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
Chaudry Masood Khalique and Mduduzi Yolane Thabo Lephoko 2024 Commun. Theor. Phys. 76 045006
This paper is devoted to the investigation of the Landau–Ginzburg–Higgs equation (LGHe), which serves as a mathematical model to understand phenomena such as superconductivity and cyclotron waves. The LGHe finds applications in various scientific fields, including fluid dynamics, plasma physics, biological systems, and electricity-electronics. The study adopts Lie symmetry analysis as the primary framework for exploration. This analysis involves the identification of Lie point symmetries that are admitted by the differential equation. By leveraging these Lie point symmetries, symmetry reductions are performed, leading to the discovery of group invariant solutions. To obtain explicit solutions, several mathematical methods are applied, including Kudryashov's method, the extended Jacobi elliptic function expansion method, the power series method, and the simplest equation method. These methods yield solutions characterized by exponential, hyperbolic, and elliptic functions. The obtained solutions are visually represented through 3D, 2D, and density plots, which effectively illustrate the nature of the solutions. These plots depict various patterns, such as kink-shaped, singular kink-shaped, bell-shaped, and periodic solutions. Finally, the paper employs the multiplier method and the conservation theorem introduced by Ibragimov to derive conserved vectors. These conserved vectors play a crucial role in the study of physical quantities, such as the conservation of energy and momentum, and contribute to the understanding of the underlying physics of the system.
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.
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.
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.
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.
Wentao Qi et al 2024 Commun. Theor. Phys. 76 035103
Fundamental matrix operations and solving linear systems of equations are ubiquitous in scientific investigations. Using the 'sender-receiver' model, we propose quantum algorithms for matrix operations such as matrix-vector product, matrix-matrix product, the sum of two matrices, and the calculation of determinant and inverse matrix. We encode the matrix entries into the probability amplitudes of the pure initial states of senders. After applying proper unitary transformation to the complete quantum system, the desired result can be found in certain blocks of the receiver's density matrix. These quantum protocols can be used as subroutines in other quantum schemes. Furthermore, we present an alternative quantum algorithm for solving linear systems of equations.
Ruo-Qing Ding et al 2024 Commun. Theor. Phys. 76 045301
We study the dissociation of ψ(3770), ψ(4040), ψ(4160), and ψ(4415) mesons in collision with nucleons, which takes place in high-energy proton-nucleus collisions. The quark interchange between a nucleon and a meson leads to the dissociation of the meson. We consider the reactions: , , , , , , , , , and , where R stands for ψ(3770), ψ(4040), ψ(4160), or ψ(4415). A reaction of a neutron and a meson corresponds to a reaction of a proton and the meson by replacing the up quark with the down quark and vice versa. Transition-amplitude formulas are derived from the S-matrix element. Unpolarized cross sections are calculated with the transition amplitudes for scattering in the prior form and in the post form. The cross sections relate to nodes in the radial wave functions of ψ(3770), ψ(4040), ψ(4160), and ψ(4415) mesons.
Haiyang Hou et al 2024 Commun. Theor. Phys. 76 045005
We construct an integrable 1D extended Hubbard model within the framework of the quantum inverse scattering method. With the help of the nested algebraic Bethe ansatz method, the eigenvalue Hamiltonian problem is solved by a set of Bethe ansatz equations, whose solutions are supposed to give the correct energy spectrum.
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.
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Haifa A Alyousef et al 2024 Commun. Theor. Phys. 76 055005
This study reports the analytical solution for a generalized rotational pendulum system with gallows and periodic excited forces. The multiple scales method (MSM) is applied to solve the proposed problem. Several types of rotational pendulum oscillators are studied and talked about in detail. These include the forced damped rotating pendulum oscillator with gallows, the damped standard simple pendulum oscillator, and the damped rotating pendulum oscillator without gallows. The MSM first-order approximations for all the cases mentioned are derived in detail. The obtained results are illustrated with concrete numerical examples. The first-order MSM approximations are compared to the fourth-order Runge–Kutta (RK4) numerical approximations. Additionally, the maximum error is estimated for the first-order approximations obtained through the MSM, compared to the numerical approximations obtained by the RK4 method. Furthermore, we conducted a comparative analysis of the outcomes obtained by the used method (MSM) and He-MSM to ascertain their respective levels of precision. The proposed method can be applied to analyze many strong nonlinear oscillatory equations.
Sourav Chaudhary et al 2024 Commun. Theor. Phys. 76 055403
In this work, we have explored wormhole (WH) solutions in gravity by assuming the Morris–Thorne WH metric and , where γ is the free model parameter. We determined the WH solutions by utilizing two newly developed shape functions (SF) that satisfy all basic conditions for a WH's physical validity. We also observe that the null energy condition (NEC) behaves negatively. Finally, for both models, we use the volume integral quantifier () and Tolman–Oppenheimer–Volkoff (TOV) equation to determine how much exotic matter is needed near the WH throat and the stability of the WH. The extensive detailed discussions of the matter components have been done via graphical analysis. The obtained WH geometries meet the physically acceptable conditions for a stable wormhole.
Duo Zhang et al 2024 Commun. Theor. Phys. 76 055102
We propose a theoretical scheme to realize a two-dimensional (2D) diffraction grating in a four-level inverted-Y-type atomic system coupled by a standing-wave (SW) field and a Laguerre–Gaussian (LG) vortex field. Owing to asymmetric spatial modulation of the LG vortex field, the incident probe field can be lopsidedly diffracted into four domains and an asymmetric 2D electromagnetically induced grating is created. By adjusting the detunings of the probe field and the LG vortex field, the intensities of the LG vortex field and the coherent SW field, as well as the interaction length, the diffraction properties and efficiency, can be effectively manipulated. In addition, the effect of the azimuthal parameter on the Fraunhofer diffraction of the probe field is also discussed. This asymmetric 2D diffraction grating scheme may provide a versatile platform for designing quantum devices that require asymmetric light transmission.
Yu-Xuan Han et al 2024 Commun. Theor. Phys. 76 055404
The paper investigates the escape probability for isotropic emitters near a Kerr black hole. We propose a new approach to obtain the escape probability in a general manner, going beyond previous case-by-case studies. This approach is based on studies of the black hole shadow with astrometric observable and can be applied to emitters with an arbitrary 4-velocities and locations, even to the emitters outside of the equatorial plane. We also consider representative examples illustrating how escape probabilities vary with distance, velocity, and inclination angle. Overall, this new approach provides an effective method for studying escape probabilities near Kerr black holes.
Hai-Jun Li et al 2024 Commun. Theor. Phys. 76 055405
Supermassive black holes (SMBHs) are ubiquitous in the center of galaxies, although the origin of their massive seeds is still unknown. In this paper, we investigate the formation of SMBHs from the quantum chromodynamics (QCD) axion bubbles. In this case, primordial black holes (PBHs) are considered as the seeds of SMBHs, which are generated from the QCD axion bubbles due to an explicit Peccei–Quinn (PQ) symmetry breaking after inflation. The QCD axion bubbles are formed when the QCD axion starts to oscillate during the QCD phase transition. We consider a general case in which the axion bubbles are formed with the bubble effective angle θeff ∈ (0, π], leading to the minimum PBH mass for the axion decay constant . The PBHs at this mass region may account for the seeds of SMBHs.
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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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hong et al
The effect of magnetic gap and finite quasi-particle lifetime in topological insulator-based ferromagnet/f-wave superconductor (TI-based FM/f–wave SC) junctions is theoretically investigated by using the modified Blonder-Tinkham-Klapwijk (BTK) theory. Two types of pairings, f1 and f2–waves for SC, are considered. The results indicate that shortening the finite quasi-particle lifetime can lead to a transformation of energy-gap peaks into a zero-bias peak in tunneling conductance spectrum, as well as a transformation of energy-gap dips into a zero-bias dip in shot noise spectrum, ultimately resulting in the smoothing of both the zero-bias conductance peak and the zero-bias shot noise dip. An increase in magnetic gap can suppress tunneling conductance and shot noise when conventional Andreev retro-reflection dominates but enhance them when specular Andreev reflection is dominant. Both conventional Andreev retro-reflection and specular Andreev reflection can be enhanced by increasing quasi-particle lifetime. When Fermi energy equals the magnetic gap, tunneling conductance and shot noise values become zero across all energy ranges. These findings not only contribute to a better understanding of specular Andreev reflection in TI-based FM/f–wave SC junctions but also provide insights for experimentally determining the f-wave pairing symmetry.
Yan et al
Entanglement-breaking (EB) subspaces help determine the additivity of entanglement of formation (EOF), which is a long-standing issue in quantum information. We explicitly construct the
two-dimensional EB subspaces of any bipartite systems when system dimensions are equal, and we
apply the subspaces to construct EB spaces of arbitrary dimensions. We also present the partial
construction when system dimensions are different. Then we present the notion and properties of
EB subspaces for some systems, and in particular the absolute EB subspaces. We construct some
examples of absolute EB subspaces, as well as EB subspaces for some systems by using multiqubit
Dicke states.
Wang et al
We perform benchmark calculations of the p-wave resonances in the exponentially cosine screened Coulomb potential using the uniform complex-scaling generalized pseudospectral method. The present results show significant improvement in the calculation accuracy compared to previous predictions and correct the misidentification of resonance electron configuration in previous works. It is found that the resonance states approximately follow a n^2-scaling law which is similar to the bound counterparts. The birth of new resonance would distort the trajectory of an adjacent higher-lying resonance.
姚 et al
The Hubble tension persists as a challenge in cosmology. Even early dark energy (EDE) models, initially considered the most promising for alleviating the Hubble tension, fall short of addressing the issue without exacerbating other tensions, such as the S8 tension. Considering that a negative dark matter (DM) equation of state (EoS) parameter is conducive to reduce the value of σ8 parameter, we extend the axion-like EDE model in this paper by replacing the cold dark matter (CDM) with DM characterized by a constant EoS wdm (referred as WDM hereafter). We then impose constraints on this axion-like EDE extension model, along with three other models: the axion-like EDE model, ΛWDM, and ΛCDM. These constraints are derived from a comprehensive analysis incorporating data from the Planck 2018 cosmic microwave background (CMB), baryon acoustic oscillations (BAO), the Pantheon compilation, as well as a prior on H0 (i.e., H0=73.04±1.04, based on the latest local measurement by Riess et al.) and a Gaussianized prior on S8 (i.e., S8=0.766±0.017, determined through the joint analysis of KID1000+BOSS+2dLenS). We find that although the new model maintains the ability to alleviate the Hubble tension to ∼1.4σ, it still exacerbate the S8 tension to a level similar to that of the axion-like EDE model.
Meng et al
We present the lattice QCD simulation with the 2+1+1 flavor full QCD ensembles using near-physical quark masses and different spatial sizes $L$, at $a\sim$ 0.055 \;fm. The results show that the scalar and pesudoscalar 2-point correlator with the valence pion mass of approximately 230 MeV become degenerated at $L\le 1.0$ \;fm, and such an observation suggests that the spontaneous chiral symmetry breaking disappears effectively there. At the same time, the mass gap between the nucleon and pion masses remains larger then $\Lambda_{\rm QCD}$ at the entire $L\in[0.2,0.7]$ fm range.