Enhance Light Field Compression Characteristics And Sub-SQL Measurement Based On Quantum Correlation Effect

Metrology is a comprehensive discipline that studies measurement and measurement sensitivity.With the rapid development of quantum mechanics and the continuous improvement of quantum resources,the combination of metrology and quantum mechanics at the micro level has gradually formed the frontier field of quantum precision measurement,which has received wide attention.Quantum precision measurement is to achieve high-resolution and high-sensitivity physical quantity measurement as the research goal.By using quantum mechanics theory to describe the physical system,it is expected to achieve higher measurement accuracy than classical measurement.Accurate measurement of physical quantities is the basis of scientific and technological progress,and quantum mechanics plays a central role in this challenge.On the one hand,due to the inevitable statistical uncertainty caused by quantum fluctuations,which brings basic limitations to high-precision measurement,quantum mechanics gives the measurement accuracy limit that classical metrology cannot break through,that is,the standard quantum limit;on the other hand,the use of some nonclassical properties of quantum mechanics,such as entanglement,coherence,and squeezing,can break through the standard quantum limit and realize quantum-enhanced measurement.In the development of quantum metrology,the cavity optomechanics plays a very important role recently,which has been widely investigated.The development of quantum technology has increased the accuracy of optical measurement to approaching the limit of quantum noise,which is usually works based on the removement of various classical technical noises through different effective methods.Moreover,for a statistical result in quantum mechanics,people usually use the standard deviation to measure how far a system deviates from its average.Quantum noise is also called quantum fluctuation or fluctuation variance.Vacuum fluctuation is a real existence predicted by quantum physics,which corresponds to the vacuum standard quantum limit(SQL)without any average particle number.It can exist in all kinds of ordinary classical light sources as a zero point.It is very important to accurately and reliably measure SQL.In the field of precision measurement and quantum optics research,the focus of everyone's attention is still how to break the standard quantum noise limit.We theoretically investigate the enhancement of the degree and bandwidth of squeezed states of light generated in cascaded optomechanical(OM)systems.With the obtained recursion relation of the generalized output quadratures,it is possible to realize cascaded OM systems operated simultaneously in a deamplification situation for the same quadrature with a frequency-dependent phase shift between cascaded systems.Due to the cumulative OM interaction,the degree of squeezing can be significantly improved and nearly independent of frequencies.Thus the squeezing frequency band is notably broadened.Moreover,the squeezing bandwidth can be further broadened through tuning the detunings between laser and cavity frequencies.Finally,the influence of optical losses on squeezing due to the inefficient transmission between cascaded systems is also taken into account,which degrades the squeezing via introducing uncorrelated vacuum noises.However,a better squeezed state is still achievable compared to that generated in single OM system.We also investigate the force measurement sensitivity in a squeezed dissipative optomechanics within the free-mass regime under the influence of shot noise(SN)from the photon number fluctuations,laser phase noise from the pump laser,thermal noise from the environment,and optical losses from outcoupling and detection inefficiencies.Generally,squeezed light could generate a reduced SN on the squeezed quadrature and an enlarged quantum backaction noise(QBA)due to the antisqueezed conjugate quadrature.With an appropriate choice of phase angle in homodyne detection,QBA is cancellable,leading to an exponentially improved measurement sensitivity for the SNdominated regime.By now,the effects of laser phase noise that is proportional to laser power emerge.The balance between squeezed SN and phase noise can lead to an subSQL sensitivity at an exponentially lower input power.However,the improvement by squeezing is limited by optical losses because high sensitivity is delicate and easily destroyed by optical losses.