| （英） |
Homodyne detection is widely used as a means of measuring the quadrature-phase amplitude of light, and in order to speed up continuous-variable quantum information processing, we need a broadband balanced detector which operates at the quantum noise limit. In this study, we evaluate the performance of a broadband low-noise balanced detector by measuring the quadrature-phase amplitudes of the vacuum state. The noise clearance (the increase of the quantum noise relative to the detector noise power) is 12.5dB at 7GHz, and 10dB at 8GHz, showing that a broadband low-noise homodyne detection is achieved. In addition, the linearity (the linear response of the detector noise power relative to the optical power of the local oscillator light) over broad frequency range is confirmed, allowing us to use the detector to perform a higher rate continuous-variable quantum key distribution (CV-QKD) than previous experiments. |