Federated Reinforcement Learning with Adaptive Training Times for Edge Caching

To relieve the backhaul link stress and reduce the content acquisition delay,mobile edge caching has become one of the promising approaches.In this paper,a novel federated reinforcement learning(FRL)method with adaptive training times is proposed for edge caching.Through a new federated learning process with the asynchronous model training process and synchronous global aggregation process,the proposed FRL-based edge caching algorithm mitigates the performance degradation brought by the non-identically and independently distributed(noni.i.d.)characteristics of content popularity among edge nodes.The theoretical bound of the loss function difference is analyzed in the paper,based on which the training times adaption mechanism is proposed to deal with the tradeoff between local training and global aggregation for each edge node in the federation.Numerical simulations have verified that the proposed FRL-based edge caching method outperforms other baseline methods in terms of the caching benefit,the cache hit ratio and the convergence speed.

Quantum multiparameter estimation with multimode photon catalysis entangled squeezed state

We propose a method to generate the multi-mode entangled catalysis squeezed vacuum states(MECSVS)by embedding the cross-Kerr nonlinear medium into the Mach–Zehnder interferometer.This method realizes the exchange of quantum states between different modes based on Fredkin gate.In addition,we study the MECSVS as the probe state of multi-arm optical interferometer to realize multi-phase simultaneous estimation.The results show that the quantum Cramer–Rao bound(QCRB)of phase estimation can be improved by increasing the number of catalytic photons or decreasing the transmissivity of the optical beam splitter using for photon catalysis.In addition,we also show that even if there is photon loss,the QCRB of our photon catalysis scheme is lower than that of the ideal entangled squeezed vacuum states(ESVS),which shows that by performing the photon catalytic operation is more robust against photon loss than that without the catalytic operation.The results here can find applications in quantum metrology for multiparatmeter estimation.

Quantum-enhanced stochastic phase estimation with the Su(1,1)interferometer

Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters.Similar to the estimation of a constant phase,there is a standard quantum limit for stochastic phase estimation,which can be obtained with the Mach-Zehnder interferometer and coherent input state.Recently,it has been shown that the stochastic standard quantum limit can be surpassed with nonclassical resources such as squcezed light.However,practical methods to achieve quantum enhancement in the stochastic phase estimation remain largely unexplored.Here we propose a method utilizing the SU(1,1)interferometer and coherent input states to cstimate a stochastic optical phase.As an example,we investigate the Ornstcin-Uhlenback stochastic phase.We analyze the performance of this method for three key estimation problems:prediction,tracking,and smoothing.The results show significant reduction of the mean square error compared with the Mach-Zehnder interferometer under the same photon number flux inside the interferometers.In particular,we show that the method with the SU(1,1)interferometer can achieve fundamental quantum scaling,achieve stochastic Heisenberg scalinga and surpass the precision of the canonical measurement.

Representation of the coherent state for a beam splitter operator and its applications

A beam splitter operator is a very important linear device in the field of quantum optics and quantum information.It can not only be used to prepare complete representations of quantum mechanics,entangled state representation,but it can also be used to simulate the dissipative environment of quantum systems.In this paper,by combining the transform relation of the beam splitter operator and the technique of integration within the product of the operator,we present the coherent state representation of the operator and the corresponding normal ordering form.Based on this,we consider the applications of the coherent state representation of the beam splitter operator,such as deriving some operator identities and entangled state representation preparation with continuous-discrete variables.Furthermore,we extend our investigation to two single and two-mode cascaded beam splitter operators,giving the corresponding coherent state representation and its normal ordering form.In addition,the application of a beam splitter to prepare entangled states in quantum teleportation is further investigated,and the fidelity is discussed.The above results provide good theoretical value in the fields of quantum optics and quantum information.