Noisy Quantum Metrology

As one of the pillar topics of the second quantum technological revolution,quantum metrology is the science of measurement that uses quantum entanglement or squeezing of microscopic many-body systems to achieve precision beyond that allowed by classical physics,and it is expected to provide new principle breakthroughs for future transformative atomic clocks,navigation,magnetic field measurements,and gravity measurements.However,quantum metrology is still at the proof-of-principle research stage,and its absolute accuracy is not yet comparable to current commercial schemes.One of the main obstacles to its experimental and applied progress is the noise-induced decoherence prevalent in the microscopic world,so understanding and controlling the decoherence and thus developing more stable means of regulating decoherence is a key scientific problem in this field.In this paper,to address this problem,we carry out the following noisy quantum metrology studies.First,we propose a quantum optical gyroscope scheme with excellent noise immunity characteristics.High-performance gyroscopes for rotation sensing are the main components of inertial navigation.Quantum metrology provides a new way to achieve the ultimate precision limit of gyroscopes.However,the stability of quantum gyroscopes is limited by the inevitable noise-induced decoherence in the microscopic world,which usually reduces the quantum resources of quantum gyroscopes and forces the quantum enhanced precsion back to the classical limit,and its quantum advantage disappears completely,which is called the no-go theorem of noisy quantum metrology and is one of the main bottlenecks to realize quantum gyroscopes.Therefore,how to break the constraint of the no-go theorem is the main challenge to achieve high precision quantum gyroscope.We propose a quantum optical gyroscope scheme that breaks the constraint of the no-go theorem.Its accuracy even surpasses the Heisenberg limit in the ideal decoherence-free case.In the decoherence case,we propose a quantum tuning mechanism that allows not only the encoding time as a resource but also the ideal super-Heisenberg limit to be recovered asymptotically: by tuning the operating frequency band of the optical probe so that it forms a bound state in a composite system with a noisy environment.Our results provide the first physical conditions for high-precision rotational sensing beyond the classical shot noise limit due to quantum entanglement in a realistic noisy environment,and provide an effective method to overcome the no-go theorem problem in noisy quantum metrology,which greatly expands the understanding of the decoherence effect in noisy quantum metrology.Second,we investigate the dissipative noise effect of Ramsey interferometer quantum metrology schemes based on multi-atomic spin squeezing.It has been shown that multi-atom spin squeezing is one of the important resources in quantum metrology and its use for Ramsey interferometry is the main principle to realize magnetometers,gyroscopes,atomic clocks,etc.in matter-wave systems beyond the classical shot noise limit.However,the noise induced decoherence poses a great challenge to the stability and integration of spin squeezing Ramsey interferometer,and how to recover the quantum gain of spin squeezing induced metrology accuracy under realistic noise conditions is the main difficulty in its implementation and application.We investigate the decoherence effect due to dissipative noise in the spin squeezing Ramsey interferometer and find that the quantum gain,stability and integration in the spin squeezing Ramsey interferometer metrology scheme are restored along with the formation of bound states in the energy spectrum of the composite system composed of probe atoms and the noisy environmen.The results reveal that the formation of bound states can be regulated by quantum reservoir engineering to counteract the dissipative noise in the spin squeezing Ramsey interferometer metrology scheme,which provides a theoretical basis for its application development.In conclusion,the results of this paper not only help to deepen our understanding of the noise effect of quantum metrology,but also help to understand the important role played by the noise present in the real physical environment in quantum metrology and provide a theoretical basis for the realization of quantum metrology.