Quantum-enhanced optical precision measurement assisted by low-frequency squeezed vacuum states

Stable low-frequency squeezed vacuum states at a wavelength of 1550 nm were generated.By controlling the squeezing angle of the squeezed vacuum states,two types of low-frequency quadrature-phase squeezed vacuum states and quadrature-amplitude squeezed vacuum states were obtained using one setup respectively.A quantum-enhanced fiber Mach–Zehnder interferometer(FMZI)was demonstrated for low-frequency phase measurement using the generated quadrature-phase squeezed vacuum states that were injected.When phase modulation was measured with the quantumenhanced FMZI,there were above 3 dB quantum improvements beyond the shot-noise limit(SNL)from 40 kHz to 200 kHz,and 2.3 dB quantum improvement beyond the SNL at 20 kHz was obtained.The generated quadrature-amplitude squeezed vacuum state was applied to perform low-frequency amplitude modulation measurement for sensitivity beyond the SNL based on optical fiber construction.There were about 2 dB quantum improvements beyond the SNL from 60 kHz to 200 kHz.The current scheme proves that quantum-enhanced fiber-based sensors are feasible and have potential applications in high-precision measurements based on fiber,particularly in the low-frequency range.

3D anchoring structured for LiFe_(0.5)Mn_(0.5)PO_(4)@cornstalk-C cathode materials

The organic carbon source coating LiFe_(x)Mn_(1-x)PO_(4)suffers from the problem of non-uniform carbon cladding.Too thick carbon cladding layer instead hinders the de-embedding of lithium ions.In this paper,we choose cornstalk as the carbon source,then LiFe_(0.5)Mn_(0.5)PO_(4)@cornstalk-C(LFMP@C-C)with 3D anchoring structure is prepared by the solvothermal method.The results show that the LFMP with cornstalk as the carbon source has better performance compared to the sucrose-coated LFMP material(LFMP@C).The discharge capacity of LFMP@C-C is 116 mAh/g for the first cycle at 1 C and the capacity retention rate is 94.0%after 500 cycles,and the discharge capacity of LFMP@C-C is more than 17.17%higher than that of LFMP@C.