Structural properties of Li atom under quantum and classical plasmas: A composite variational framework

Structural properties of 1s²nl (²L) [n = 2–5, l = 0–4; where, n and l are the principal quantum number and orbital angular momentum quantum number, respectively] states of Li atom embedded in classical weakly coupled plasma (WCP) and dense quantum plasma (DQP) have been discussed. The Debye-Hckel potential or the screened-Coulomb potential (SCP) and exponential-cosine-screened Coulomb potential (ECSCP) have been used to mimic the WCP and DQP, respectively. Li atom has been treated as a composite system with a frozen core Li⁺ ion and a chemically active valence electron. The Rayleigh-Ritz variational method with Hylleraas-type basis set has been used to estimate the energy eigenvalue of 1s² (¹S) state of Li⁺ ion core and a pure exponential basis has been considered to compute the energy of nl (²L) states of the valence electron of Li atom. The influence of ECSCP and SCP on the radial probability distribution of the valence electron of the Li atom has also been studied.     

Time optimal control of two-level quantum systems

The objective of time-optimal control that helps to minimize relaxation losses, is the evolution of a quantum state from a given initial mixed state to a final target mixed state in minimum time. In this paper, we study a time-optimal control problem of the dynamic of a pure two-level system with unbounded control using Pontryagin's minimum principle and obtain the minimal time for some initial and final states. The results will apply to basically all qubit systems that one can consider such as NMR spectroscopy, trapped ions, superconducting qubits, etc. We also show that these results hold for pure states, and only the direction $\hat{n}$ is important in the evolution of a quantum state. In this work, the problem of computing minimum time to produce any unitary transformation $U_f\in SU(2)$ is reduced to finding the minimum time to steer the system from an initial to a final state.     

Hidden measurement model for pure and mixed states of quantum physics in Euclidean space

We propose a representation of quantum mechanics where all pure and mixed states of a n-dimensional quantum entity are represented as points of a subset of an ²-dimensional real space. We introduce the general measurements of quantum mechanics on this entity, determined by sets of mutual orthogonal points of the representation space. Within this framework we construct a hidden measurement model for an arbitrary finite dimensional quantum entity.     

Tighter Weighted Polygamy Inequalities of Multipartite Entanglement in Arbitrary-Dimensional Quantum Systems

We investigate polygamy relations of multipartite entanglement in arbitrary-dimensional quantum systems. By improving an inequality and using the βth (0 ≤ β ≤ 1) power of entanglement of assistance, we provide a new class of weighted polygamy inequalities of multipartite entanglement in arbitrary-dimensional quantum systems. We show that these new polygamy relations are tighter than the ones given in Kim (Phys. Rev. A 97, 042332 2018).

     

Pairwise entanglement in symmetric multi-qubit systems

For pairs of particles extracted from a symmetric state of N two-level systems, the two-particle density matrix is expressed in terms of expectation values of collective spin operators for the large system. Results are presented for experimentally relevant examples of pure states: Dicke states | S, M>, spin coherent, and spin squeezed states, where only the symmetric subspace, S = N/2 is populated, and for thermally entangled mixed states populating also lower S values. The entanglement of the extracted pair is then quantified by a calculation of the concurrence, which provides directly the entanglement of formation of the pair. Received 9 May 2001 and Received in final form 16 November 2001     

Pure operations and measurements

States of a quantum system may be influenced by an external intervention. FollowingHaag andKastler, such a transformation of states is called an operation, and is called pure if it transforms pure states into pure states. Operations are discussed here under the assumption that they are caused by interactions with another system (apparatus), described by aS matrix. Pure operations are then shown to correspond, with one exception, to operatorsA with norm smaller than one. The Hermitean operatorsF=A*A represent quantum effects as defined axiomatically byLudwig. The particular case of local operations in quantum field theory is also investigated.Supported in part by the Deutsche Forschungsgemeinschaft.     

Electron Correlations and Classification Schemes for Intershell Doubly Excited States

High-lying intershell doubly excited states of He and H⁻ are studied and energies and intrinsic characteristics of their wave functions are reported. Results for energies of ³S and ¹P^e doubly excited states associated with the hydrogenic manifold up to N = 20 are presented and compared to available data from the literature. The classification of these doubly excited states by approximate quantum numbers is reexamined.     

Abundance of translation invariant pure states on quantum spin chains

We construct a set of translation invariant pure states of a quantum spin chain, which is w -dense in the set of all translation invariant states of the chain. Each of the approximating states has exponential decay of correlations, and is the unique ground state of a finite range Hamiltonian with a spectral gap above the ground state energy.     

Transport through artificial single-molecule magnets: Spin-pair state sequential tunneling and Kondo effects

The transport properties of an artificial single-molecule magnet based on a CdTe quantum dot doped with a single Mn+2 ion(S=5/2) are investigated by the non-equilibrium Green function method.We consider a minimal model where the Mn-hole exchange coupling is strongly anisotropic so that spin-flip is suppressed and the impurity spin S and a hole spin s entering the quantum dot are coupled into spin pair states with(2S+1) sublevels.In the sequential tunneling regime,the differential conductance exhibits(2S+1) possible peaks,corresponding to resonance tunneling via(2S+1) sublevels.At low temperature,Kondo physics dominates transport and(2S+1) Kondo peaks occur in the local density of states and conductance.These peaks originate from the spin-singlet state formed by the holes in the leads and on the dot via higher-order processes and are related to the parallel and antiparallel spin pair states.     

Cryptanalysis and Improvement of a Multiparty Quantum Direct Secret Sharing of Classical Messages with Bell States and Bell Measurements

Recently, a multiparty quantum direct secret sharing protocol with Bell states was presented (Song et al., Int. J Theor. Phys. 57, 1559, 2018). In this protocol, the secret message of the dealer is directly encoding into the transmitted particles. All agents obtain their pieces of secret by making Bell state measurement on their receiving particles, then cooperate to recover the dealer’s secret. However, as we show, this protocol is insecure, because an outside attacker or two special dishonest agents can eavesdrop the secret fully. Furthermore, an improved version of this protocol is proposed, which can stand against the presented attacks.

     

L 2-Cohomology of Hyperkähler Quotients

Using an argument of Jost and Zuo, we give a criterion which implies that the L ² harmonic forms on a complete noncompact hyperk?hler manifold lie in the middle dimension and are invariant under the isometry group. This is applied to various examples, and in particular gives a verification of some of the predictions of Sen on monopole moduli spaces. Received: 20 September 1999 / Accepted: 2 November 1999     

Quantum cobwebs: Universal entangling of quantum states

Entangling an unknown qubit with one type of reference state is generally impossible. However, entangling an unknown qubit with two types of reference states is possible. To achieve this, we introduce a new class of states called zero sum amplitude (ZSA) multipartite, pure entangled states for qubits and study their salient features. Using shared-ZSA states, local operations and classical communication, we give a protocol for creating multipartite entangled states of an unknown quantum state with two types of reference states at remote places. This provides a way of encoding an unknown pure qubit state into a multiqubit entangled state.     

Spin States of Iron-Nitrosyl Adsorption Complexes Formed in Fe-ZSM5 Zeolites

The capability of extra-framework monoiron sites to adsorb up to three NO molecules has been proven by quantum chemical calculations. Spin states of iron-nitrosyl adsorption complexes formed in Fe-ZSM5 zeolites have been found. For an initial iron site with S = 2, successive adsorption of one, two and three NO molecules changes S to 3/2, 1 and 1/2, respectively. Thus, the electron paramagnetic resonance (EPR) S = 1/2 signal observed after NO adsorption on the Fe-ZSM5 catalyst may be assigned to the Fe²⁺(NO)₃ species. Some peculiarities of the S = 1/2 EPR spectra obtained for iron-nitrosyl species in zeolites are discussed. Authors' address: Sergey E. Malykhin, Boreskov Institute of Catalysis, Russian Academy of Sciences, Prospect Lavrentieva 5, Novosibirsk 630090, Russian Federation     

Transition Moments betweenΔg,Πg, andΠuStates of the H2Molecule

Electronic transition moments are computed for dipole transitions between theCandD¹Π_u,IandR¹Π_gandJandS¹Δ_gstates of the hydrogen molecule for internuclear distancesR∈ [1, 15] bohr. The character of the wavefunctions at large internuclear distances is investigated. It is shown that in theDandRstates the asymptotic configurations are strongly mixed forR≤ 15 bohrs. TheSstate has mixed character even atR= 40 bohr.     

Counterexamples to the Maximal p-Norm Multiplicativity Conjecture for all p > 1

The quantum marginal problem asks what local spectra are consistent with a given spectrum of a joint state of a composite quantum system. This setting, also referred to as the question of the compatibility of local spectra, has several applications in quantum information theory. Here, we introduce the analogue of this statement for Gaussian states for any number of modes, and solve it in generality, for pure and mixed states, both concerning necessary and sufficient conditions. Formally, our result can be viewed as an analogue of the Sing-Thompson Theorem (respectively Horn’s Lemma), characterizing the relationship between main diagonal elements and singular values of a complex matrix: We find necessary and sufficient conditions for vectors (d ₁,..., d _n ) and (c ₁,..., c _n ) to be the symplectic eigenvalues and symplectic main diagonal elements of a strictly positive real matrix, respectively. More physically speaking, this result determines what local temperatures or entropies are consistent with a pure or mixed Gaussian state of several modes. We find that this result implies a solution to the problem of sharing of entanglement in pure Gaussian states and allows for estimating the global entropy of non-Gaussian states based on local measurements. Implications to the actual preparation of multi-mode continuous-variable entangled states are discussed. We compare the findings with the marginal problem for qubits, the solution of which for pure states has a strikingly similar and in fact simple form.     

Limited Resource Semi-Quantum Secret Sharing Based on Multi-Level Systems

In the actual quantum task, it is more realistic to achieve the same task with quantum resources as few as possible which is known as semi-quantum idea. This paper proposed a novel and resultful semi-quantum secret sharing protocol, which is implemented using product states based on multi-level systems. In this scheme, the quantum capabilities of the receivers Bob and Charlie are limited, and the sender Alice does not have to access quantum memory. In addition, the security of the protocol is analyzed in detail from two aspects of Intercept-measure-resend and Entangle-measuring attacks initiated by internal malicious participants. More importantly, among the premise of proximate security of Ref. Li et al. (Quantum Inf. Process. 17, 285, 2018), our scheme reduces the number of particles used for eavesdropping detection and increases the amount of information carried by each particle.

     

Population of the states in collisions of mixed-state (1s21S,1s2s3S) B3+ and C4+ ion beams with He and H2 targets

Auger KLn lines are observed in high-resolution electron spectra obtained in collisions of mixed-state (1s²¹S,1s2s³S) He-like beams of 4 MeV B³⁺ with H₂ and 6 MeV C⁴⁺ with He targets. Supporting atomic structure calculations show these lines to correspond to doubly excited states, which can be readily populated by electron transfer to the component of the mixed-state beam. They thus provide indirect evidence for the existence of the corresponding KLn quartet states, similarly produced, even though their weak Auger decay does not allow for their direct observation in the electron spectra. These KLn quartet states mostly decay in a cascade chain of strong radiative E1 transitions, eventually terminating at the state, which is thus additionally enhanced. An upper limit on the state population due to cascades is obtained by assuming a statistical production of KLn quartet to doublet states followed by a 100% cascade feeding of the state. Our estimated upper limit is supported by our absolute cross section measurements and corresponding three-electron atomic orbital close coupling calculations in progress. Results to date are presented and discussed.