This study addresses a challenge of parametrizing a resolution function of a neutron beam from the neutron time of flight facility n_TOF at CERN.A difficulty stems from a fact that a resolution function exhibits rathe...This study addresses a challenge of parametrizing a resolution function of a neutron beam from the neutron time of flight facility n_TOF at CERN.A difficulty stems from a fact that a resolution function exhibits rather strong variations in shape,over approximately ten orders of magnitude in neutron energy.To avoid a need for a manual identification of the appropri-ate analytical forms-hindering past attempts at its parametrization-we take advantage of the versatile machine learning techniques.Specifically,we parametrized it by training a multilayer feedforward neural network,relying on a key idea that such network acts as a universal approximator.The proof-of-concept is presented for a resolution function for the first experimental area of the n_TOF facility from the third phase of its operation.We propose an optimal network structure for a resolution function in question,which is also expected to be optimal or near-optimal for other experimental areas and for different phases of n_TOF operation.To reconstruct several resolution function forms in common use from a single para-metrized form,we provide a practical tool in the form of a specialized C++class encapsulating the computationally efficient procedures suited to the task.展开更多
We study the quantum phase transition from a superfluid to a Mott insulator of ultracold atoms in a threedimensional optical lattice with adjustable filling factors.Based on the density-adjustable Bose-Einstein conden...We study the quantum phase transition from a superfluid to a Mott insulator of ultracold atoms in a threedimensional optical lattice with adjustable filling factors.Based on the density-adjustable Bose-Einstein condensate we prepared,the excitation spectrum in the superfluid and the Mott insulator regime is measured with different ensemble-averaged filling factors.We show that for the superfluid phase,the center of the excitation spectrum is positively correlated with the ensemble-averaged filling factor,indicating a higher sound speed of the system.For the Mott insulator phase,the discrete feature of the excitation spectrum becomes less pronounced as the ensemble-averaged filling factor increases,implying that it is harder for the system to enter the Mott insulator regime with higher filling factors.The ability to manipulate the filling factor affords further potential in performing quantum simulation with cold atoms trapped in optical lattices.展开更多
We investigate the influence of a gravitational wave background on particles in circular motion. We are especially interested in waves leading to stationary orbits. This consideration is limited to circular orbits per...We investigate the influence of a gravitational wave background on particles in circular motion. We are especially interested in waves leading to stationary orbits. This consideration is limited to circular orbits perpendicular to the incidence direction. As a main result of our calculation, we obtain in addition to the well-known alteration of the radial distance a time dependent correction term for the phase modifying the circular motion of the particle. A background of gravitational waves creates some kind of uncertainty.展开更多
Establishing secure data communication necessitates secure key exchange over a public channel.Quantum key distribution(QKD),which leverages the principles of quantum physics,can achieve this with information-theoretic...Establishing secure data communication necessitates secure key exchange over a public channel.Quantum key distribution(QKD),which leverages the principles of quantum physics,can achieve this with information-theoretic security.The discrete modulated(DM)continuous variable(CV)QKD protocol,in particular,is a suitable candidate for large-scale deployment of quantum-safe communication due to its simplicity and compatibility with standard high-speed telecommunication technology.Here,we present the first experimental demonstration of a four-state DM CVQKD system,successfully generating composable finite-size keys,secure against collective attacks over a 20 km fiber channel with 2.3×10^(9) coherent quantum states,achieving a positive composable key rate of 11.04×10^(-3) bits/symbol.This accomplishment is enabled by using an advanced security proof,meticulously selecting its parameters,and the fast,stable operation of the system.Our results mark a significant step toward the large-scale deployment of practical,high-performance,cost-effective,and highly secure quantum key distribution networks using standard telecommunication components.展开更多
基金supported by the Croatian Science Foundation under the project number HRZZ-IP-2022-10-3878funding from the European Union’s Horizon Europe Research and Innovation programme under Grant Agreement No 101057511Funding Open access funding provided by CERN (European Organization for Nuclear Research).
文摘This study addresses a challenge of parametrizing a resolution function of a neutron beam from the neutron time of flight facility n_TOF at CERN.A difficulty stems from a fact that a resolution function exhibits rather strong variations in shape,over approximately ten orders of magnitude in neutron energy.To avoid a need for a manual identification of the appropri-ate analytical forms-hindering past attempts at its parametrization-we take advantage of the versatile machine learning techniques.Specifically,we parametrized it by training a multilayer feedforward neural network,relying on a key idea that such network acts as a universal approximator.The proof-of-concept is presented for a resolution function for the first experimental area of the n_TOF facility from the third phase of its operation.We propose an optimal network structure for a resolution function in question,which is also expected to be optimal or near-optimal for other experimental areas and for different phases of n_TOF operation.To reconstruct several resolution function forms in common use from a single para-metrized form,we provide a practical tool in the form of a specialized C++class encapsulating the computationally efficient procedures suited to the task.
基金Supported by the National Natural Science Foundation of China(Grant Nos.61703025,91736208,1150432&and 11920101004)the National Program on Key Basic Research Project of China(Grant Nos.2016YFA0301501 and 2017YFA0304204).
文摘We study the quantum phase transition from a superfluid to a Mott insulator of ultracold atoms in a threedimensional optical lattice with adjustable filling factors.Based on the density-adjustable Bose-Einstein condensate we prepared,the excitation spectrum in the superfluid and the Mott insulator regime is measured with different ensemble-averaged filling factors.We show that for the superfluid phase,the center of the excitation spectrum is positively correlated with the ensemble-averaged filling factor,indicating a higher sound speed of the system.For the Mott insulator phase,the discrete feature of the excitation spectrum becomes less pronounced as the ensemble-averaged filling factor increases,implying that it is harder for the system to enter the Mott insulator regime with higher filling factors.The ability to manipulate the filling factor affords further potential in performing quantum simulation with cold atoms trapped in optical lattices.
文摘We investigate the influence of a gravitational wave background on particles in circular motion. We are especially interested in waves leading to stationary orbits. This consideration is limited to circular orbits perpendicular to the incidence direction. As a main result of our calculation, we obtain in addition to the well-known alteration of the radial distance a time dependent correction term for the phase modifying the circular motion of the particle. A background of gravitational waves creates some kind of uncertainty.
基金funded within the QuantERA II Programme(project CVSTAR)that has received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No 101017733Innovation Fund Denmark(IFD)under Grant Agreement No 731473+5 种基金the Austrian Research Promotion Agency(FFG),project number FO999891361from the European Union’s Digital Europe programme under Grant Agreement No 101091659(QCI.DK)from the European Union’s Horizon Europe research and innovation programme under the project“Quantum Security Networks Partnership”(QSNP,grant agreement no.101114043)A.A.E.H.,U.L.A.and T.G.acknowledge support from Innovation Fund Denmark(CryptQ,0175-00018A)the Danish National Research Foundation,Center for Macroscopic Quantum States(bigQ,DNRF142)A.A.E.H.,R.Z.and T.G.acknowledge funding from the Carlsberg Foundation,project CF21-0466.
文摘Establishing secure data communication necessitates secure key exchange over a public channel.Quantum key distribution(QKD),which leverages the principles of quantum physics,can achieve this with information-theoretic security.The discrete modulated(DM)continuous variable(CV)QKD protocol,in particular,is a suitable candidate for large-scale deployment of quantum-safe communication due to its simplicity and compatibility with standard high-speed telecommunication technology.Here,we present the first experimental demonstration of a four-state DM CVQKD system,successfully generating composable finite-size keys,secure against collective attacks over a 20 km fiber channel with 2.3×10^(9) coherent quantum states,achieving a positive composable key rate of 11.04×10^(-3) bits/symbol.This accomplishment is enabled by using an advanced security proof,meticulously selecting its parameters,and the fast,stable operation of the system.Our results mark a significant step toward the large-scale deployment of practical,high-performance,cost-effective,and highly secure quantum key distribution networks using standard telecommunication components.
