In the field of quantum information, the acquisition of information for unknown quantum states is very important. When we only need to obtain specific elements of a state density matrix, the traditional quantum state tomography will become very complicated, because it requires a global quantum state reconstruction. Direct measurement of the quantum state allows us to obtain arbitrary specific matrix elements of the quantum state without state reconstruction, so direct measurement schemes have obtained extensive attention. Recently, some direct measurement schemes based on weak values have been proposed, but extra auxiliary states in these schemes are necessary and it will increase the complexity of the practical experiment. Meanwhile, the post-selection process in the scheme will reduce the utilization of resources. In order to avoid these disadvantages, a direct measurement scheme without auxiliary states is proposed in this paper. In this scheme, we achieve the direct measurement of quantum states by using quantum circuits, then we extend it to the measurement of general multi-particle states and complete the error analysis. Finally, when we take into account the dephasing of the quantum states, we modify the circuits and the modified circuits still work for the dephasing case.
ISSN: 1572-9494
Communications in Theoretical Physics reports important new theoretical developments in many different areas of physics and interdisciplinary research.
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Zhiyuan Wang et al 2023 Commun. Theor. Phys. 75 015101
Xingyu Qi et al 2024 Commun. Theor. Phys. 76 045602
Force spectrum measurements with constant loading rates are widely used in single-molecule manipulation experiments to study the mechanical stability and force response of biomolecules. Force-dependent transition rates can be obtained from the transition force distribution, but it is limited to the force range with non-zero force distribution. Although constant loading rate control can be realized with magnetic tweezers, the loading rate range is limited due to the slow movement of permanent magnets. Non-linear exponential and exponential squared force loading functions are more feasible in magnetic tweezers, while there is no theoretical result available for these two kinds of non-linear force loading functions. In this study, we solved the unfolding process of a protein following Bell's model under nonlinear exponential and exponential squared force loading functions, which offer a broader range of unfolding force distribution compared to the traditional constant loading rate experiments. Furthermore, we derived two force loading functions, which can produce uniform unfolding force distribution. This research contributes fundamental equations for the analysis of experimental data obtained through single-molecule manipulation under nonlinear force loading controls, paving the way for the use of nonlinear force control in magnetic tweezer experiments.
N Saber et al 2024 Commun. Theor. Phys. 76 045801
This research focuses on the electric behavior of a mixed ferrielectric sulflower-like nanostructure. The structure includes a core with spin atoms and a shell with spin atoms. The Blume–Capel model and the Monte Carlo technique (MCt) with the Metropolis algorithm are employed. Diagrams are established for absolute zero, investigating stable spin configurations correlated with various physical parameters. The MCt method explores phase transition behavior and electric hysteresis cycles under different physical parameters.
Cheng Chen et al 2024 Commun. Theor. Phys. 76 055004
In this paper, two different methods for calculating the conservation laws are used, these are the direct construction of conservation laws and the conservation theorem proposed by Ibragimov. Using these two methods, we obtain the conservation laws of the Gardner equation, Landau–Ginzburg–Higgs equation and Hirota–Satsuma equation, respectively.
Feifei Yang et al 2024 Commun. Theor. Phys. 76 035004
Nonlinear circuits can show multistability when a magnetic flux-dependent memristor (MFDM) or a charge-sensitive memristor (CSM) is incorporated into a one branch circuit, which helps estimate magnetic or electric field effects. In this paper, two different kinds of memristors are incorporated into two branch circuits composed of a capacitor and a nonlinear resistor, thus a memristive circuit with double memristive channels is designed. The circuit equations are presented, and the dynamics in this oscillator with two memristive terms are discussed. Then, the memristive oscillator is converted into a memristive map by applying linear transformation on the sampled time series for the memristive oscillator. The Hamilton energy function for the memristive oscillator is obtained by using the Helmholtz theorem, and it can be mapped from the field energy of the memristive circuit. An energy function for the dual memristive map is suggested by imposing suitable weights on the discrete energy function. The dynamical behaviors of the new memristive map are investigated, and an adaptive law is proposed to regulate the firing mode in the memristive map. This work will provide a theoretical basis and experimental guidance for oscillator-to-map transformation and discrete map energy calculation.
Yunqiu Ma et al 2024 Commun. Theor. Phys. 76 055603
The phase transition of water molecules in nanochannels under varying external electric fields is studied by molecular dynamics simulations. It is found that the phase transition of water molecules in nanochannels occurs by changing the frequency of the varying electric field. Water molecules maintain the ice phase when the frequency of the varying electric field is less than 16 THz or greater than 30 THz, and they completely melt when the frequency of the varying electric field is 24 THz. This phenomenon is attributed to the breaking of hydrogen bonds when the frequency of the varying electric field is close to their inherent resonant frequency. Moreover, the study demonstrates that the critical frequency varies with the confinement situation. The new mechanism of regulating the phase transition of water molecules in nanochannels revealed in this study provides a perspective for further understanding of the phase transition of water molecules in nanochannels, and has great application potential in preventing icing and deicing.
Wenxin Li et al 2023 Commun. Theor. Phys. 75 045503
In this paper, an active tunable terahertz bandwidth absorber based on single-layer graphene is proposed, which consists of a graphene layer, a photo crystal plate, and a gold substrate. When the Fermi energy (Ef) of graphene is 1.5 eV, the absorber shows high absorption in the range of 3.7 THz–8 THz, and the total absorption rate is 96.8%. By exploring the absorption mechanism of the absorber, the absorber shows excellent physical regulation. The absorber also shows good adjustability by changing the Ef of graphene. This means that the absorber exhibits excellent tunability by adjusting the physical parameters and Ef of the absorber. Meanwhile, the absorber is polarization independent and insensitive to the incident angle. The fine characteristics of the absorber mean that the absorber has superior application value in many fields such as biotechnology and space exploration.
Yu Sun et al 2021 Commun. Theor. Phys. 73 065603
Emergence refers to the existence or formation of collective behaviors in complex systems. Here, we develop a theoretical framework based on the eigen microstate theory to analyze the emerging phenomena and dynamic evolution of complex system. In this framework, the statistical ensemble composed of M microstates of a complex system with N agents is defined by the normalized N × M matrix A, whose columns represent microstates and order of row is consist with the time. The ensemble matrix A can be decomposed as , where , eigenvalue σI behaves as the probability amplitude of the eigen microstate UI so that and UI evolves following VI. In a disorder complex system, there is no dominant eigenvalue and eigen microstate. When a probability amplitude σI becomes finite in the thermodynamic limit, there is a condensation of the eigen microstate UI in analogy to the Bose–Einstein condensation of Bose gases. This indicates the emergence of UI and a phase transition in complex system. Our framework has been applied successfully to equilibrium three-dimensional Ising model, climate system and stock markets. We anticipate that our eigen microstate method can be used to study non-equilibrium complex systems with unknown order-parameters, such as phase transitions of collective motion and tipping points in climate systems and ecosystems.
Libin Fu 2024 Commun. Theor. Phys. 76 045101
By casting evolution to the Bloch sphere, the dynamics of 2 × 2 matrix non-Hermitian systems are investigated in detail. This investigation reveals that there are four kinds of dynamical modes for such systems. The different modes are classified by different kinds of fixed points, namely, the elliptic point, spiral point, critical node, and degenerate point. The Hermitian systems and the unbroken non-Hermitian cases belong to the category with elliptic points. The degenerate point just corresponds to the systems with exceptional point (EP). The topological properties of the fixed point are also discussed. It is interesting that the topological charge for the degenerate point is two, while the others are one.
Hao Wang 2024 Commun. Theor. Phys. 76 045102
We investigate nonclassical correlations via negativity, local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) for two-dimensional graphene lattices. The explicitly analytical expressions for negativity, LQU and LQFI are given. The close forms of LQU and LQFI confirm the inequality between the quantum Fisher information and skew information, where the LQFI is always greater than or equal to the LQU, and both show very similar behavior with different amplitudes. Moreover, the effects of the different system parameters on the quantified quantum correlation are analyzed. The LQFI reveals more nonclassical correlations than LQU in a two-dimensional graphene lattice system.
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Minghe Zhang and Zhenya Yan 2024 Commun. Theor. Phys. 76 065002
In this paper, we investigate the Cauchy problem of the Sasa–Satsuma (SS) equation with initial data belonging to the Schwartz space. The SS equation is one of the integrable higher-order extensions of the nonlinear Schrödinger equation and admits a 3 × 3 Lax representation. With the aid of the -nonlinear steepest descent method of the mixed -Riemann–Hilbert problem, we give the soliton resolution and long-time asymptotics for the Cauchy problem of the SS equation with the existence of second-order discrete spectra in the space-time solitonic regions.
Wenxin Li et al 2024 Commun. Theor. Phys. 76 065701
This study introduces an innovative dual-tunable absorption film with the capability to switch between ultra-wideband and narrowband absorption. By manipulating the temperature, the film can achieve multi-band absorption within the 30–45 THz range or ultra-wideband absorption spanning 30–130 THz, with an absorption rate exceeding 0.9. Furthermore, the structural parameters of the absorption film are optimized using the particle swarm optimization (PSO) algorithm to ensure the optimal absorption response. The absorption response of the film is primarily attributed to the coupling of guided-mode resonance and local surface plasmon resonance effects. The film's symmetric structure enables polarization incoherence and allows for tuning through various means such as doping/voltage, temperature and structural parameters. In the case of a multi-band absorption response, the film exhibits good sensitivity to refractive index changes in multiple absorption modes. Additionally, the absorption spectrum of the film remains effective even at large incidence angles, making it highly promising for applications in fields such as biosensing and infrared stealth.
S R Wu et al 2024 Commun. Theor. Phys. 76 065401
In this work, we investigate a static and spherically symmetric Bardeen–Kiselev black hole (BH) with the cosmological constant, which is a solution of the Einstein-non-linear Maxwell field equations. We compute the quasinormal frequencies for the Bardeen–Kiselev BH with the cosmological constant due to electromagnetic and gravitational perturbations. By varying the BH parameters, we discuss the behavior of both real and imaginary parts of the BH quasinormal frequencies and compare these frequencies with the Reissner–Nordström–de Sitter BH surrounded by quintessence (RN-dSQ). Interestingly, it is shown that the responses of the Bardeen–Kiselev BH with the cosmological constant and the RN-dSQ under electromagnetic perturbations are different when the charge parameter q, the state parameter w and the normalization factor c are varied; however, for the gravitational perturbations, the responses of the Bardeen–Kiselev BH with the cosmological constant and the RN-dSQ are different only when the charge parameter q is varied. Therefore, compared with the gravitational perturbations, the electromagnetic perturbations can be used to understand nonlinear and linear electromagnetic fields in curved spacetime separately. Another interesting observation is that, due to the presence of Kiselev quintessence, the electromagnetic perturbations around the Bardeen–Kiselev BH with the cosmological constant damps faster and oscillates slowly; for the gravitational perturbations, the quasinormal mode decays slowly and oscillates slowly. We also study the reflection and transmission coefficients along with the absorption cross section in the Bardeen–Kiselev BH with the cosmological constant; it is shown that the transmission coefficients will increase due to the presence of Kiselev quintessence.
Yuan Guo et al 2024 Commun. Theor. Phys. 76 065003
We present a flexible manipulation and control of solitons via Bose–Einstein condensates. In the presence of Rashba spin–orbit coupling and repulsive interactions within a harmonic potential, our investigation reveals the numerical local solutions within the system. By manipulating the strength of repulsive interactions and adjusting spin–orbit coupling while maintaining a zero-frequency rotation, diverse soliton structures emerge within the system. These include plane-wave solitons, two distinct types of stripe solitons, and odd petal solitons with both single and double layers. The stability of these solitons is intricately dependent on the varying strength of spin–orbit coupling. Specifically, stripe solitons can maintain a stable existence within regions characterized by enhanced spin–orbit coupling while petal solitons are unable to sustain a stable existence under similar conditions. When rotational frequency is introduced to the system, solitons undergo a transition from stripe solitons to a vortex array characterized by a sustained rotation. The rotational directions of clockwise and counterclockwise are non-equivalent owing to spin–orbit coupling. As a result, the properties of vortex solitons exhibit significant variation and are capable of maintaining a stable existence in the presence of repulsive interactions.
Xiaoyu Cheng and Qing Huang 2024 Commun. Theor. Phys. 76 065001
In this paper, the (1+1)-dimensional classical Boussinesq–Burgers (CBB) system is extended to a (4+1)-dimensional CBB system by using its conservation laws and the deformation algorithm. The Lax integrability, symmetry integrability and a large number of reduced systems of the new higher-dimensional system are given. Meanwhile, for illustration, an exact solution of a (1+1)-dimensional reduced system is constructed from the viewpoint of Lie symmetry analysis and the power series method.
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Shuang Wang and Miao Li 2023 Commun. Theor. Phys. 75 117401
We review the theoretical aspects of holographic dark energy (HDE) in this paper. Making use of the holographic principle (HP) and the dimensional analysis, we derive the core formula of the original HDE (OHDE) model, in which the future event horizon is chosen as the characteristic length scale. Then, we describe the basic properties and the corresponding theoretical studies of the OHDE model, as well as the effect of adding dark sector interaction in the OHDE model. Moreover, we introduce all four types of HDE models that originate from HP, including (1) HDE models with the other characteristic length scale; (2) HDE models with extended Hubble scale; (3) HDE models with dark sector interaction; (4) HDE models with modified black hole entropy. Finally, we introduce the well-known Hubble tension problem, as well as the attempts to alleviate this problem under the framework of HDE. From the perspective of theory, the core formula of HDE is obtained by combining the HP and the dimensional analysis, instead of adding a DE term into the Lagrangian. Therefore, HDE remarkably differs from any other theory of DE. From the perspective of observation, HDE can fit various astronomical data well and has the potential to alleviate the Hubble tension problem. These features make HDE a very competitive dark energy scenario.
Wei-jie Fu 2022 Commun. Theor. Phys. 74 097304
In this paper, we present an overview on recent progress in studies of QCD at finite temperature and densities within the functional renormalization group (fRG) approach. The fRG is a nonperturbative continuum field approach, in which quantum, thermal and density fluctuations are integrated successively with the evolution of the renormalization group (RG) scale. The fRG results for the QCD phase structure and the location of the critical end point (CEP), the QCD equation of state (EoS), the magnetic EoS, baryon number fluctuations confronted with recent experimental measurements, various critical exponents, spectral functions in the critical region, the dynamical critical exponent, etc, are presented. Recent estimates of the location of the CEP from first-principle QCD calculations within fRG and Dyson–Schwinger equations, which pass through lattice benchmark tests at small baryon chemical potentials, converge in a rather small region at baryon chemical potentials of about 600 MeV. A region of inhomogeneous instability indicated by a negative wave function renormalization is found with μB ≳ 420 MeV. It is found that the non-monotonic dependence of the kurtosis of the net-proton number distributions on the beam collision energy observed in experiments could arise from the increasingly sharp crossover in the regime of low collision energy.
Nicolas Michel et al 2022 Commun. Theor. Phys. 74 097303
Ab initio approaches are among the most advanced models to solve the nuclear many-body problem. In particular, the no-core–shell model and many-body perturbation theory have been recently extended to the Gamow shell model framework, where the harmonic oscillator basis is replaced by a basis bearing bound, resonance and scattering states, i.e. the Berggren basis. As continuum coupling is included at basis level and as configuration mixing takes care of inter-nucleon correlations, halo and resonance nuclei can be properly described with the Gamow shell model. The development of the no-core Gamow shell model and the introduction of the -box method in the Gamow shell model, as well as their first ab initio applications, will be reviewed in this paper. Peculiarities compared to models using harmonic oscillator bases will be shortly described. The current power and limitations of ab initio Gamow shell model will also be discussed, as well as its potential for future applications.
Xiang-Xiang Sun and Lu Guo 2022 Commun. Theor. Phys. 74 097302
In recent several years, the tensor force, one of the most important components of the nucleon–nucleon force, has been implemented in time-dependent density functional theories and it has been found to influence many aspects of low-energy heavy-ion reactions, such as dissipation dynamics, sub-barrier fusions, and low-lying vibration states of colliding partners. Especially, the effects of tensor force on fusion reactions have been investigated from the internuclear potential to fusion crosssections systematically. In this work, we present a mini review on the recent progress on this topic. Considering the recent progress of low-energy reaction theories, we will also mention more possible effects of the tensor force on reaction dynamics.
Chenyu Tang and Yanting Wang 2022 Commun. Theor. Phys. 74 097601
Ionic liquids (ILs), also known as room-temperature molten salts, are solely composed of ions with melting points usually below 100 °C. Because of their low volatility and vast amounts of species, ILs can serve as 'green solvents' and 'designer solvents' to meet the requirements of various applications by fine-tuning their molecular structures. A good understanding of the phase behaviors of ILs is certainly fundamentally important in terms of their wide applications. This review intends to summarize the major conclusions so far drawn on phase behaviors of ILs by computational, theoretical, and experimental studies, illustrating the intrinsic relationship between their dual ionic and organic nature and the crystalline phases, nanoscale segregation liquid phase, IL crystal phases, as well as phase behaviors of their mixture with small organic molecules.
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Yin
The emerging concept of multicaloric effects, introduced in 2010, entails the application of multiple interplay fields to a thermodynamic system. While multicaloric effects are main focus of experimental endeavors, theoretical considerations fall short of providing a thorough understanding. This paper introduces a comprehensive presentation on multicaloric effects, employing the method and theory of exterior derivative formations. It addresses every aspects of thermodynamic systems, showcasing its applicability to multicaloric materials (both single-phase and multi-phase materials), and its adaptability to different scenarios (either a single or multiple force fields). The formulation of Maxwell relationships, characterized by their generality and universality, enables a clear prediction in entropy and temperature, facilitating a distinct identification between independent and interdependent contributions from multicaloric effects.These insights hold significant importance in designing and developing specialized thermodynamic materials, optimizing functional performances and exploring innovative mechanisms.
Lin et al
A multi-relaxation-time discrete Boltzmann model (DBM) with split collision is proposed for both subsonic and supersonic compressible reacting flows, where chemical reactions take place among various components. The physical model is based on a unified set of discrete Boltzmann equations that describes the evolution of each chemical species with adjustable acceleration, specific heat ratio, and Prandtl number. On the righ-hand side of discrete Boltzmann equations, the collision, force, and reaction terms denote the change rates of distribution functions due to self- and cross-collisions, external forces, and chemical reactions, respectively. The source terms can be calculated in three ways, among which the matrix inversion method possesses the highest physical accuracy and computational efficiency. Through Chapman-Enskog analysis, it is proved that the DBM is consistent with the reactive Navier-Stokes equations, Fick's law and Stefan-Maxwell diffusion equation in the hydrodynamic limit. Compared with the one-step-relaxation model, the split collision model offers a detailed and precise description of hydrodynamic, thermodynamic, and chemical nonequilibrium effects. Finally, the model is validated by six benchmarks, including multicomponent diffusion, mixture in the force field, Kelvin-Helmholtz instability, flame at constant pressure, opposing chemical reaction, and steady detonation.
Liu et al
The Weyl double copy builds the relation between gauge theory and gravity theory, especially the correspondence between gauge solutions and gravity solutions. In this paper, we obtain the slowly rotating charge solutions from the Weyl double copy for the Kerr black hole with small Chern-Simons correction. Based on the Weyl double copy relation, for the Petrov type D solution in Chern-Simons modified gravity, we find the additional correction to the electromagnetic field strength tensor of the rotating charge. For the Petrov type I solution, we find that the additional electromagnetic field strength tensors have external sources, while the total sources vanish at the leading order.
Wang et al
It is well known that nonlocal coherence reflects nonclassical correlations better than quantum entan-
glement. Here, we analyze nonlocal coherence harvesting from the quantum vacuum to particle detectors
adiabatically interacting with a quantum scalar field in Minkowski spacetime. We find that the harvesting-
achievable separation range of nonlocal coherence is larger than that of quantum entanglement. As the
energy gap grows sufficiently large, the detectors harvest less quantum coherence, while the detectors could
extract more quantum entanglement from the vacuum state. Compared with the linear configuration and the
scalene configuration, we should choose the model of equilateral triangle configuration to harvest tripar-
tite coherence from the vacuum. Finally, we find a monogamous relationship, which means that tripartite
l1-norm of coherence is essentially bipartite types.
Zhang et al
Recently, a dual relation $T_0(n+1)=T_{HP}(n)$ between the minimum temperature ($T_0(n+1)$) black hole phase and the Hawking-Page transition ($T_{HP}(n)$) black hole phase in two successive dimensions was introduced in \cite{Wei:2020kra},
which was reminiscent of the AdS/CFT correspondence, as the Hawking-Page transition temperature could be treated as the temperature of the dual physical quantity on the boundary and the latter corresponds to the one in the bulk.
In this paper, we discuss the Hawking-Page transition and the dual relations in AdS black holes surrounded by dark energy in general dimensions.
Our findings reveal the occurrence of the Hawking-Page transition observed
between the thermal AdS radiation and thermodynamically stable large AdS black holes, 
both in the spacetime surrounded by phantom dark energy 
and the spacetime surrounded by quintessence dark energy.
We discuss the effects of the phantom dark energy and quintessence dark energy on the Hawking-Page transition temperature.
Especially for the dual relation,
it works well for the case of the AdS black holes surrounded by phantom dark energy.
While for the case of the AdS black holes surrounded by quintessence dark energy, 
the dual relation should be modified under an open assumption that the state parameter and the density parameter of the quintessence dark energy depend on the dimensions of the spacetime.