40 km fiber transmission of squeezed light measured with a real local oscillator

Abstract

We demonstrate the generation, 40 km fiber transmission, and homodyne detection of single-mode squeezed states of light at 1550 nm using real-time phase control of a locally generated local oscillator, often called a ''real local oscillator'' or ''local local oscillator''. The system was able to stably measure up to around 3.7 dB of noise suppression with a phase noise uncertainty of around 2.5○, using only standard telecom-compatible components and a field-programmable gate array (FPGA). The compactness, low degree of complexity and efficacy of the implemented scheme makes it a relevant candidate for long distance quantum communication in future photonic quantum networks.

Acousto-optic modulator-based bi-frequency interferometer for quantum technology

“…By slightly modifying the scheme [see Fig. 2(b)], the ABI can realize a frequency tuner scheme for quantum states, which can tune the frequency of a quantum optical state and fit that of the other quantum system [10,24] . In this scheme, a quantum state jψi ω is sent in at b port, and the â port is reserved for vacuum input.…”

“…Moreover, the visibility reduction problem can be in principle avoided if AOM 2 is directly used as the phase-shifting device of the phase-locking system. To complete this optimization, angle calculation and phase-unwrapping algorithms are necessary to be implemented in the FPGA [24] , and progress is underway.…”

Light squeezing enhancement by coupling nonlinear optical cavities

“…The squeezing property of light is an essential resource in various applications. Not only it is used to reduce the noise level in optical communication 16 , 17 and for the detection of extremely weak gravitational waves 18 , 19 , but also in quantum limited displacement sensing 20 , quantum cryptography 21 – 23 and quantum computing 24 – 26 . In quantum computing, the reduction of noise below the shot-noise level is used to avoid the loss of encoded information during quantum computation, which could lead to an accumulation of errors.…”

Effect of Wavefront Distortion on the Performance of Coherent Detection Systems: Theoretical Analysis and Experimental Research

“…Coherent detection is a key technology for improving the reception sensitivity of optical wireless coherent communication systems [1,2]. An optical wireless coherent communication system includes two detection methods: heterodyne and homodyne [3,4]. The distortion of the signal light wavefront caused by atmospheric turbulence and other factors destroys the spatial phase matching between the signal light and local oscillation light at the receiving end, leading to a decrease in the coherent detection efficiency at the receiving end [5].…”