Amplitude-squared compression of superposed states in vacuum and coherent states

The superposition state of vacuum state and coherent state amplitude squared compression Huang Sumei, Li Hongcai (College of Physics and Optoelectronics Information Science and Technology, Fujian Normal University, Fuzhou 350007, China) and the influence of superposition state amplitude squared compression of coherent states.

As we all know, the compression effect is a non-classical phenomenon unique to the quantum light field. It reflects the non-classical characteristics of the light field by a noise component that is lower than the coherent state. That is, the noise fluctuation of a certain orthogonal component in the compressed light is lower than the noise fluctuation of the corresponding component in the coherent state light field. Therefore, in practical applications, if the information is transmitted using this component, a higher signal-to-noise ratio than that of a coherent state light field can be obtained. Therefore, the compression effect of the optical field has a wide application prospect in the field of ultra-standard quantum limit high-precision optical measurement ultra-low noise optical communication and quantum communication. In 1987, M. Hillery proposed the concept of amplitude squared compression internationally for the first time on the basis of the concept of general compression. In this paper, the amplitude-squared compression of the superposition state of the vacuum state and the coherent state is studied. The effect of the p-coherence parameter (R, 0) of the superposition parameter on the amplitude squared compression of superposed states of the vacuum state and the coherent state is discussed.

1 The definition of amplitude squared compression is similar to the common single-mode electromagnetic field. Two orthogonal Hermite operators are defined to represent the real and imaginary parts of the square of the complex amplitude of the single mode light field. The operators X 1 and X2 satisfy the following commutation relations and uncertainty relationships: * The fund project: the Natural Science Foundation of Fujian Province (A0210014); the funded project of the Fujian Provincial Department of Education (JA02168) is called the light field if there is an inequality There is amplitude squared compression in the Xi direction. In order to characterize the degree of compression of the square of the light field, the degree of compression, Si, is introduced. Obviously, s, the amplitude of the superposition state of the vacuum state and the coherent state is the square of the superposition state of the vacuum state and the coherent state. T=R'exp(i9) (where R is a real number. The analytical expression of the degree of compression SkS2 obtained by (1)*(4) is visible, and the degree of compression S1S2 is a function of the superposition parameter; the p-coherence parameter (R,3). Now, S1S2 changes with 3,) and R, respectively, with -.

3 The influence of the superposition parameter p coherence parameter (R, 3) on the degree of compression. When R = 1, the degree of compression SkS2 changes with parameter 0. From available: The compression degree S1S2 changes periodically with parameter 3, and the period is 1 When S1Q is S2Q If the light field has amplitude squared compression in the X1 direction, the light field must not have amplitude squared compression in the 2 direction; If the light field has amplitude squared compression in the X2 direction, the light field must have no amplitude squared compression in the X1 direction. When 3 =, S1 takes the minimum value - the Q1163 light field has the deepest amplitude squared compression in the X1 direction. When 3=Q, S2 takes the minimum-Q light field and compresses the amplitude squared the deepest in the X2 direction. Therefore, the compression direction and depth can be changed by changing the compression degree S1S2 with the change of parameter 3.

For 1,3=Q, the degree of compression S1S2 varies with the parameter p. From: (1) When S1Q is S2Q, if the light field has amplitude squared compression in the X1 direction, then the light field must have no amplitude squared compression in the X2 direction; if the light field has amplitude squared compression in the X2 direction, Then the light field must have no amplitude squared compression in the X 1 direction.

(2) When the 7>> light field has no amplitude squared compression in the X1 direction. When p = tends to Q, the effect of P on the amplitude squared compression effect of the light field in the X 1 direction is not significant. (3) When p X2 direction is not (there is a Pan squared pressure% when >1*, the centroid is the amplitude squared compression in the 2 directions ft. When 1ci7d.net, S2 takes the minimum value of -01297 when P tends to +100 At this point, S2 tends to 0, which means that the effect of amplitude squared compression on the optical field in the X2 direction is not significant.(4) Comparing the compression of X1X2, it can be seen that the amplitude of the light field in the X2 direction is more squared than in the Xi direction. The amplitude squared compression effect is strong, so you can change the compression direction and depth by changing P.

However, S2 may be less than 0, ie, the light field does not have amplitude squared compression in the Xi direction, and there may be amplitude squared compression in the X2 direction. When R=167, S2 takes the minimum value of -02389 so the compression depth can be changed by changing R.

From the above analysis, we can see that for the superposed states of the vacuum state and the coherent state: (1) If the light field has amplitude squared compression in the X 1 direction, the light field must have no amplitude squared compression in the X2 direction; if the light field is in X If there is an amplitude squared compression in the 2 direction, the light field must have no amplitude squared compression in the Xi direction. (2) The direction and depth of amplitude squared compression can be controlled by changing the p-coherence parameter (R, 0) of the overlay parameter.

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