1. A solution searching system by quantum dots comprising: an energy supply quantum dot having an energy level where exciter photons are generated in response to a supplied input light; a plurality of output display quantum dots each of which has a larger volume than the energy supply quantum dot and has a resonant level such that the output display quantum dots can emit an output light in response to an injection of the exciter photons, wherein the exciter photons are injected from an input quantum dot and with an energy level corresponding thereto; a light detection unit for detecting a light emission state of the output light for each of the plurality of output display quantum dots; a control light supply unit capable of supplying a control light to the output display quantum dots to control an intensity of the output light generated by the output display quantum dots in response to the injection of the exciter photons, the control light comprising controlling exciter photons; and a feedback control unit for controlling the control light to be supplied by the control light supply unit for each of the output display quantum dots based on the light emission state of the output light for each of the output display quantum dots detected by the light detection unit and previously-input search problem information, wherein the feedback control unit repeatedly performs supply control of the control light thereby to finally display a search solution for the previously-input search problem information based on the light emission state of the output light from each of the output display quantum dots detected by the light detection unit, wherein a propositional logical formula made of N variables as the previously-input search problem information is given and “true” or “false” of the variables is assigned to each of the output display quantum dots, a number of the output display quantum dots being 2N, wherein the feedback control unit determines whether the light emission state corresponds to “true” or “false” based on whether a light emission intensity of the output light emitted from each of the output display quantum dots exceeds a threshold, and wherein when there is provided, as the previously-input search problem information, a propositional logical formula in a conjunctive normal form in which AND of a plurality of terms is “true” and OR of two or three variables (literal) is given to each of the terms, and the output display quantum dots displaying “true” and “false” of one variable configuring the terms are in the light emission state, the feedback control unit controls the control light to be supplied by the control light supply unit in order to prevent a light emission of a quantum dot for which OR with a variable in the light emission state does not form “true” among the quantum dots displaying “true” and “false” of other variables configuring the terms.