Based on the scheme of damped harmonic oscillator quantization and thermo-field dynamics (TFD), the quantization of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling is propo...Based on the scheme of damped harmonic oscillator quantization and thermo-field dynamics (TFD), the quantization of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling is proposed. The quantum fluctuations of charge and current of each loop in a squeezed vacuum state are studied in the thermal excitation case. It is shown that the fluctuations not only depend on circuit inherent parameters, but also rely on excitation quantum number and squeezing parameter. Moreover, due to the finite environmental temperature and damped resistance, the fluctuations increase with the temperature rising, and decay with time.展开更多
The quantum fluctuations of a three-layer Heisenberg model with six sublattices are studied by the retarded Green's function method and the spin-wave theory. The effects of anisotropy on the quantum fluctuations at z...The quantum fluctuations of a three-layer Heisenberg model with six sublattices are studied by the retarded Green's function method and the spin-wave theory. The effects of anisotropy on the quantum fluctuations at zero temperature are discussed. The results show that the interlayer anisotropy plays an important role in balancing the quantum competitions.展开更多
Based on the Holstein model Hamiltonian of one-dimensional molecular crystals, by making use of the expansion approach of the correlated squeezed-coherent states of phonon instead of the two-phonon coherent state expa...Based on the Holstein model Hamiltonian of one-dimensional molecular crystals, by making use of the expansion approach of the correlated squeezed-coherent states of phonon instead of the two-phonon coherent state expansion scheme, the properties of the ground state and the anomalous quantum fluctuations are investigated in a strongly coupled electron-phonon system with special consideration of the electron-two-phonon interaction. The effective renormalization (ai) of the displacement of the squeezed phonons with the effect of the squeezed-coherent states of phonon and both the electron-displaced pbonon and the polaron-squeezed phonon correlations have been combined to obtain the anomalous quantum fluctuations for the corrections of the coherent state. Due to these non-adiabatic correlations, the effective displacement parameter ai is larger than the ordinary parameter ai (0) In comparison with the electron-one-phonon interaction (g) corrected as oig, we have found the electron-two-phonon interaction (gl) corrected as ai2gi is enhanced significantly. For this reason, the ground state energy (E(2)) contributed by the electron-two-phonon interaction is more negative than the single-phonon case (E01)) and the soliton solution is more stable. At the same time, the effects of the electron-two-phonon interaction greatly increase the polaron energy and the quantum fluctuations. Furthermore, in a deeper level, we have considered the effect of the polaron-squeezed phonon correlation (f-correlation). Since this correlation parameter f 〉 1, this effect will strengthen the electron-one and two-phonon interactions by fai9 and f2ai2g1, respectively. The final results show that the ground state energy and the polaron energy will appear more negative further and the quantum fluctuations will gain further improvement.展开更多
Using the theory of thermal field dynamics (TFD), a model polariton system is investigated and the squeezing properties of the polariton system at finite temperature is discussed. It is shown that when the photon fiel...Using the theory of thermal field dynamics (TFD), a model polariton system is investigated and the squeezing properties of the polariton system at finite temperature is discussed. It is shown that when the photon field is initially in a thermal vacuum state and the phonon initially in its lowest energy level state (the vacuum state), the phonon, photon and also the polariton system can exhibit nonclassical behaviour.展开更多
For time dependent inductive capacitive coupled circuits, the quantum fluctuations in the component circuits and the coupling part are computed. Generation of squeezing and the different effects of inductance and ca...For time dependent inductive capacitive coupled circuits, the quantum fluctuations in the component circuits and the coupling part are computed. Generation of squeezing and the different effects of inductance and capacitance couplings on the quantum fluctuations are rigorously given. Meanwhile, the thermal effects are included.展开更多
This paper stuides the magnetization and quantum fluctuations of an antiferro-antiferromagnetic (AF-AF) doublelayer at zero temperature. It is found that the exchanges and anisotropy constants affect the quantum flu...This paper stuides the magnetization and quantum fluctuations of an antiferro-antiferromagnetic (AF-AF) doublelayer at zero temperature. It is found that the exchanges and anisotropy constants affect the quantum fluctuations of spins. If the anisotropy exists, there will be no acoustic energy branch in the system. The anisotropy constant, antiferromagnetic intralayer and interlayer coupling have important roles in a balance of the quantum competition.展开更多
The ferroelectric transitions of several SrTiO3-based ferroelectrics are investigated experimentally and theoretically, with special attention to the critical scaling exponents associated with the phase transitions, i...The ferroelectric transitions of several SrTiO3-based ferroelectrics are investigated experimentally and theoretically, with special attention to the critical scaling exponents associated with the phase transitions, in order to understand the competition among quantum fluctuations (QFs), quenched disorder, and ferroelectric ordering. Two representative systems with sufficiently strong QFs and quenched disorders in competition with the ferroelectric ordering are investigated. We start from non-stoichiometric SrTiO3(STO) with the Sr/Ti ratio deviating slightly from one, which is believed to maintain strong QFs. Then, we address Ba/Ca co-doped Sr1-x(Ca0.6389Ba0.3611)xTiO3(SCBT) with the averaged Sr-site ionic radius identical to the Sr2+ ionic radius, which is believed to offer remarkable quenched disorder associated with the Sr-site ionic mismatch. The critical exponents associated with polarization P and dielectric susceptibility ε, respectively, as functions of temperature T close to the critical point Tc, are evaluated. It is revealed that both non-stoichiometric SrTiO3 and SCBT exhibit much bigger critical exponents than the Landau mean-field theory predictions. These critical exponents then decrease gradually with increasing doping level or deviation of Sr/Ti ratio from one. A transverse Ising model applicable to the Sr-site doped STO (e.g., Sr1-xCaxTiO3) at low level is used to explain the observed experimental data. It is suggested that the serious deviation of these critical exponents from the Landau theory predictions in these STO-based systems is ascribed to the significant QFs and quenched disorder by partially suppressing the long-range spatial correlation of electric dipoles around the transitions. The present work thus sheds light on our understanding of the critical behaviors of ferroelectric transitions in STO in the presence of quantum fluctuations and quenched disorder, whose effects have been demonstrated to be remarkable.展开更多
It is well known that the quantum fluctuation of entanglement(QFE) between Unruh–De Witt detector(modeled by a two-level atom) is always investigated in a relativistic setting. However, both of the Unruh radiation an...It is well known that the quantum fluctuation of entanglement(QFE) between Unruh–De Witt detector(modeled by a two-level atom) is always investigated in a relativistic setting. However, both of the Unruh radiation and quantum fluctuation effects play an important role in precise measurements of quantum entanglement. In this paper, we have quantitatively analyzed how the relativistic motion affects the QFE for two entangled Unruh–De Witt detectors, one of which is accelerated and interacting with the neighbor external scalar field. Our results show that the QFE, which initially increases by the Unruh thermal noise, will suddenly decay when the acceleration reaches to a considerably large value. Therefore, the relativistic effect will lead to non-negligible QFE effect. We also find that the initial QFE(without acceleration effect) reaches its minimum value at the maximally entangled state and the separable state. More importantly, our analysis demonstrates that although the QFE has a huge decay when the acceleration is greater than ~ 0.96, the ratio of △E/C is still very large, due to the simultaneous decay of concurrence to a very low value. Finally, enlightened by the well-known equivalence principle,we discuss the possibility of applying the above findings to the dynamics of QFE under the influence of gravitation field.展开更多
The influence of parameters such as the strength and frequency of a periodic driving force on the tunneling dynamics is investigated in a symmetric triple-well potential. It is shown that for some special values of th...The influence of parameters such as the strength and frequency of a periodic driving force on the tunneling dynamics is investigated in a symmetric triple-well potential. It is shown that for some special values of the parameters, tunneling could be enhanced considerably or suppressed completely. Quantum fluctuation during the tunneling is discussed as well and the numerical results are presented and analysed by virtue of Floquet formalism.展开更多
In this paper, with the full field operator ψ expressed in terms of a particle-number-conserving mean-field ansatz, we investigate the dynamical behaviour of Bose-Einstein condensates from microscopic physics. Includ...In this paper, with the full field operator ψ expressed in terms of a particle-number-conserving mean-field ansatz, we investigate the dynamical behaviour of Bose-Einstein condensates from microscopic physics. Including the first-order term correction from single-particle excitation and the remaining higher-order term correction from collective excitations simultaneously, we obtain the formulation for a closed local expression of quantum backreaction Q, and discuss the influence on static Bose-Einstein condensates. Even though the quantum backreaction is small, it still has some influence on its dynamics.展开更多
The quantum fluctuation of photon counting limits the field application of optical time domain reflection. A method of photon counts modulation optics time domain reflection with single photon detection at 1.55 μm is...The quantum fluctuation of photon counting limits the field application of optical time domain reflection. A method of photon counts modulation optics time domain reflection with single photon detection at 1.55 μm is presented. The influence of quantum fluctuation can be effectively controlled by demodulation technology since quantum fluctuation shows a uniform distribution in the frequency domain. Combined with the changing of the integration time of the lock-in amplifier, the signal to noise ratio is significantly enhanced. Accordingly the signal to noise improvement ratio reaches 31.7 dB compared with the direct photon counting measurement.展开更多
This paper reports that the mesoscopic inductance and capacitance coupling LC circuit is quantized by means of the canonical quantization method. Using the 'invariant eigen-operator' method, it deduces the energy-le...This paper reports that the mesoscopic inductance and capacitance coupling LC circuit is quantized by means of the canonical quantization method. Using the 'invariant eigen-operator' method, it deduces the energy-level transition rule when the system is disturbed by an external electromagnetic field. At the same time, the quantum fluctuations for the system at finite temperature are examined by virtue of the generalized Hellmann-Feynman theorem.展开更多
Quantum entangled states, especially those having particular properties, are key resources for quantum information and quantum computation. In this paper, we put forward a new scheme to produce 31 continuous-variable ...Quantum entangled states, especially those having particular properties, are key resources for quantum information and quantum computation. In this paper, we put forward a new scheme to produce 31 continuous-variable (CV) tripartite entanglement fields based on three optical frequency combs via cascade nonlinear processes in an optical parametric cavity, and investigate the spectral characteristics of three frequency combs. The center wavelengths of the three combs are designed as 852 nm, 780 nm (atomic transition lines), and 1550 nm (fiber communication wavelength). The positivity under partial transposition (PPT) criterion, which is sufficient and necessary, is used to evaluate the entanglement in each group of comb lines. This scheme is experimentally feasible and valuable for constructing quantum information networks in future.展开更多
The 1/f noise in multiwalled carbon nanotubes bundles has been investigated between the frequency range of 0.1 to 30 Hz. At room temperature the noise spectrum is standard 1/f, and its level is proportional to the squ...The 1/f noise in multiwalled carbon nanotubes bundles has been investigated between the frequency range of 0.1 to 30 Hz. At room temperature the noise spectrum is standard 1/f, and its level is proportional to the square of the bias voltage. With decreasing temperature the noise level also decreases. At 4.2 K the noise level follows a non-monotonic dependence against the bias voltage, showing a peak at a certain bias voltage, meanwhile its frequency dependence also deviates from the 1/f trend. This anomalous behaviour is discussed within the picture of environmental quantum fluctuation of charge transport in the samples.展开更多
For the density operator(mixed state) describing squeezed chaotic light(SCL) we search for its thermal vacuum state(a pure state) in the real-fictitious space. Using the method of integration within ordered prod...For the density operator(mixed state) describing squeezed chaotic light(SCL) we search for its thermal vacuum state(a pure state) in the real-fictitious space. Using the method of integration within ordered product(IWOP) of operators we find that it is a kind of one- and two-mode combinatorial squeezed state. Its application in evaluating the quantum fluctuation of photon number reveals: the stronger the squeezing is, the larger a fluctuation appears. The second-order degree of coherence of SCL is also deduced which shows that SCL is classic. The new thermal vacuum state also helps to derive the Wigner function of SCL.展开更多
We generalize the formalism proposed by Dalibard, Dupont-Roc, and Cohen-Tannoudji(the DDC formalism) in the fourth order for two atoms in interaction with scalar fields in vacuum to a thermal bath at finite temperatur...We generalize the formalism proposed by Dalibard, Dupont-Roc, and Cohen-Tannoudji(the DDC formalism) in the fourth order for two atoms in interaction with scalar fields in vacuum to a thermal bath at finite temperature T, and then calculate the interatomic interaction energy of two ground-state atoms separately in terms of the contributions of thermal fluctuations and the radiation reaction of the atoms and analyze in detail the thermal corrections to the van der Waals and Casimir–Polder interactions. We discover a particular region, i.e. 4(λ3β)(1/2) ■ L■λwith L, β and λ denoting the interatomic separation, the wavelength of thermal photons and the transition wavelength of the atoms respectively, where the thermal corrections remarkably render the van der Waals force, which is usually attractive, repulsive, leading to an interesting crossover phenomenon of the interatomic interaction from attractive to repulsive as the temperature increases. We also find that the thermal corrections cause significant changes to the Casimir–Polder force when the temperature is sufficiently high, resulting in an attractive force proportional to TL-3in the λ ■ β ■ L region, and a force that can be either attractive or repulsive and even vanishing in the β ■ λ ■ L region depending on the interatomic separation.展开更多
We explore the theoretical possibility that dark energy density is derived from massless scalar bosons in vacuum and present a physical model for dark energy. By assuming massless scalar bosons fall into the horizon b...We explore the theoretical possibility that dark energy density is derived from massless scalar bosons in vacuum and present a physical model for dark energy. By assuming massless scalar bosons fall into the horizon boundary of the cosmos with the expansion of the universe, we can deduce the uncertainty in the relative position of scalar bosons based on the quantum fluctuation of space-time and the assumption that scalar bosons satisfy P-symmetry under the parity transformation Pφ(r) =-φ(r), which can be used to estimate scalar bosons and dark energy density. Furthermore, we attempt to explain the origin of negative pressure from the increasing entropy density of the Boltzmann system and derive the equation for the state parameter, which is consistent with the specific equations of state for dark energy. Finally, we employ the SNIa Pantheon sample and Planck 2018 CMB angular power spectra to constrain the models and provide statistical results for the cosmology parameters.展开更多
In this paper,we investigate the photon correlations and the statistical properties of light produced by an optical cavity with an embedded quantum well interacting with squeezed light.We show that the squeezed source...In this paper,we investigate the photon correlations and the statistical properties of light produced by an optical cavity with an embedded quantum well interacting with squeezed light.We show that the squeezed source substantially improves the intensity of the emitted light and generates a narrowing and a duplication of the spectrum peaks.With a strong dependence on frequency detuning,the cavity produces considerably squeezed radiation,and perfect squeezing is predicted for weak light–matter interactions.Furthermore,the system under consideration presents a bunching effect of the transmitted radiation resulting from weak pumping of the coherent field.The results obtained may have potential applications in the fields of very accurate measurement and quantum computing.展开更多
Dimensionality is a central concept in developing the theory of low-dimensional physics.However,previous research on dimensional crossover in the context of a Bose-Einstein condensate(BEC)has focused on the single-com...Dimensionality is a central concept in developing the theory of low-dimensional physics.However,previous research on dimensional crossover in the context of a Bose-Einstein condensate(BEC)has focused on the single-component BEC.To our best knowledge,further consideration of the two-component internal degrees of freedom on the effects of dimensional crossover is still lacking.In this work,we are motivated to investigate the dimensional crossover in a three-dimensional(3D)Rabi-coupled two-component BEC.The spin degrees of freedom consist of the Rabi-like and inter-and intra-interaction coupling constants.The dimensional crossovers from 3D to 2D or 1D are controlled by the continuous increase of 1D or 2D lattice depth respectively.Then we analyze how the dimensionality of the model system combined with spin degrees of freedom can affect quantum fluctuations.Accordingly,the analytical expressions of the ground-state energy and quantum depletion of the system are obtained.Our results show that the dimensional crossover induces a characteristic 3D to quasi-2D or 1D crossover in the behavior of quantum fluctuations,with an emphasis on the separated effects of Rabi-like and inter-and intra-interaction coupling constants on the quantum fluctuations.Conditions for possible experimental realization of our scenario are also discussed.展开更多
We use the generalized uncertainty principle to compute the first correction to the Hawking temperature associated to Hawking effect.From this value we obtain a new evaporation time and entropy of any Schwarzschild bl...We use the generalized uncertainty principle to compute the first correction to the Hawking temperature associated to Hawking effect.From this value we obtain a new evaporation time and entropy of any Schwarzschild black hole analyzing their expressions and consequences.展开更多
基金Project supported by the Natural Science Foundation of Heze University of Shandong Province, China (Grant No XY05WL01), the University Experimental Technology Foundation of Shandong Province, China (Grant No S04W138), the Natural Science Foundation of Shandong Province, China (Grant No Y2004A09) and the National Natural Science Foundation of China (Grant No 10574060).
文摘Based on the scheme of damped harmonic oscillator quantization and thermo-field dynamics (TFD), the quantization of mesoscopic damped double resonance RLC circuit with mutual capacitance-inductance coupling is proposed. The quantum fluctuations of charge and current of each loop in a squeezed vacuum state are studied in the thermal excitation case. It is shown that the fluctuations not only depend on circuit inherent parameters, but also rely on excitation quantum number and squeezing parameter. Moreover, due to the finite environmental temperature and damped resistance, the fluctuations increase with the temperature rising, and decay with time.
基金Project supported by the Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University,China(Grant No.LZUMMM2010010)the Scientific Foundation of the Educational Department of Liaoning Province,China(Grant No.L2010390)+2 种基金the Natural Science Foundation of Liaoning Province of China(Grant No.20102171)the Scientific Technology Plan of Shenyang,China(Grant No.F10-205-1-33)the Excellent Talents Program of the University of Liaoning Province,China(Grant No.LR201031)
文摘The quantum fluctuations of a three-layer Heisenberg model with six sublattices are studied by the retarded Green's function method and the spin-wave theory. The effects of anisotropy on the quantum fluctuations at zero temperature are discussed. The results show that the interlayer anisotropy plays an important role in balancing the quantum competitions.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10574163)
文摘Based on the Holstein model Hamiltonian of one-dimensional molecular crystals, by making use of the expansion approach of the correlated squeezed-coherent states of phonon instead of the two-phonon coherent state expansion scheme, the properties of the ground state and the anomalous quantum fluctuations are investigated in a strongly coupled electron-phonon system with special consideration of the electron-two-phonon interaction. The effective renormalization (ai) of the displacement of the squeezed phonons with the effect of the squeezed-coherent states of phonon and both the electron-displaced pbonon and the polaron-squeezed phonon correlations have been combined to obtain the anomalous quantum fluctuations for the corrections of the coherent state. Due to these non-adiabatic correlations, the effective displacement parameter ai is larger than the ordinary parameter ai (0) In comparison with the electron-one-phonon interaction (g) corrected as oig, we have found the electron-two-phonon interaction (gl) corrected as ai2gi is enhanced significantly. For this reason, the ground state energy (E(2)) contributed by the electron-two-phonon interaction is more negative than the single-phonon case (E01)) and the soliton solution is more stable. At the same time, the effects of the electron-two-phonon interaction greatly increase the polaron energy and the quantum fluctuations. Furthermore, in a deeper level, we have considered the effect of the polaron-squeezed phonon correlation (f-correlation). Since this correlation parameter f 〉 1, this effect will strengthen the electron-one and two-phonon interactions by fai9 and f2ai2g1, respectively. The final results show that the ground state energy and the polaron energy will appear more negative further and the quantum fluctuations will gain further improvement.
文摘Using the theory of thermal field dynamics (TFD), a model polariton system is investigated and the squeezing properties of the polariton system at finite temperature is discussed. It is shown that when the photon field is initially in a thermal vacuum state and the phonon initially in its lowest energy level state (the vacuum state), the phonon, photon and also the polariton system can exhibit nonclassical behaviour.
文摘For time dependent inductive capacitive coupled circuits, the quantum fluctuations in the component circuits and the coupling part are computed. Generation of squeezing and the different effects of inductance and capacitance couplings on the quantum fluctuations are rigorously given. Meanwhile, the thermal effects are included.
基金supported by the Natural Science Foundation of the Educational Department of Liaoning Province,China (Grant Nos20060638 and 2008533)
文摘This paper stuides the magnetization and quantum fluctuations of an antiferro-antiferromagnetic (AF-AF) doublelayer at zero temperature. It is found that the exchanges and anisotropy constants affect the quantum fluctuations of spins. If the anisotropy exists, there will be no acoustic energy branch in the system. The anisotropy constant, antiferromagnetic intralayer and interlayer coupling have important roles in a balance of the quantum competition.
基金the National Basic Research Program of China(Grant Nos.2011CB922101 and 2009CB623303)the National Natural Science Foundation of China(Grant Nos.11234005 and 11074113)the Priority Academic Development Program of Jiangsu Higher Education Institutions,China
文摘The ferroelectric transitions of several SrTiO3-based ferroelectrics are investigated experimentally and theoretically, with special attention to the critical scaling exponents associated with the phase transitions, in order to understand the competition among quantum fluctuations (QFs), quenched disorder, and ferroelectric ordering. Two representative systems with sufficiently strong QFs and quenched disorders in competition with the ferroelectric ordering are investigated. We start from non-stoichiometric SrTiO3(STO) with the Sr/Ti ratio deviating slightly from one, which is believed to maintain strong QFs. Then, we address Ba/Ca co-doped Sr1-x(Ca0.6389Ba0.3611)xTiO3(SCBT) with the averaged Sr-site ionic radius identical to the Sr2+ ionic radius, which is believed to offer remarkable quenched disorder associated with the Sr-site ionic mismatch. The critical exponents associated with polarization P and dielectric susceptibility ε, respectively, as functions of temperature T close to the critical point Tc, are evaluated. It is revealed that both non-stoichiometric SrTiO3 and SCBT exhibit much bigger critical exponents than the Landau mean-field theory predictions. These critical exponents then decrease gradually with increasing doping level or deviation of Sr/Ti ratio from one. A transverse Ising model applicable to the Sr-site doped STO (e.g., Sr1-xCaxTiO3) at low level is used to explain the observed experimental data. It is suggested that the serious deviation of these critical exponents from the Landau theory predictions in these STO-based systems is ascribed to the significant QFs and quenched disorder by partially suppressing the long-range spatial correlation of electric dipoles around the transitions. The present work thus sheds light on our understanding of the critical behaviors of ferroelectric transitions in STO in the presence of quantum fluctuations and quenched disorder, whose effects have been demonstrated to be remarkable.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0402600)the National Natural Science Foundation of China(Grant Nos.11690023,11373014,and 11633001)the Beijing Talents Fund of Organization Department of Beijing Municipal Committee of the CPC,and the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB23000000).
文摘It is well known that the quantum fluctuation of entanglement(QFE) between Unruh–De Witt detector(modeled by a two-level atom) is always investigated in a relativistic setting. However, both of the Unruh radiation and quantum fluctuation effects play an important role in precise measurements of quantum entanglement. In this paper, we have quantitatively analyzed how the relativistic motion affects the QFE for two entangled Unruh–De Witt detectors, one of which is accelerated and interacting with the neighbor external scalar field. Our results show that the QFE, which initially increases by the Unruh thermal noise, will suddenly decay when the acceleration reaches to a considerably large value. Therefore, the relativistic effect will lead to non-negligible QFE effect. We also find that the initial QFE(without acceleration effect) reaches its minimum value at the maximally entangled state and the separable state. More importantly, our analysis demonstrates that although the QFE has a huge decay when the acceleration is greater than ~ 0.96, the ratio of △E/C is still very large, due to the simultaneous decay of concurrence to a very low value. Finally, enlightened by the well-known equivalence principle,we discuss the possibility of applying the above findings to the dynamics of QFE under the influence of gravitation field.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10974137 and 10775100)
文摘The influence of parameters such as the strength and frequency of a periodic driving force on the tunneling dynamics is investigated in a symmetric triple-well potential. It is shown that for some special values of the parameters, tunneling could be enhanced considerably or suppressed completely. Quantum fluctuation during the tunneling is discussed as well and the numerical results are presented and analysed by virtue of Floquet formalism.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 10704031 and 1087150)the Scientific Research Foundation for Returned Scholars, Ministry of Education of China+1 种基金the Foundation of Shandong Educational Committee, China (Grant No J08LI60)the Research Project of ‘SUST Spring Bud',China (Grant No 2008AZZ093)
文摘In this paper, with the full field operator ψ expressed in terms of a particle-number-conserving mean-field ansatz, we investigate the dynamical behaviour of Bose-Einstein condensates from microscopic physics. Including the first-order term correction from single-particle excitation and the remaining higher-order term correction from collective excitations simultaneously, we obtain the formulation for a closed local expression of quantum backreaction Q, and discuss the influence on static Bose-Einstein condensates. Even though the quantum backreaction is small, it still has some influence on its dynamics.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10674086 and 10934004)the National Natural Science Foundation for Excellent Research Team (Grant No. 60821004)+2 种基金the National Key Basic Research and Development Program of China (Grant No. 2010CB923103)the National High Technology Research and Development Program of China (Grant No. 2009AA01Z319)the Program for Top Science and Technology Innovation Teams and Top Young and Middleaged Innovative Talents of Shanxi Province
文摘The quantum fluctuation of photon counting limits the field application of optical time domain reflection. A method of photon counts modulation optics time domain reflection with single photon detection at 1.55 μm is presented. The influence of quantum fluctuation can be effectively controlled by demodulation technology since quantum fluctuation shows a uniform distribution in the frequency domain. Combined with the changing of the integration time of the lock-in amplifier, the signal to noise ratio is significantly enhanced. Accordingly the signal to noise improvement ratio reaches 31.7 dB compared with the direct photon counting measurement.
基金supported by the National Natural Science Foundation of China(Grant No 10574060)the Natural Science Foundation of Shandong Province of China(Grant No Q2007A01)
文摘This paper reports that the mesoscopic inductance and capacitance coupling LC circuit is quantized by means of the canonical quantization method. Using the 'invariant eigen-operator' method, it deduces the energy-level transition rule when the system is disturbed by an external electromagnetic field. At the same time, the quantum fluctuations for the system at finite temperature are examined by virtue of the generalized Hellmann-Feynman theorem.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11504218,11634008,11674203,11574187,61108003,and 61227902)the National Key Research and Development Program of China(Grant No.2016YFA0301404)
文摘Quantum entangled states, especially those having particular properties, are key resources for quantum information and quantum computation. In this paper, we put forward a new scheme to produce 31 continuous-variable (CV) tripartite entanglement fields based on three optical frequency combs via cascade nonlinear processes in an optical parametric cavity, and investigate the spectral characteristics of three frequency combs. The center wavelengths of the three combs are designed as 852 nm, 780 nm (atomic transition lines), and 1550 nm (fiber communication wavelength). The positivity under partial transposition (PPT) criterion, which is sufficient and necessary, is used to evaluate the entanglement in each group of comb lines. This scheme is experimentally feasible and valuable for constructing quantum information networks in future.
文摘The 1/f noise in multiwalled carbon nanotubes bundles has been investigated between the frequency range of 0.1 to 30 Hz. At room temperature the noise spectrum is standard 1/f, and its level is proportional to the square of the bias voltage. With decreasing temperature the noise level also decreases. At 4.2 K the noise level follows a non-monotonic dependence against the bias voltage, showing a peak at a certain bias voltage, meanwhile its frequency dependence also deviates from the 1/f trend. This anomalous behaviour is discussed within the picture of environmental quantum fluctuation of charge transport in the samples.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.1117511311447202and 11574295)
文摘For the density operator(mixed state) describing squeezed chaotic light(SCL) we search for its thermal vacuum state(a pure state) in the real-fictitious space. Using the method of integration within ordered product(IWOP) of operators we find that it is a kind of one- and two-mode combinatorial squeezed state. Its application in evaluating the quantum fluctuation of photon number reveals: the stronger the squeezing is, the larger a fluctuation appears. The second-order degree of coherence of SCL is also deduced which shows that SCL is classic. The new thermal vacuum state also helps to derive the Wigner function of SCL.
基金the NSFC under Grants No.11690034,No.12075084,No.11875172 and No.12047551,and No.12105061the K C Wong Magna Fund in Ningbo University
文摘We generalize the formalism proposed by Dalibard, Dupont-Roc, and Cohen-Tannoudji(the DDC formalism) in the fourth order for two atoms in interaction with scalar fields in vacuum to a thermal bath at finite temperature T, and then calculate the interatomic interaction energy of two ground-state atoms separately in terms of the contributions of thermal fluctuations and the radiation reaction of the atoms and analyze in detail the thermal corrections to the van der Waals and Casimir–Polder interactions. We discover a particular region, i.e. 4(λ3β)(1/2) ■ L■λwith L, β and λ denoting the interatomic separation, the wavelength of thermal photons and the transition wavelength of the atoms respectively, where the thermal corrections remarkably render the van der Waals force, which is usually attractive, repulsive, leading to an interesting crossover phenomenon of the interatomic interaction from attractive to repulsive as the temperature increases. We also find that the thermal corrections cause significant changes to the Casimir–Polder force when the temperature is sufficiently high, resulting in an attractive force proportional to TL-3in the λ ■ β ■ L region, and a force that can be either attractive or repulsive and even vanishing in the β ■ λ ■ L region depending on the interatomic separation.
基金Supported by Xiaofeng Yang’s Xinjiang Tianchi Bairen project and CAS Pioneer Hundred Talents Programpartly supported by the National Key R&D Program of China (2018YFA0404602)
文摘We explore the theoretical possibility that dark energy density is derived from massless scalar bosons in vacuum and present a physical model for dark energy. By assuming massless scalar bosons fall into the horizon boundary of the cosmos with the expansion of the universe, we can deduce the uncertainty in the relative position of scalar bosons based on the quantum fluctuation of space-time and the assumption that scalar bosons satisfy P-symmetry under the parity transformation Pφ(r) =-φ(r), which can be used to estimate scalar bosons and dark energy density. Furthermore, we attempt to explain the origin of negative pressure from the increasing entropy density of the Boltzmann system and derive the equation for the state parameter, which is consistent with the specific equations of state for dark energy. Finally, we employ the SNIa Pantheon sample and Planck 2018 CMB angular power spectra to constrain the models and provide statistical results for the cosmology parameters.
文摘In this paper,we investigate the photon correlations and the statistical properties of light produced by an optical cavity with an embedded quantum well interacting with squeezed light.We show that the squeezed source substantially improves the intensity of the emitted light and generates a narrowing and a duplication of the spectrum peaks.With a strong dependence on frequency detuning,the cavity produces considerably squeezed radiation,and perfect squeezing is predicted for weak light–matter interactions.Furthermore,the system under consideration presents a bunching effect of the transmitted radiation resulting from weak pumping of the coherent field.The results obtained may have potential applications in the fields of very accurate measurement and quantum computing.
基金supported by the Zhejiang Provincial Natural Science Foundation(Grant Nos.LZ21A040001 and LQ20A040004)the National Natural Science Foundation of China(Nos.12074344,and 12104407)the key projects of the Natural Science Foundation of China(Grant No.11835011).
文摘Dimensionality is a central concept in developing the theory of low-dimensional physics.However,previous research on dimensional crossover in the context of a Bose-Einstein condensate(BEC)has focused on the single-component BEC.To our best knowledge,further consideration of the two-component internal degrees of freedom on the effects of dimensional crossover is still lacking.In this work,we are motivated to investigate the dimensional crossover in a three-dimensional(3D)Rabi-coupled two-component BEC.The spin degrees of freedom consist of the Rabi-like and inter-and intra-interaction coupling constants.The dimensional crossovers from 3D to 2D or 1D are controlled by the continuous increase of 1D or 2D lattice depth respectively.Then we analyze how the dimensionality of the model system combined with spin degrees of freedom can affect quantum fluctuations.Accordingly,the analytical expressions of the ground-state energy and quantum depletion of the system are obtained.Our results show that the dimensional crossover induces a characteristic 3D to quasi-2D or 1D crossover in the behavior of quantum fluctuations,with an emphasis on the separated effects of Rabi-like and inter-and intra-interaction coupling constants on the quantum fluctuations.Conditions for possible experimental realization of our scenario are also discussed.
基金The author is partially supported by a MINECO/FEDER Grant Number 2017-84383-Pan AGAUR(Generalitat de Catalunya)Grant Number 2017SGR 1276.
文摘We use the generalized uncertainty principle to compute the first correction to the Hawking temperature associated to Hawking effect.From this value we obtain a new evaporation time and entropy of any Schwarzschild black hole analyzing their expressions and consequences.