Quantum Enhancement of Phase Sensitivity for the Bright-Seeded SU (1,1) Interferometer with Direct Intensity Detection

Optical interferometers are widely used in many applications to accurately measure various physical quantities. The idea was first brought forward in the late ninetieth century by Mitchelson who constructed the first ever interferometer device. However, the recent technological advancement in the field of metrology has seen the development of more advanced optical interferometers with enhanced phase sensitivities. Consequently, alternative studies published in recent literature shows that the shot-noise limitations, a major drawback of the traditional interferometers, can be overcome by the influence of the quantum mechanics measurement systems.

Generally, the performance of a typical interferometer depends on the three main parts it comprises of, that is, the hardware structure, the injection state, and the detection scheme. To this note, different approaches have been developed for designing and constructing the parts, as a way of overcoming the shot-noise limit, therefore, resulting in different quantum interferometers. Among the available solutions, an SU (1,1) interferometer constructed by replacing the beam splitters with parametric amplifiers in the Mach-Zehnder interferometer exhibits enhanced sensitivity. Consequently, a recently constructed SU (1,1) interferometer has achieved the quantum enhancement of signal-to-noise ratio.

Unfortunately, it is difficult to measure simultaneously the noise and signal quantities of interferometers since they require different measuring instruments. This limits the devices applicability. In addition to the aforementioned physical quantities, phase sensitivity is an important factor in enhancing the performance of interferometer devices. However, little is known about the phase sensitivity used in bright seeded SU (1,1) interferometers.

In a recent research paper published in Physical Review Applied scientists at the East China Normal University: Dr. Shengshuai Liu, Dr. Yanbo Lou and Dr. Jun Xin and led by Professor Jietai Jing demonstrated the phase-sensitivity enhancement of such a bright seeded SU (1,1) interferometer compared with the shot-noise limit.

Briefly, the work entailed direct intensity detection method to measure the phase sensitivity of the bright-seeded SU (1,1) interferometer. Next, the obtained results were compared to those obtained by phase-sensitivity scaling using the shot-noise limit characterization of Mach-Zehnder interferometer.

The authors observed that by using the direct intensity detection, it was possible to measure the phase sensitivity of the bright-seeded SU (1,1) interferometer. Furthermore, it ensured real-time quantum improvements.

In summary, the experimental results clearly show the significant steps to demonstrate the enhancing performance of quantum interferometers by measuring the key physical quantities, that is, phase sensitivity, in real time. According to Professor Jietai Jing and his colleagues, the study does not only provide the desired information for further advancement of the quantum metrology but will also lead to numerous applications.