Friedmann equation of cosmology is based on the field equations of general relativity. Its derivation is straight-forward once the Einstein’s field equations are given and the derivation is independent of quantum mec...Friedmann equation of cosmology is based on the field equations of general relativity. Its derivation is straight-forward once the Einstein’s field equations are given and the derivation is independent of quantum mechanics. In this paper, it is shown that the Friedmann equation pertinent to a homogeneous, isotropic and flat universe can also be obtained as a consequence of the energy balance in the expanding universe between the positive energy associated with vacuum and matter, and the negative gravitational energy. The results obtained here is a clear consequence of the fact that the surface area of the Hubble sphere is proportional to the total amount of information contained within it.展开更多
We calculate the time-energy distribution(TED)and ionization time distribution(ITD)of photoelectrons emitted by a doubleextreme-ultraviolet(XUV)pulse and a two-color XUV-IR pulse using the Wigner distribution-like fun...We calculate the time-energy distribution(TED)and ionization time distribution(ITD)of photoelectrons emitted by a doubleextreme-ultraviolet(XUV)pulse and a two-color XUV-IR pulse using the Wigner distribution-like function based on the strong field approximation.For a double-XUV pulse,besides two identical broad distributions generated by two XUV pulses,many interference fringes resulting from the interference between electrons generated,respectively,by two pulses appear in the TED.After adding an IR field,the TED intuitively exhibits the effect of the IR field on the electron dynamics.The ITDs during two XUV pulses are no longer the same and show the different changes for the different two-color fields,the origin of which is attributed to the change of the electric field induced by the IR field.Our analysis shows that the emission time of electrons ionized during two XUV pulses mainly depends on the electric field of the combined XUV pulse and IR pulse.展开更多
The measured data of vibrations induced by excavation of deep-buried cavern and open pit with method of bench blasting were analyzed by Fourier Transform and Wavelet Transform,and the characteristics of vibrations ind...The measured data of vibrations induced by excavation of deep-buried cavern and open pit with method of bench blasting were analyzed by Fourier Transform and Wavelet Transform,and the characteristics of vibrations induced under these two circumstances were studied.It is concluded that with the similar rock condition and drilling-blasting parameters,vibration induced by bench blasting in deep-buried cavern has a higher main frequency and more scattered energy distribution than that in open pit.The vibration induced by bench blasting in open pit is mainly originated from the blast load,while the vibration induced by bench blasting in deep-buried cavern is the superposition of vibrations induced by blast load and transient release of in-situ stress.The vibration induced by transient release of in-situ stress increases with the stress level.展开更多
The unified bound on the fundamental limit of quantum dynamics rate, as quietly recently obtainedby Levitin and Toffoli [Phys.Rev.Lett.103 (2009) 160502], is improved and refined.The improvement may bearbitrarily larg...The unified bound on the fundamental limit of quantum dynamics rate, as quietly recently obtainedby Levitin and Toffoli [Phys.Rev.Lett.103 (2009) 160502], is improved and refined.The improvement may bearbitrarily large in certain cases.In particular, this puts a limit on the operation rate of quantum gates allowed byquantum mechanics.展开更多
The action (the product of radiated energy and the time of emission) of the radiation fields generated by four types of radiators, namely, short electric dipole, small magnetic dipole, travelling wave antenna and bi-c...The action (the product of radiated energy and the time of emission) of the radiation fields generated by four types of radiators, namely, short electric dipole, small magnetic dipole, travelling wave antenna and bi-conical antenna is investigated with special reference to the charge associated with the current waveform which is responsible for the radiation. The results obtained can be summarized by the order of magnitude inequality where A is the action (product of the radiated energy and the time of emission), h is the Planck constant, q is the charge associated with the current that gave rise to the radiation and e is the electronic charge. The condition is obtained when the length of the antenna and its radius are pushed to its extreme natural limits. Based on the results obtained here and elsewhere, it is suggested that this inequality is valid in general for electromagnetic radiation fields as predicted by classical electrodynamics.展开更多
Quantum random number generators(QRNGs)can provide genuine randomness by exploiting the intrinsic probabilistic nature of quantum mechanics,which play important roles in many applications.However,the true randomness a...Quantum random number generators(QRNGs)can provide genuine randomness by exploiting the intrinsic probabilistic nature of quantum mechanics,which play important roles in many applications.However,the true randomness acquisition could be subjected to attacks from untrusted devices involved or their deviations from the theoretical modeling in real-life implementation.We propose and experimentally demonstrate a source-device-independent QRNG,which enables one to access true random bits with an untrusted source device.The random bits are generated by measuring the arrival time of either photon of the time–energy entangled photon pairs produced from spontaneous parametric downconversion,where the entanglement is testified through the observation of nonlocal dispersion cancellation.In experiment,we extract a generation rate of 4 Mbps by a modified entropic uncertainty relation,which can be improved to gigabits per second by using advanced single-photon detectors.Our approach provides a promising candidate for QRNGs with no characterization or error-prone source devices in practice.展开更多
Exploiting the fantastic features of quantum mechanics,a hyperentangled quantum network encoded in multiple degree of freedoms(DOF),e.g.,polarization and orbital angular momentum DOFs,can encode more qubits per transm...Exploiting the fantastic features of quantum mechanics,a hyperentangled quantum network encoded in multiple degree of freedoms(DOF),e.g.,polarization and orbital angular momentum DOFs,can encode more qubits per transmitted photon and offers a promising platform for many dramatic applications.Here,we demonstrate such a hyperentangled multiuser network with a fully connected network architecture by using dense wavelength division multiplexing and entanglement transfer technique.Three hyperentangled states in polarization and time-energy DOFs are multiplexed to three single mode fibers to form the fully connected network architecture.Then,three interferometric quantum gates are utilized for transferring quantum entanglement from time-energy to orbital angular momentum DOF.The experimental results reveal a high quality of the hyperentanglement of the constructed network with the entangled state fidelity of higher than 96%.Our approach can provide a novel way to construct a large-scale hyperentangled network that can support various kinds of quantum tasks like superdense coding and teleportation.展开更多
文摘Friedmann equation of cosmology is based on the field equations of general relativity. Its derivation is straight-forward once the Einstein’s field equations are given and the derivation is independent of quantum mechanics. In this paper, it is shown that the Friedmann equation pertinent to a homogeneous, isotropic and flat universe can also be obtained as a consequence of the energy balance in the expanding universe between the positive energy associated with vacuum and matter, and the negative gravitational energy. The results obtained here is a clear consequence of the fact that the surface area of the Hubble sphere is proportional to the total amount of information contained within it.
基金partially supported by the National Key Research and Development Program of China(Nos.2019YFA0307700and 2016YFA0401100)the National Natural Science Foundation of China(NSFC)(Nos.11774361,11775286,11804405,and 12047576)。
文摘We calculate the time-energy distribution(TED)and ionization time distribution(ITD)of photoelectrons emitted by a doubleextreme-ultraviolet(XUV)pulse and a two-color XUV-IR pulse using the Wigner distribution-like function based on the strong field approximation.For a double-XUV pulse,besides two identical broad distributions generated by two XUV pulses,many interference fringes resulting from the interference between electrons generated,respectively,by two pulses appear in the TED.After adding an IR field,the TED intuitively exhibits the effect of the IR field on the electron dynamics.The ITDs during two XUV pulses are no longer the same and show the different changes for the different two-color fields,the origin of which is attributed to the change of the electric field induced by the IR field.Our analysis shows that the emission time of electrons ionized during two XUV pulses mainly depends on the electric field of the combined XUV pulse and IR pulse.
基金Project(2010CB732003) supported by the National Basic Research Program of ChinaProjects(50725931,50779050 and 50909077) supported by the National Natural Science Foundation of China
文摘The measured data of vibrations induced by excavation of deep-buried cavern and open pit with method of bench blasting were analyzed by Fourier Transform and Wavelet Transform,and the characteristics of vibrations induced under these two circumstances were studied.It is concluded that with the similar rock condition and drilling-blasting parameters,vibration induced by bench blasting in deep-buried cavern has a higher main frequency and more scattered energy distribution than that in open pit.The vibration induced by bench blasting in open pit is mainly originated from the blast load,while the vibration induced by bench blasting in deep-buried cavern is the superposition of vibrations induced by blast load and transient release of in-situ stress.The vibration induced by transient release of in-situ stress increases with the stress level.
基金Supported by the National Natural Science Foundation of China under Grant No.10771208the Science Fund for Creative Research Groups under Grant No.10721101the Key Lab of Random Complex Structures and Data Science,CAS,under Grant No.2008DP173182
文摘The unified bound on the fundamental limit of quantum dynamics rate, as quietly recently obtainedby Levitin and Toffoli [Phys.Rev.Lett.103 (2009) 160502], is improved and refined.The improvement may bearbitrarily large in certain cases.In particular, this puts a limit on the operation rate of quantum gates allowed byquantum mechanics.
文摘The action (the product of radiated energy and the time of emission) of the radiation fields generated by four types of radiators, namely, short electric dipole, small magnetic dipole, travelling wave antenna and bi-conical antenna is investigated with special reference to the charge associated with the current waveform which is responsible for the radiation. The results obtained can be summarized by the order of magnitude inequality where A is the action (product of the radiated energy and the time of emission), h is the Planck constant, q is the charge associated with the current that gave rise to the radiation and e is the electronic charge. The condition is obtained when the length of the antenna and its radius are pushed to its extreme natural limits. Based on the results obtained here and elsewhere, it is suggested that this inequality is valid in general for electromagnetic radiation fields as predicted by classical electrodynamics.
基金supported by the National Key Research and Development Program of China (Grant No. 2019YFA0705000)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0301500)+1 种基金the Leading-edge Technology Program of Jiangsu Natural Science Foundation (Grant No. BK20192001)the National Natural Science Foundation of China (Grant Nos. 51890861 and 11974178).
文摘Quantum random number generators(QRNGs)can provide genuine randomness by exploiting the intrinsic probabilistic nature of quantum mechanics,which play important roles in many applications.However,the true randomness acquisition could be subjected to attacks from untrusted devices involved or their deviations from the theoretical modeling in real-life implementation.We propose and experimentally demonstrate a source-device-independent QRNG,which enables one to access true random bits with an untrusted source device.The random bits are generated by measuring the arrival time of either photon of the time–energy entangled photon pairs produced from spontaneous parametric downconversion,where the entanglement is testified through the observation of nonlocal dispersion cancellation.In experiment,we extract a generation rate of 4 Mbps by a modified entropic uncertainty relation,which can be improved to gigabits per second by using advanced single-photon detectors.Our approach provides a promising candidate for QRNGs with no characterization or error-prone source devices in practice.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.12192252 and 12074155)The Foundation for Shanghai Municipal Science and Technology Major Project(Grant No.2019SHZDZX01-ZX06)+1 种基金Jiangxi Provincial Natural Science Foundation(Grants No.20212ACB201004,Grant No.20202ACBL211003)funding provided by Shanghai Jiao Tong University.
文摘Exploiting the fantastic features of quantum mechanics,a hyperentangled quantum network encoded in multiple degree of freedoms(DOF),e.g.,polarization and orbital angular momentum DOFs,can encode more qubits per transmitted photon and offers a promising platform for many dramatic applications.Here,we demonstrate such a hyperentangled multiuser network with a fully connected network architecture by using dense wavelength division multiplexing and entanglement transfer technique.Three hyperentangled states in polarization and time-energy DOFs are multiplexed to three single mode fibers to form the fully connected network architecture.Then,three interferometric quantum gates are utilized for transferring quantum entanglement from time-energy to orbital angular momentum DOF.The experimental results reveal a high quality of the hyperentanglement of the constructed network with the entangled state fidelity of higher than 96%.Our approach can provide a novel way to construct a large-scale hyperentangled network that can support various kinds of quantum tasks like superdense coding and teleportation.
