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.
Open all abstracts, in this tab
Zhiyuan Wang et al 2023 Commun. Theor. Phys. 75 015101
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.
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.
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.
Qing-Zhen Chai et al 2024 Commun. Theor. Phys. 76 065301
By using potential energy surface (PES) calculations in the three-dimensional space (β2, γ, β4) within the framework of the macroscopic-microscopic model, the fission trajectory and fission barrier for Z = 118(Og), 119, 120 nuclei has been systematically investigated. The calculated PES includes macroscopic liquid-drop energy, microscopic shell correction and pairing correction. Taking the 294Og176 nucleus as an example, we discuss the next closed shell after Z = 82 and N = 126 with the calculated Woods–Saxon single-particle levels. Then, the results of PES in 294Og is illustrated from the (X, Y) scale to the (β2, γ) scale. The γ degree of freedom reveals the shape evolution clearly during the fission process. The structure near the minimum and saddle point of the PES in the Z = 118, 119, 120 nuclei is demonstrated simultaneously. Based on the potential energy curves, general trends of the evolution of the fission barrier heights and widths are also studied. The triaxial deformation in these superheavy mass regions plays a vital role in the first fission barrier, showing a significant reduction in both triaxial paths. In addition, the model-dependent fission barriers of proton-rich nuclei 295Og, 296119, and 297120 are analyzed briefly. Our studies could be valuable for synthesizing the superheavy new elements in the forthcoming HIAF and other facilities.
Xiuyuan Yang et al 2021 Commun. Theor. Phys. 73 047601
The drying of liquid droplets is a common daily life phenomenon that has long held a special interest in scientific research. When the droplet includes nonvolatile solutes, the evaporation of the solvent induces rich deposition patterns of solutes on the substrate. Understanding the formation mechanism of these patterns has important ramifications for technical applications, ranging from coating to inkjet printing to disease detection. This topical review addresses the development of physical understanding of tailoring the specific ring-like deposition patterns of drying droplets. We start with a brief introduction of the experimental techniques that are developed to control these patterns of sessile droplets. We then summarize the development of the corresponding theory. Particular attention herein is focused on advances and issues related to applying the Onsager variational principle (OVP) theory to the study of the deposition patterns of drying droplets. The main obstacle to conventional theory is the requirement of complex numerical solutions, but fortunately there has been recent groundbreaking progress due to the OVP theory. The advantage of the OVP theory is that it can be used as an approximation tool to reduce the high-order conventional hydrodynamic equations to first-order evolution equations, facilitating the analysis of soft matter dynamic problems. As such, OVP theory is now well poised to become a theory of choice for predicting deposition patterns of drying droplets.
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.
Li Miao et al 2011 Commun. Theor. Phys. 56 525
We review the problem of dark energy, including a survey of theoretical models and some aspects of numerical studies.
Xiong Zhao and Yongge Ma 2024 Commun. Theor. Phys. 76 065403
We propose a new gravitational theory with torsion based on Riemann–Cartan geometry, in which all physical quantities are dynamical. In addition to the spacetime metric, the gravitational degrees of freedom in this theory also include the torsion and two scalar fields. The energy-momentum tensor of the matter fields in this theory is also proposed. A spherically symmetric static vacuum solution of the theory is obtained. It turns out that this solution can fit the observational data of the rotation curve outside the stellar disk in the Milky Way. Therefore, the galactic dark matter may just be the gravitational effect of the theory with torsion.
Open all abstracts, in this tab
Xiong Zhao and Yongge Ma 2024 Commun. Theor. Phys. 76 065403
We propose a new gravitational theory with torsion based on Riemann–Cartan geometry, in which all physical quantities are dynamical. In addition to the spacetime metric, the gravitational degrees of freedom in this theory also include the torsion and two scalar fields. The energy-momentum tensor of the matter fields in this theory is also proposed. A spherically symmetric static vacuum solution of the theory is obtained. It turns out that this solution can fit the observational data of the rotation curve outside the stellar disk in the Milky Way. Therefore, the galactic dark matter may just be the gravitational effect of the theory with torsion.
Haryanto M Siahaan 2024 Commun. Theor. Phys. 76 065402
In this study, we investigate ModMax electrodynamics localized within the Randall–Sundrum II and Dvali–Gabadadze–Porrati branes, deriving corresponding 3-brane spacetime solutions that conform to the effective Einstein equations in each specific scenario. We construct solutions for charged black holes within the effective Einstein equation framework in both braneworld scenarios. The examination explores the trajectories of charged objects in this spacetime, underscoring the significance of the nonlinear parameter. Our analysis uncovers the fact that, similar to the prior ModMax black hole investigation, the nonlinear parameter plays a pivotal role in suppressing the effective charge of the black hole, due to its definite positive value.
Adnan Malik et al 2024 Commun. Theor. Phys. 76 065005
The aim of this work is to investigate anisotropic compact objects within the framework of f(G) modified theory of gravity. For our present work, we utilize Krori–Barua metrics, i.e., λ(r) = Xr2 + Y and β(r) = Zr2. We use some matching conditions of spherically symmetric spacetime with Bardeen's model as an exterior geometry. Further, we establish some expressions of energy density and pressure components to analyze the stellar configuration of Bardeen compact stars by assuming viable f(G) models. We examine the energy conditions for different stellar structures to verify the viability of our considered models. Moreover, we also investigate some other physical features, such as equilibrium condition, equation of state parameters, adiabatic index, stability analysis, mass function, surface redshift, and compactness factor, respectively. It is worthwhile to mention here for the current study that our stellar structure in the background of Bardeen's model is more viable and stable.
Yu-Hao Wang et al 2024 Commun. Theor. Phys. 76 065006
Exact analytical solutions are good candidates for studying and explaining the dynamics of solitons in nonlinear systems. We further extend the region of existence of spin solitons in the nonlinearity coefficient space for the spin-1 Bose–Einstein condensate. Six types of spin soliton solutions can be obtained, and they exist in different regions. Stability analysis and numerical simulation results indicate that three types of spin solitons are stable against weak noise. The non-integrable properties of the model can induce shape oscillation and increase in speed after the collision between two spin solitons. These results further enrich the soliton family for non-integrable models and can provide theoretical references for experimental studies.
Xiaofei Qi et al 2024 Commun. Theor. Phys. 76 065103
A quantum network concerns several independent entangled resources and can create strong quantum correlations by performing joint measurements on some observers. In this paper, we discuss an n-partite chain network with each of two neighboring observers sharing an arbitrary Bell state and all intermediate observers performing some positive-operator-valued measurements with parameter λ. The expressions of all post-measurement states between any two observers are obtained, and their quantifications of Bell nonlocality, Einstein–Podolsky–Rosen steering and entanglement with different ranges of λ are respectively detected and analyzed.
Open all abstracts, in this tab
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.
Open all abstracts, in this tab
Cheng et al
Collective quantum states, such as subradiant and superradiant states, are useful for controlling optical responses in many-body quantum systems. In this work, we study novel collective quantum phenomena in waveguide-coupled Bragg atom arrays with inhomogeneous frequencies. For atoms without free-space dissipation, collectively induced transparency is produced by destructive quantum interference between subradiant and superradiant states. In a large Bragg atom array, multi-frequency photon transparency can be obtained by considering atoms with different frequencies. Interestingly, we find collectively induced absorption (CIA) by studying the influence of free-space dissipation on photon transport. Tunable atomic frequencies nontrivially modify decay rates of subradiant states. When the decay rate of a subradiant state equals to the free-space dissipation, photon absorption can reach a limit at a certain frequency. In other words, photon absorption is enhanced with low free-space dissipation, distinct from previous photon detection schemes. We also show multi-frequency CIA by properly adjusting atomic frequencies. Our work presents a way to manipulate collective quantum states and exotic optical properties in waveguide QED systems.
Liu et al
Ultracold atoms endowed with tunable spin-orbital-angular-momentum coupling (SOAMC) represent a promising avenue for delving into exotic quantum phenomena. Building on recent experimental advancements, we propose the generation of synthetic gauge fields and including exotic vortex phases within spinor Bose-Einstein condensates, employing a combination of a running wave and Laguerre-Gaussian laser fields. We investigate the ground-state characteristics of the SOAMC condensate, revealing the emergence of exotic vortex states with controllable orbital angular momenta. It is shown that the interplay of the SOAMC and conventional spin-linear-momentum coupling (SLMC) induced by the running wave beam, leads to the formation of vortex state exhibiting phase stripe hosting single multiply quantized singularity. The phase of the ground state will undergo the phase transition phase corresponding to the breaking of rotational symmetry while preserving the mirror symmetry. Importantly, the observed density distribution of ground state wavefunction, exhibiting broken rotational symmetry can be well characterized by the synthetic magnetic field generated through light interaction with the dressed spin state. Our findings pave the way for further exploration into the rotational properties of stable, exotic vortices with higher orbital angular momenta against splitting in the presence of synthetic gauge fields in ultracold quantum gases.
yanyan
We conducted a study on a simplified dark matter (DM) model that introduces a vector-like intermediate particle, facilitating exclusive interactions between DM and the top quark in the Standard Model (SM). The analysis focused on the relic density of Dirac-type fermion DM and highlighted the complementary role of direct detection (DD) in constraining the DM model. Notably, in instances when DM mass is small, the tree-level two-body annihilation process experiences suppression. In such scenarios, the contributions of the three-body process and the one-loop process dominate the relic abundance. Concerning DD, calculations were performed for the two-loop contribution to the DM-gluon interaction, yielding the corresponding spin-independent scattering cross-section.
Frutos-Alfaro
Approximate all-terrain spacetimes for astrophysical applications are presented. The metrics possess five relativistic multipole moments,
namely mass, rotation, mass quadrupole, charge, and magnetic dipole moment. All these spacetimes approximately satisfy the Einstein-
Maxwell field equations. The first metric is generated by means of the Hoenselaers-Perjés method from given relativistic multipoles. The
second metric is a perturbation of the Kerr-Newman metric, which makes it a relevant approximation for astrophysical calculations. The
last metric is an extension of the Hartle-Thorne metric that is important for obtaining internal models of compact objects perturbatively.
The electromagnetic field is calculated using Cartan forms for locally nonrotating observers. These spacetimes are relevant to infer properties of compact objects from astrophysical observations. Furthermore, the numerical implementations of these metrics are straightforward, making them versatile for simulating the potential astrophysical applications.
Wang et al
The third harmonic generation (THG) coefficient for the spherical quantum dot (QD) system with Inversely Quadratic Hellmann Plus Inversely Quadratic Potential (IQHIQP) is investigated theoretically, considering the regulation of the quantum size, confinement potential depth and external environment. The numerical simulation results indicate that the THG coefficient can reach the order of 10-12 m2/V2, which strongly relies on the tunable factor, with its resonant peak experiencing a red-shift or blue-shift. Interestingly, the effect of temperature on the THG coefficient in terms of peak location and size is consistent with the quantum dot radius but contrasts with the hydrostatic pressure. Thus, it is crucial to focus on the influence of internal and external parameters on nonlinear optical effects, and to implement the theory in practical experiments and the manufacture of optoelectronic devices.