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| We have investigated the noise spectrum of the system with a quantum dot (QD) coupled to two normal metal leads. A quantum electromagnetic field ( QEMF) is applied to the QD through its gate, and the dipole electric potential approximation is made in the system Hamiltonian. We have derived the tunneling current operator by employing the equation of motion approach, and the current operator is expressed by the Green's functions of QD and terminals. We have obtained the current correlation function through making ensemble average over a quantum state of QEMF, and the spectral density of noise is given by considering the expectation value over the lowest SU(1,1) coherent state. The noise spectral density is composed of thermal noise, quantum noise of QEMF, and the shot noise due to the nonequilibrium transport of charged particles. The quantum noise of the QEMF is transferred to the current noise, and the tunneling charged particles also play an important role since the formula of quantum noise is constructed by the transmission coefficient of electron. The shot noise and quantum noise belong to different types of noise, and their appearances display quite differently. The stair-like quantum noise behavior is obviously exhibited, and the positions of steps are located at the absorbed and emitted photon energies. |
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| Keywords:noise spectrum; quantum electromagnetic field; quantum do; current correlation |
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