, the photon behaving is characterized by coordinates and momentum, only • In cylindrical coordinate system the components of single photon eigen-vector of are progressive and regressive plane waves, but only along z axis In comparison to the results of analysis in Cartesian coordinates the fact that in x y planes photon oscillations are attenuated according to ρ–1/2 law represents a generalization This conclusion has been based on asymptotic behaving of Bessel functions • The most authentic result is obtained by the analysis in spherical coordinates Photon states not depend on angles, and they are damped according to r–1 law, where r is radius of the sphere It has also turned out that orbital momentum of a free photon is equal to zero (this is understandable considering the fact that it moves along a straight line) The important element determining the behavior of a free photon is spin One components of photon eigen-vector corresponds to spin Sz = 1/2 projection, while the other component corresponds to spin Sz = –1/2 projection This was concluded on the basis of the fact that its eigen-vector components are Bessel functions having indices +1/2 and –1/2 The last result shows that linearization of photon Hamiltonian gives more complete picture of single photon than Kline-Gordon’s approach Concluding the exposed analysis we shall try to connect the results obtained in series of experimental investigation of photon orbital momentum (Beth, 1936; Leach, et al., 2002; Allen, et al., 1992; Allen, 1966; He, et al., 1995; Friese, et al., 1996; Markoski, et al., 2008; van Enk & Nienhuis, 2007; Santamato, et al., 1988; O’Neil, et al., 2002; Volke-Sepulveda, et al., 2002) We shall not describe all quoted experiments Instead of it we shall describe the essential idea: the orbital momentum of photon was determines from the changes of 512 Micro Electronic and Mechanical Systems torque of rotating particles These changes where lied in some interval, so that the values of orbital momentum have had determined dispersion As it vas said at the end of first section, such result is expectable for relativistic objects, in this case for photons The azimuthally dependence of measured results is also predicted by the theory exposed in last Section Ending this analysis it should by noticed out that on the bases of given analysis the photon reflection can be considered as a transformation of photons to anti-photons Acknowledgements Investigations whose results are presented in this paper were partially supported by the Serbian Ministry of Sciences (Grant No 141044A) and by the Ministry of Sciences of Republic of Srpska References Agranovich, V.M (2009) Excitations in Organic Solids, University Press, ISBN 13 9780199234417, Oxford Allen, P.J.; 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Liu, R.B & Sham, L.J (2005) Theory of Control of the Spin-Photon Interface for Quantum Networks, Phys.Rev.Lett Vol.95, No.3, (Jul, 2005), pp.030504-030508 514 Micro Electronic and Mechanical Systems van Enk, J.S & Nienhuis, G (2007) Photons in Polychromatic Rotating Modes, Phys.Rev.A, Vol.76, No.5 (Nov.2007), pp.053825–1-11 Volke-Sepulveda, K.; Garcés-Chávez, V.; Chávez-Cerda, S.; Arlt, J & Dholakia, K (2002) Orbital angular momentum of a high-order Bessel light beam J.Opt.B: Quantum Semiclass.Opt Vol.4 (April 2002), pp.82-89 ... insignificantly higher error than the standard h.263 approach 488 stream size Micro Electronic and Mechanical Systems 1200000 h.263 h.263+PM 1000000 800000 600000 400000 200000 10 15 20 quantum Fig Dependence... determined in the standard way: E = ck = h 2π c c n = hν n ; ν = 2π L L (2.65) 504 Micro Electronic and Mechanical Systems This expression for energy is in full accordance with Plank’s hypothesis (Planck,... 506 Micro Electronic and Mechanical Systems are very similar to (3.4) Comparing (3.4) to (3.5) we can establish the correspondence ˆ ˆ ˆ between spin operator components and matrices α , β and