• <tr id="yyy80"></tr>
  • <sup id="yyy80"></sup>
  • <tfoot id="yyy80"><noscript id="yyy80"></noscript></tfoot>
  • 99热精品在线国产_美女午夜性视频免费_国产精品国产高清国产av_av欧美777_自拍偷自拍亚洲精品老妇_亚洲熟女精品中文字幕_www日本黄色视频网_国产精品野战在线观看 ?

    Quantum dynamics of Gaudin magnets

    2022-10-22 08:14:44WenBinHeStefanoChesiHaiQingLinandXiWenGuan
    Communications in Theoretical Physics 2022年9期

    Wen-Bin He,Stefano Chesi,Hai-Qing Lin and Xi-Wen Guan

    1 Beijing Computational Science Research Center,Beijing 100193,China

    2 State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Wuhan Institute of Physics and Mathematics,APM,Chinese Academy of Sciences,Wuhan 430071,China

    3 The Abdus Salam International Center for Theoretical Physics,Strada Costiera 11,I-34151 Trieste,Italy

    4 Department of Physics,Beijing Normal University,Beijing 100875,China

    5 NSFC-SPTP Peng Huanwu Center for Fundamental Theory,Xi’an 710127,China

    6 Department of Theoretical Physics,Research School of Physics and Engineering,Australian National University,Canberra ACT 0200,Australia

    Abstract Quantum dynamics of many-body systems is a fascinating and significant subject for both theory and experiment.The question of how an isolated many-body system evolves to its steady state after a sudden perturbation or quench still remains challenging.In this paper,using the Bethe ansatz wave function,we study the quantum dynamics of an inhomogeneous Gaudin magnet.We derive explicit analytical expressions for various local dynamic quantities with an arbitrary number of flipped bath spins,such as: the spin distribution function,the spin–spin correlation function,and the Loschmidt echo.We also numerically study the relaxation behavior of these dynamic properties,gaining considerable insight into coherence and entanglement between the central spin and the bath.In particular,we find that the spin–spin correlations relax to their steady value via a nearly logarithmic scaling,where as the Loschmidt echo shows an exponential relaxation to its steady value.Our results advance the understanding of relaxation dynamics and quantum correlations of long-range interacting models of the Gaudin type.

    Keywords: Gaudin magnets,central spin model,Bethe ansatz,spin polarization,spin–spin correlation,Loschmidt echo

    1.Introduction

    Although mature paradigms,like the celebrated Fermi liquid theory [1–3]and Luttinger liquid theory [4,5],enable us to understand well a wide class of many-body systems in the stationary state,their dynamical evolution is much less understood.In fact,quantum dynamics of many-body systems always presents itself with formidable challenges,due to the difficulty of deriving eigenfunctions analytically and the exponentially growing complexity of numerics.Despite these theoretical difficulties,significant progresses have been made in the last decade,which greatly improves our understanding of dynamical properties of many-body systems.For example,the Kibble–Zurek mechanism [6]reveals power-law relations between the typical length scale ξ of defect domains,the relaxation time τ,and the rate of change of the driving parameter λ,namely ξ~λ-νand τ~λ-zν,which has been observed in ion Coulomb crystals[7].Thermalization of isolated many-body systems is also a difficult topic.The eigenstate thermalization hypothesis(ETH) [8,9]asserts that,for a closed systems evolving to the steady state,the diagonal and micro-canonical ensembles are equivalent.In recent experiments with ultracold atoms[10,11],Kinoshita et al showed that Bose gases in one-dimensional traps do not thermalize,even after thousands of collisions [12].The ETH can be violated by integrable models [13],due to the existence of infinitely many conserved charges,or in the presence of many-body localization[14].The study of dynamics is of crucial importance for many-body quantum systems out of equilibrium,as it provides important clues on if and how their equilibrium state can be reached.

    Therefore,while thermalization usually concerns the steady-state properties of many-body systems after a longtime evolution,an interesting question is on how the manybody system evolves at intermediate times.For a system with a short-range interaction,like the Heisenberg spin chain and the Lieb–Lininger model,light-cone dynamics dominates the relaxation of local observables to steady-state values,such as spin polarization and correlation functions[15].However,the relaxation process of local and global quantities to the steady state is less explored in models with long-range interactions.In this paper,we use Gaudin magnets,i.e.the inhomogeneous central spin models,to study the relaxation dynamics of many-body systems.Such magnets with long-range interactions may describe the decoherence of a spin-qubit due to the interaction with surrounding spins,for example an electron interacting with nuclear spins in quantum dots or defect centers[16,17].Quantum dynamics of the Gaudin model has been extensively studied with a variety of methods as,for example,exact diagonalization and quantum many-body expansions [17–22],the Bethe ansatz method for the polarized bath with one flipped bath spin [23],hybrid methods combining the Bethe ansatz and Monte Carlo sampling[24,25],the DMRG method and semiclassical approaches[26–29].

    Recent work described in detail the collapse and revival dynamics of the homogeneous central spin model [30],and the partition of eigenstates between entangled and separable states [31,32].

    While an early description of Gaudin magnets using the Bethe ansatz technique considered one flipped bath spin,i.e.M=1[23],here we study the time evolution of the central spin problem with an arbitrary number of flipped spins M,starting from an initial statewhere |?〉 is the fully polarized state and ai=0,1,2,...N label the positions of spins in the system.The quantum dynamics of the model with arbitrary number of flipped spins has been already studied through Bethe ansatz [24,25],as well as various other theoretical approaches,leading to important insights such as a description of quantum decoherence by the Chebyshev expansion method[33],non-Markovian dynamics[20],persistent spin correlations [34],etc.Here we study the time evolutions of several interesting quantities analytically and numerically: the spin distribution function,the spin–spin correlation function,and the Loschmidt echo.Evaluating these,we find that the time dependence of the spin polarization function reveals a breakdown of thermalization,such that the steady-state of the Gaudin magnets cannot be described by an equilibrium ensemble.Instead,the relaxation to steady-state values of the spin–spin correlation function suggests a logarithmic decay,and we find that at intermediate times the Loschmidt echo relaxes exponentially to its steady-state value,using both the Bethe ansatz solution and matrix product states (MPS) numerical approach.

    2.Model and Bethe ansatz equations

    The Gaudin magnet describes a central spin at position ‘0’coupled to bath spins through long-range interactions.The Hamiltonian reads

    where the bath spins are labelled with 1→N.For convenience,we parametrize the magnetic field as B=-2/g.Furthermore,we write Aj=1/(∈0-∈j) for the inhomogeneous interaction strength determined in experiments.Setting ∈0=0,the ∈j(with j=1,…,N)correspond to the energy levels of a discrete BCS model associated with H,which can be constructed from the conserved quantitiesHj=Bsjz+∑k≠jsj·sk(∈j-∈k) [35–37].Following the algebraic Bethe ansatz method,and considering a subspace where M spins are flipped-down with respect to the reference state |?〉,the eigenstates are given below [35,36]:

    where the M parameters{να}should satisfy the following Bethe ansatz equations

    with α=1,2,…,M.The equation (3) are also called Richardson–Gaudin equations.There areCNM+1sets of solutions to equation (3),which correspond to the number of choices of flipping M spins [38].TheseCNM+1states |ν1,…,νM〉 span the subspace with M spins flipped-down.In appendix D we give details of the numerical method for solving the Bethe Ansatz equation (3).Moreover,their eigenenergy is given by

    We exploited the above eigenfunctions to study the quantum dynamics of the central spin model.The initial state(see introduction)is a simple product state|Φ0〉=|a1,…,aM〉,where {a1,…,aM} is a set of mutually unequal site indexes which can range from‘0’to‘N’.After the interaction is switched on,the wave function evolves as

    where we introduced the orthonormalized wave functions∣φk〉=Nνk∣ν1,k,…,νM,k〉,withNνkthe normalization coeffciient7See the appendix for details.There we present brief derivations for the time evolution of the spin distribution function,the spin–spin correlation function,and the Loschmidt echo for the Gaudin magnet with arbitrary number of flipped spins M.(see appendix B).The index ‘k’ labels all the states corresponding to the roots of equation(3).Since the initial state has M spins which are flipped-down,we only need to consider the Bethe ansatz basis in this particular subspace.A critical quantity in equation (5) is the overlap between the initial state and the eigenfunctions,given as follows:

    where ‘P’means summing over all permutation of indexes{a1,…,aM},see appendices A and B.The overlap can be also written as 〈Φ0∣φk〉=Nνkperm (1/(να,k-∈Pα)),where ‘perm’is the permanent of matrix 1/(να,k-∈Pα),similar to the determinant [35,36].It is worth noting that both permanent and determinant representation can give the exact quantum dynamics of the Gaudin magnets.However,the numerical tasks from the two representations is quite different as determinants can be evaluated in polynomial time.The interested readers can find more details about permanent and determinant representations in[39–41].For either representation,it still remains challenging to get dynamical quantities for the Gaudin magnets with a large system size,and values up to N=48 were reached [24].

    From expressions (5) and (6),the evolution of observables (for example the spin distribution) can be calculated rather straightforwardly.Based on this approach,we will present in the rest of the paper our key analytical and numerical results on the quantum dynamics of Gaudin magnets.

    3.Spin distribution

    By making use of equation (5),the time-dependent polarization of site j is immediately written as

    wherewkk′=Ek′-Eksimplifies toWhile the overlaps are given in equation (6),the remaining difficulty is to obtain the matrix elements of the observable in the eigenfunction basis.As detailed in appendix B,one can insert the complete set of states |a1,…,aM〉,thus writing the matrix elements in terms of overlaps of type 〈Φ0|φk〉.We finally obtain the exact expression:

    where ,here and throughout the article,‘P’ and ‘Q’ indicate summing over all the permutations of indexes {a1,…,aM}and {j1,…,jM},respectively.

    Although it is not immediately obvious from equation (8),sjz(t) recovers the correct initial value when we take the limit t→0.Detailed proof can be found in appendix B.There we also show that,as expected,mz==(N+1)/2-Mis conserved by equation (8).The evolution of spin distribution function for a more general initial state is just an extension of above result equation (8).

    Figure 1.Time evolution of the spin polarization of individual spins,obtained from equation (3) assuming an exponentially decaying coupling constant Aj=A N exp(-j N).We take N=10 and use dimensionless units,setting A=1.In (a) (c) we choose an initial state|ΦA(chǔ)〉=|0,7,8,9,10〉.In(b)(d)the initial state is|ΦB〉=|0,2,4,6,8〉.Figures (a) and (b) present the dynamical polarization of central spins with different magnetic fields for the two initial states.Figures (c) and (d) show the dynamical evolution of bath spins at B=0.5 for the two initial states.

    We have evaluated equation(8)for two representative initial conditions,i.e.the domain-wall stateand the anti-ferromagnetically ordered stateand present in figure 1 the resulting polarization of individual spins.The dynamical evolution of the central spin is shown in panels(a)and(b),and is allowed by the interaction with the bath spins,which leads to change of the orientation of the central spin through flip-flop processes.It is characterized by a quick decay to the steady-state value,with the persistence of an oscillatory behavior due to finite-size effects [24].There is a competition between magnetic field and coupling to the bath spins,evident from the evolution curves at different values of B shown in figures 1(a) and (b).The physical mechanism behind the suppressed evolution at large B is the increase of the energy gap between states with s0z=± 1/2,which inhibits changes of orientation of the central spin.In appendix C,we also present the detailed derivation of the reduced density matrix and von Neumann entropy for the central spin.The general behavior of the central spin polarization in figure 1 is very similar to the oscillatory time dependence observed for the von Neumann entropy,see figure 7.

    For models with short-range interactions,it is wellknown that the time-evolution of non-equilibrium states is characterized by a light-cone dynamics of local observables[42–45].On the other hand,the Gaudin magnets is a longrange model and,as shown in figures 1(c) and (d),the spin polarization of the bath spins evolve simultaneously into their steady-state value.Being infinite-range,the interaction of the Gaudin magnet can take effect without any propagation time.

    Comparing the two initial states,we see that with |ΦA(chǔ)〉the bath spins need a much longer time than |ΦB〉 to evolve into a steady state.In fact,for the initial state |ΦA(chǔ)〉 the two groups of bath spins remain well distinct,and the oscillation in the spin polarization nearly approach periodically their initial values (1/2 or-1/2).On the other hand,the polarizations for the initial state |ΦB〉 show an initial quick decay,leading to oscillations around 0.The evolution for the initial state|ΦA(chǔ)〉displays a strong memory of the initial domain-wall order.In order to further understand such peculiar dynamics,in later sections we will study the time evolution of the spin–spin correlations and the Loschmidt echo.

    Figure 2.(a)Time average of the central spin polarization,computed for different values of B and N=10.The solid lines are for the initial state |ΦA(chǔ)〉 while the dashed lines are for the initial state |ΦB〉.(b) Dependence of -(i.e.the difference in the time-averaged central spin polarization between the two initial conditions) on the bath spin number N.Here we use a fixed value of B=0.5.The red circles are from the exact Bethe ansatz equations,where as the blue diamonds are obtained by the matrix product state (MPS) method(see section 4).

    4.Spin–spin correlations

    The spin–spin correlation function is defined asGmzn(t)=〈ψ(t)∣smzsnz∣ψ(t)〉and,as discussed in appendix B,which can be computed in a way similar to the spin density.The explicit expression reads:

    which characterizes longitudinal correlation between spins.

    In figure 3,we show the spin–spin correlation function at different times,both for the initial state|ΦA(chǔ)〉(left panels)and|ΦB〉 (right panels).On a relatively short timescale (t<50),the correlation function is very similar to t=0 for both initial states and when the evolution time approaches t~102the correlation function has decreased to smaller values.However,it can be noted that in the left panels of figure 3(referring to|ΦA(chǔ)〉),the domain-wall order has not faded away completely even after a long evolution time t~103.This is in contrast to panel (h) on the right side,where the anti-ferromagnetic alignment has nearly disappeared.This confirms our previous observation that the domain-wall configuration is more favourable to retain memory of the initial state(see also figure 5 for the Loschmidt echo).

    From the contour plot of the correlations in figure 3,the correlations between the bath spins Gmznwith m,n >0 tend to zero.Meanwhile the correlations between the central spin and bath spinsGmz0with m >0 oscillate near initial value.After long enough time evolution (t~103),the correlations between the bath spins almost evolve toward to zero for the state |ΦB〉.

    Considering in more detail the right side of figure 3,we see in panel (g) that the correlations Gmznwith m,n ?5 are more robust,and also the values ofGnz0with larger n remain rather similar to the initial values.This behavior is a consequence of the small coupling strength Ajwhen j is large,which implies a longer timescale for those bath spins.However,after a sufficiently long time evolution (t~103) the correlations between all spins are close to zero.The vanishing of correlations in panel (h) indicates that the steady state is like a paramagnetic state.

    To further analyze the evolution ofGmzn(t),we characterize the typical correlation strength for spin m as

    where the self-correlation terms Gmzmare excluded.In figure 4,we show the absolute value of correlation function and the typical correlation strength for the two initial states,i.e.the left two panels(a),(c)are for the initial state|ΦA(chǔ)〉and the right two panels (b),(d) for |ΦB〉.For both ferromagnetic and anti-ferromagnetic alignment,the correlation strength decays from initial maximum value of 1/4 towards smaller values,with Tm=0 corresponding to disordered spin alignment.We can see that there are two stages in the relaxation of correlations.After the initial decay (up to t10,see the first black dash line),there is an intermediate regime in which the correlation strength has a logarithmic relaxation (up to t~102,near the second black dash line),i.e. ΔTm∝-lnt.In this interval the linear decay shown in figure 4 (on a semilogarithmic scale) has its steepest slope.Finally,in the longtime limit the central spin is strongly entangled with bath spins and the value of Tmreaches its steady-state value.Due to finite-size effects,the decay is modified by oscillations,see especially panel (b),but the qualitative form and timescales are quite robust with respect to the value of m and the type of initial state.

    Figure 3.Left panels: the spin–spin correlation functionGmzm at different times,with a bath size N=10,magnetic field B=0.5,and initial state |ΦA(chǔ)〉=|0,7,8,9,10〉.Right panels: spin–spin correlation functionGmzm with the initial state |ΦB〉=|0,2,4,6,8〉.

    Figure 4.Panels (a) and (b) plot the spin–spin correlation function∣G0 zn∣for spins n=1,N.Panels (c) and (d) average the spin–spin correlation function according to equation (10).The bath size is N=10 and the magnetic field B=0.5.Left panels: initial state|ΦA(chǔ)〉=|0,7,8,9,10〉.Right panels: initial state |ΦB〉=|0,2,4,6,8〉.

    5.Loschmidt echo and MPS approach

    The Loschmidt echo,defined as L(t)=|〈Φ0|ψ(t)〉|2,quantifies the memory of the initial state [46],thus can provide us a clear understanding of the difference between the evolution for the two initial states.By using equation (5),we express L(t) as:

    where the overlaps are given in equation (6).Finally,we obtain:

    We show representative examples of the Loschmidt echo in figure 5.As seen in panel (a),for a weak magnetic field(B~0.5) the initial state |ΦA(chǔ)〉 leads to a long-time evolution with large oscillations around a mean value(t)~0.25.Instead,panel (b) shows that L(t)~0 in the long-time limit,thus the system nearly loses its memory of the initial state|ΦB〉.

    In the first part of the time evolution,besides the presence of fast small amplitude oscillations,the Loschmidt echo displays a clear exponential dependence ΔL(t) ∝exp(-γt),up to an intermediate time scale t~102.According to our numerical calculation,the decay coefficients are similar for both initial states,i.e.γA?γB~0.03 with B=0.5.Such exponential scaling behavior of the Loschmidt echo has been widely found in dynamical evolution of quantum many-body system [47–50].

    Figure 5.Time dependence of the Loschmidt echo for two different initial state.Panel (a) with the initial state |ΦA(chǔ)〉,and panel (b) with initial state |ΦB〉.

    In order to confirm the scaling relaxation behavior of Loschmidt echo for a larger system size,we further perform an approximate calculation based on the MPS method[51,52],as implemented in the Itensor library[53].There are two important input parameters of the MPS simulations: the variational tolerance ∈ of the MPS wavefunction,which represents the error of the MPS state in approximating the true wavefunction (we use ∈=10-9in our simulations),and the bond dimension χ,which indicates the maximum dimension of the matrices entering the variational ansatz.In the given implementation of the MPS method,the bond dimension is automatically increased to meet the desired tolerance.In figure 6,we show the Loschmidt echo for a bath size N=50 and the two types of initial states considered in this work,|ΦA(chǔ)〉 (red lines) and |ΦB〉 (cyan lines).Also in this case the Loschmidt echo is characterized by an initial exponential decay,and this behavior persists up to intermediate times(t ≈102).

    Unfortunately,we are not able to access the long-time dynamics at N=50 based on the MPS approach,as the entanglement in the wavefunction grows with time.This reflects itself on a rapid increase of the bond dimension χ,which eventually reaches numerically intractable values.The time dependence of χ in the simulation of figure 6 is shown in the inset.As seen,the bond dimension χ of initial state |ΦB〉grows faster in time than |ΦA(chǔ)〉.Nevertheless,the range of times we can simulate is sufficient to establish conclusively the initial exponential form of decay of Loschmidt echo.In classical systems,the exponential decay of Loschmidt echo usually implies chaotic dynamics[49,54,55].For the central spin model,the exponential decay of Loschmidt echo may indicate the dynamics is chaotic here as well [56].

    Figure 6.Loschmidt echo as function of time t for two different initial states by using an MPS method with N=50.The red line is for the initial states|ΦA(chǔ)〉,and the cyan line is for the initial state|ΦB〉.

    6.Conclusion

    In summary,based on Bethe Anstaz techniques,we have analytically studied the time evolution of several dynamic quantities of Gaudin magnets with arbitrary number M of flipped-down spins,such as spin distribution function,spin–spin correlation function,and Loschmidt echo.Furthermore,we have numerically studied the scaling behavior of the relaxation dynamics,up to relatively large system sizes.Significantly,the correlation function relaxes to its steady value with a logarithmic dependence,and the Loschmidt echo reveals an exponential loss of the memory of the initial state.Our results highlight several interesting features of the dynamical evolution of a quantum many-body system with long range interactions,thus advancing the understanding of decoherence for single qubits coupled to a spin bath at the many-body level.With respect to universal features of quantum many-body systems,much effort is still necessary to better understand the non-equilibrium quantum dynamics[57].In future studies,it would be desirable to extend our methods to investigate scrambling in many-body system[58,59],and the out-of-time-of-correlation function (OTOC)[60]of central-spin models.The details of such dynamical evolution of spin correlations may be accessible experimentally,e.g.through NMR techniques [61].

    Acknowledgments

    We would like to thank R Fazio for useful discussions and F Iemini and D Ferreira their kind help with the MPS simulation package.WBH acknowledges support from NSAF(Grant No.U1930402).XWG is supported by the key NSFC grant No.12134015 and No.11 874 393,and the National Key R&D Program of China No.2017YFA0304500.SC acknowledges support from NSFC (Grants No.11 974 040 and No.12150610464)and the National Key R&D Program of China No.2016YFA0301200.HQL acknowledges financial support from National Science Association Funds U1930402 and NSFC 11 734 002,as well as computational resources from the Beijing Computational Science Research Center.

    Appendix A.Bethe ansatz basis

    The eigenstates of equation (1) can be obtained with Bethe ansatz(BA)approach,as discussed in detail in[36].Here we discuss several properties of these states which will find wide use in the following derivations.Since the Hilbert space of the Gaudin model can be decomposed into the direct sum of subspaces with M flipped-down spins,we introduce two basis sets for such subspaces.One is the natural basisand another is the Bethe ansatz basisThe corresponding completeness relations are simply given by:

    where ∣Nνk∣are the normalization coefficients for the Bethe ansatz basis.The two sets of states |j1,…,jM〉 and |ν1,k,…,νM,k〉are both complete in the subspace with M flipped-down spins.Including all the M,the complete basis of the whole Hilbert space is obtained.

    The explicit form of the Bethe ansatz eigenfunctions reads

    where ,as in the main text,Q are the permutations of indexes{j1,…,jM}.Note also that any of the two ‘j’ indexes are necessarily unequal.The overlap of state |a1,…,aM〉 with a BA eigenstate|ν1,k,…,νM,k〉can be simply obtained from the above expression as:

    where P are the permutations of indexes {a1,…,aM}.The above formula can be also written in terms of the permanent of the matrix[40].

    The scalar product between eigenstates can be obtained by insertion of

    where we used the overlaps equation (A4) between the two basis sets.The above expression gives the normalization coefficient ∣Nνk∣2.

    We can also derive another useful formula:

    which is obtained by inserting the resolution of the identity in terms of the BA eigenstates.

    Appendix B.Evaluation of physical observables

    We now discuss the explicit evaluation of equation(7),where we recall that∣φk〉=Nνk∣ν1,k,…,νM,k〉are the normalized eigenfunctions.Therefore,for an initial state in the form∣Φ0〉=sa-1…sa-M∣?〉=∣a1,…,aM〉,the overlap matrix elements 〈Φ0|φk〉 are immediately found from equation (A4),and are given in equation (6).Instead,to compute the matrix element ofsjz,we use the fact that such operator is diagonal in the natural basis |j1,…,jM〉 and:

    By inserting the completeness relation in terms of the|j1,…,jM〉states,and computing the overlaps with eigenstates|φk〉as in equation (6),it is easy to find that:

    Finally,combining overlaps and matrix element gives:

    In the above formulas,as usual,P are permutations of the indexes {a1,…,aM} (from the initial state) andQ are permutations of the indexes {j1,…,jM}.The term proportional to 1/2 (from the parenthesis in the first line) can be further simplified as follows.First we note that this term contains a factor of type equation (A5),which is∝δkk′.Therefore,we can simply set coswkk′t=1in this particular contribution.After noticing this,we can use equation (A6) to perform the summations over k andk′ and finally recover the 1/2 appearing in equation (8) of the main text.

    Using a similar method,we can derive the spin–spin correlation function,given by

    While the overlaps are found in equation (6),the matrix elements ofsmzsnzcan be obtained in a way completely analogous to equation (B2):

    leading to equation (9) in the main text.

    Finally,we discuss how to recover the initial conditions,and prove the conservation of magnetization.When time t→0,the spin distribution becomes

    which is in a form suitable to equation (A6).Performing the summations over k andk′ we get:

    which recovers the initial spin distribution.For the total magnetization,computingmz=∑j sjz(t) leads to∑j,αδjjα=Min the second term of equation(7).Finally,the summation overk,k′ can be computed as discussed after equation (B3),leading to the expected result mz=(N+1)/2-M.

    Appendix C.Reduced density matrix of the central spin

    The density matrix ρs=|ψ(t)〉〈ψ(t)| is given by

    Figure C1.Time dependence of the von Neumann entropy at different magnetic fields.Upper subplot:initial state|ΦA(chǔ)〉=|0,7,8,9,10〉.Lower subplot: initial state |ΦB〉=|0,2,4,6,8〉.

    where ,by using equation (A3):

    HereR indicates the permutations of {l1,…,lM}.

    Now we consider the reduced density matrix of central spin,defined byρcs=Tr1→N[ρs].With our choice of initial state,there are no off-diagonal elements and the result is in the form:

    The first contribution arises from the terms of equation (C2)where ji=li>0 (i.e.site 0 is not flipped) and A(t) has the following expression:

    The second contribution corresponds to j1=l1=0 (i.e.the central spin is flipped) and D(t) reads:

    With the help of equations (A5) and (A6),we can prove A+D=1.The von Neumann entropy is simply given asS=-AlnA-DlnD,and a representative plot is shown in figure C1.

    Appendix D.Numerical method for solving BA roots

    In our work we solve the BA equations (3) using the numerical method presented in [38].For convenience of the reader,in this appendix we present the numerical method in detail.For general M,the asymptotic solution to equation (3)with g→0 reads:

    We then introduce the quantities

    and transform Eq.(3) to the following form:

    The advantage of using the Λjvariables is in avoiding the singular dependence of ναon system parameters.With να(0)as initial value,we use Newtonian iteration to find the solution of the above equations at fixed g.

    After obtaining Λj,the νjcan be found as follows.We first transform equation (D2) into

    The above equation (D4) gives a linear system in thepivariables:

    which are elementary symmetric polynomials of the BA parameters ναand p0can be defined as 1.Finally,after obtaining the values of piwe consider the Mth-order polynomial:

    whose zeroes give the desired BA parameters να.An example of the dependence of the BA parameters {ν}on g is shown in figure D1.Close to g=0 the BA parameters ν are all real,but complex conjugate pairs are formed by neighboring roots at larger values of|g|.The interested reader can also see[38]for the description of this method.

    Figure D1.Dependence of BA parameters on g.The top (bottom)panel shows the real (imaginary) part.System parameters: N=15,M=8,and A=2.

    国产人伦9x9x在线观看 | 青春草亚洲视频在线观看| 最新的欧美精品一区二区| 国产日韩欧美在线精品| 人妻人人澡人人爽人人| 多毛熟女@视频| 日韩人妻精品一区2区三区| 日韩,欧美,国产一区二区三区| 久久久精品区二区三区| 侵犯人妻中文字幕一二三四区| av天堂久久9| 亚洲精品久久久久久婷婷小说| 国产精品一区二区在线观看99| 91成人精品电影| 国产爽快片一区二区三区| 国产一级毛片在线| 我要看黄色一级片免费的| 久久精品久久精品一区二区三区| 免费不卡的大黄色大毛片视频在线观看| 哪个播放器可以免费观看大片| 国产女主播在线喷水免费视频网站| 亚洲av电影在线进入| 黄色一级大片看看| 亚洲经典国产精华液单| 丁香六月天网| 中文字幕制服av| 五月天丁香电影| 美女xxoo啪啪120秒动态图| 亚洲情色 制服丝袜| 欧美另类一区| 成人国语在线视频| 人成视频在线观看免费观看| 香蕉丝袜av| 国产不卡av网站在线观看| 热re99久久精品国产66热6| 夜夜骑夜夜射夜夜干| 亚洲色图综合在线观看| 日韩大片免费观看网站| 成人国产麻豆网| 男人操女人黄网站| 午夜福利在线观看免费完整高清在| h视频一区二区三区| 赤兔流量卡办理| 国产精品久久久av美女十八| 欧美成人精品欧美一级黄| 免费在线观看视频国产中文字幕亚洲 | av女优亚洲男人天堂| 啦啦啦视频在线资源免费观看| 一级片免费观看大全| videosex国产| 高清视频免费观看一区二区| 人妻 亚洲 视频| 伊人久久国产一区二区| 啦啦啦啦在线视频资源| 免费黄网站久久成人精品| 精品国产超薄肉色丝袜足j| 国产免费一区二区三区四区乱码| 亚洲国产精品一区三区| 啦啦啦在线观看免费高清www| 日本vs欧美在线观看视频| 欧美日韩视频精品一区| 男女边摸边吃奶| 丝袜美腿诱惑在线| 色网站视频免费| 亚洲国产精品一区二区三区在线| 国产成人精品福利久久| 亚洲av电影在线进入| 色网站视频免费| 亚洲一码二码三码区别大吗| 日韩av在线免费看完整版不卡| 电影成人av| 你懂的网址亚洲精品在线观看| 九草在线视频观看| 久久av网站| 热99久久久久精品小说推荐| 欧美在线黄色| 高清在线视频一区二区三区| 中文字幕亚洲精品专区| 老熟女久久久| 秋霞伦理黄片| 欧美日韩一区二区视频在线观看视频在线| 精品国产一区二区久久| 啦啦啦在线观看免费高清www| 久久久久久久精品精品| 人妻人人澡人人爽人人| 男男h啪啪无遮挡| 国产免费一区二区三区四区乱码| 一级毛片我不卡| 婷婷成人精品国产| 天天影视国产精品| 欧美日本中文国产一区发布| 性高湖久久久久久久久免费观看| 欧美日韩一区二区视频在线观看视频在线| 交换朋友夫妻互换小说| 超色免费av| 免费播放大片免费观看视频在线观看| 大码成人一级视频| 91精品伊人久久大香线蕉| 日韩制服骚丝袜av| 自拍欧美九色日韩亚洲蝌蚪91| 一级片免费观看大全| 91aial.com中文字幕在线观看| 在线精品无人区一区二区三| 国产一区有黄有色的免费视频| 午夜影院在线不卡| 亚洲欧美日韩另类电影网站| 亚洲精品国产av成人精品| 国产1区2区3区精品| 日韩三级伦理在线观看| 少妇的丰满在线观看| 午夜福利网站1000一区二区三区| 亚洲在久久综合| 午夜福利在线免费观看网站| 日本欧美视频一区| 国产不卡av网站在线观看| 欧美成人精品欧美一级黄| 亚洲av免费高清在线观看| 下体分泌物呈黄色| 欧美精品av麻豆av| 99久久综合免费| 欧美bdsm另类| 在线精品无人区一区二区三| 久久久a久久爽久久v久久| 免费在线观看视频国产中文字幕亚洲 | 亚洲精品aⅴ在线观看| 只有这里有精品99| 亚洲欧美成人综合另类久久久| 成人国语在线视频| 亚洲精品国产一区二区精华液| 亚洲情色 制服丝袜| 午夜老司机福利剧场| 亚洲国产精品成人久久小说| 亚洲一区中文字幕在线| 韩国av在线不卡| 如何舔出高潮| 婷婷色av中文字幕| 国产亚洲av片在线观看秒播厂| 18+在线观看网站| 在线天堂中文资源库| 美女大奶头黄色视频| 中文欧美无线码| 亚洲国产欧美在线一区| 天美传媒精品一区二区| av女优亚洲男人天堂| 少妇猛男粗大的猛烈进出视频| 中国国产av一级| a级毛片黄视频| 亚洲av免费高清在线观看| 久久久久久免费高清国产稀缺| 巨乳人妻的诱惑在线观看| 大香蕉久久网| 边亲边吃奶的免费视频| 成人国产麻豆网| 最近中文字幕高清免费大全6| 少妇猛男粗大的猛烈进出视频| 丝袜脚勾引网站| 香蕉精品网在线| 久久久a久久爽久久v久久| 女人久久www免费人成看片| 久久久久久久久久久久大奶| 精品国产乱码久久久久久小说| 亚洲av男天堂| 日本av手机在线免费观看| 亚洲综合精品二区| 一本久久精品| 国产老妇伦熟女老妇高清| 欧美成人午夜精品| 久久久精品区二区三区| av在线app专区| 精品亚洲成a人片在线观看| 男女午夜视频在线观看| 亚洲精华国产精华液的使用体验| 免费在线观看完整版高清| 十八禁网站网址无遮挡| 国产精品不卡视频一区二区| 在线精品无人区一区二区三| 国产成人一区二区在线| 国产午夜精品一二区理论片| 看十八女毛片水多多多| 日本-黄色视频高清免费观看| 汤姆久久久久久久影院中文字幕| 中文欧美无线码| 大片电影免费在线观看免费| av在线播放精品| 中文字幕精品免费在线观看视频| 国产欧美日韩一区二区三区在线| 在线天堂中文资源库| 午夜日本视频在线| 国产欧美日韩综合在线一区二区| 亚洲国产av影院在线观看| 精品一区在线观看国产| 国语对白做爰xxxⅹ性视频网站| 国产精品一二三区在线看| 日本91视频免费播放| 亚洲在久久综合| 黄频高清免费视频| 男女啪啪激烈高潮av片| 亚洲美女视频黄频| 亚洲精品乱久久久久久| 有码 亚洲区| 国产高清国产精品国产三级| 日本爱情动作片www.在线观看| 国语对白做爰xxxⅹ性视频网站| 麻豆乱淫一区二区| 日韩一区二区视频免费看| 午夜日本视频在线| 中文字幕最新亚洲高清| 啦啦啦视频在线资源免费观看| 热99国产精品久久久久久7| 999久久久国产精品视频| 久久精品国产亚洲av涩爱| 国产av精品麻豆| 国产免费福利视频在线观看| 日韩中字成人| 男女高潮啪啪啪动态图| 91精品伊人久久大香线蕉| 亚洲欧美日韩另类电影网站| 亚洲国产成人一精品久久久| 男人添女人高潮全过程视频| 久久国产精品大桥未久av| 国产极品天堂在线| 国产男女内射视频| 国产成人av激情在线播放| 侵犯人妻中文字幕一二三四区| 中文字幕制服av| 人人妻人人爽人人添夜夜欢视频| 国产欧美亚洲国产| 久久精品久久久久久噜噜老黄| 毛片一级片免费看久久久久| 亚洲婷婷狠狠爱综合网| 精品少妇内射三级| 又黄又粗又硬又大视频| 99热全是精品| 精品视频人人做人人爽| 看免费成人av毛片| 久久99精品国语久久久| 国产成人91sexporn| 97在线视频观看| 亚洲综合精品二区| 亚洲精品第二区| 精品一品国产午夜福利视频| 久久精品人人爽人人爽视色| 久久精品亚洲av国产电影网| 色哟哟·www| 亚洲国产最新在线播放| 建设人人有责人人尽责人人享有的| 午夜福利视频在线观看免费| 欧美xxⅹ黑人| 免费av中文字幕在线| 热re99久久国产66热| 国产黄色视频一区二区在线观看| 丁香六月天网| 日本免费在线观看一区| 亚洲综合色惰| 久久97久久精品| 黄色视频在线播放观看不卡| 天天躁狠狠躁夜夜躁狠狠躁| 不卡视频在线观看欧美| 亚洲人成77777在线视频| 国产精品久久久久久久久免| 久久精品人人爽人人爽视色| 亚洲综合色惰| 欧美日韩视频高清一区二区三区二| 妹子高潮喷水视频| 日本黄色日本黄色录像| 精品人妻偷拍中文字幕| 亚洲av电影在线观看一区二区三区| 黄色毛片三级朝国网站| 国产深夜福利视频在线观看| 女人久久www免费人成看片| 亚洲精品aⅴ在线观看| 成年女人毛片免费观看观看9 | 午夜日韩欧美国产| av线在线观看网站| 国产成人精品在线电影| 亚洲欧洲国产日韩| 伦理电影免费视频| 不卡av一区二区三区| 国产成人精品一,二区| 99国产精品免费福利视频| 久久99精品国语久久久| 亚洲国产精品一区三区| 免费黄网站久久成人精品| 黄色一级大片看看| 亚洲av男天堂| 久久午夜福利片| 国产爽快片一区二区三区| 亚洲久久久国产精品| 青草久久国产| 中文字幕av电影在线播放| 久久久精品区二区三区| 亚洲久久久国产精品| 亚洲精品日韩在线中文字幕| 欧美少妇被猛烈插入视频| 2021少妇久久久久久久久久久| 国产一区有黄有色的免费视频| 成人免费观看视频高清| 国产极品粉嫩免费观看在线| 免费观看无遮挡的男女| 亚洲欧美色中文字幕在线| 久久久久久久久久人人人人人人| 亚洲美女视频黄频| 久久午夜综合久久蜜桃| 国产精品嫩草影院av在线观看| 国产亚洲av片在线观看秒播厂| www.av在线官网国产| 久久精品久久久久久噜噜老黄| 日韩成人av中文字幕在线观看| 最近2019中文字幕mv第一页| 国产av一区二区精品久久| 久久久亚洲精品成人影院| 亚洲,欧美,日韩| 久久精品亚洲av国产电影网| 有码 亚洲区| 亚洲成人一二三区av| 久久久久久久久久人人人人人人| 可以免费在线观看a视频的电影网站 | 免费黄频网站在线观看国产| 国产一区二区激情短视频 | 国产97色在线日韩免费| 黄片播放在线免费| 精品少妇一区二区三区视频日本电影 | 久久久久精品久久久久真实原创| 99九九在线精品视频| 免费黄网站久久成人精品| 日韩精品免费视频一区二区三区| 热99久久久久精品小说推荐| 亚洲精品美女久久久久99蜜臀 | 亚洲熟女精品中文字幕| 亚洲美女视频黄频| 2018国产大陆天天弄谢| 热re99久久国产66热| 秋霞在线观看毛片| 日日啪夜夜爽| 欧美精品人与动牲交sv欧美| 国产97色在线日韩免费| 春色校园在线视频观看| 亚洲伊人色综图| 成年女人在线观看亚洲视频| 美女脱内裤让男人舔精品视频| 国产免费福利视频在线观看| 亚洲美女视频黄频| 最近中文字幕高清免费大全6| 欧美人与性动交α欧美软件| 一级爰片在线观看| 成人毛片60女人毛片免费| 一本色道久久久久久精品综合| 亚洲欧美精品综合一区二区三区 | 国产av码专区亚洲av| 亚洲成国产人片在线观看| 一区二区三区乱码不卡18| 在线精品无人区一区二区三| 色吧在线观看| 999精品在线视频| 最近中文字幕2019免费版| av免费在线看不卡| 亚洲精品日本国产第一区| 少妇的逼水好多| 丝袜人妻中文字幕| 午夜91福利影院| 久久狼人影院| 国产精品国产三级专区第一集| 91精品国产国语对白视频| tube8黄色片| 电影成人av| 黄片播放在线免费| 男女午夜视频在线观看| 纵有疾风起免费观看全集完整版| 国产片内射在线| av在线app专区| 日本-黄色视频高清免费观看| 在线观看国产h片| 亚洲伊人色综图| 精品福利永久在线观看| 九九爱精品视频在线观看| 夫妻性生交免费视频一级片| 一级毛片电影观看| 亚洲少妇的诱惑av| 久久99蜜桃精品久久| 久久午夜福利片| 久久这里有精品视频免费| 最新的欧美精品一区二区| 搡老乐熟女国产| 黑人巨大精品欧美一区二区蜜桃| 午夜福利在线免费观看网站| 久久久国产一区二区| 久热久热在线精品观看| 天堂中文最新版在线下载| 伦理电影免费视频| 婷婷色av中文字幕| 久久女婷五月综合色啪小说| 成人国产av品久久久| 日本91视频免费播放| a级毛片在线看网站| 久久综合国产亚洲精品| 久久久久久久国产电影| 最近中文字幕2019免费版| 国产男人的电影天堂91| 亚洲精品成人av观看孕妇| 亚洲精品一二三| 哪个播放器可以免费观看大片| 国产精品久久久久久av不卡| 久久久a久久爽久久v久久| 交换朋友夫妻互换小说| 久久午夜综合久久蜜桃| 国产爽快片一区二区三区| 久久人妻熟女aⅴ| av一本久久久久| 国产日韩欧美视频二区| 国产欧美亚洲国产| 精品久久久久久电影网| 亚洲国产精品成人久久小说| 1024香蕉在线观看| 中文字幕人妻熟女乱码| 免费在线观看视频国产中文字幕亚洲 | 美女国产高潮福利片在线看| 宅男免费午夜| 国产极品粉嫩免费观看在线| 免费日韩欧美在线观看| 宅男免费午夜| 亚洲av男天堂| 少妇人妻精品综合一区二区| 久久久久久久久久人人人人人人| 久久久国产一区二区| 婷婷成人精品国产| 免费女性裸体啪啪无遮挡网站| 成人漫画全彩无遮挡| 99久久人妻综合| 1024视频免费在线观看| 嫩草影院入口| av视频免费观看在线观看| 99香蕉大伊视频| 天天躁日日躁夜夜躁夜夜| 深夜精品福利| 各种免费的搞黄视频| 在线观看www视频免费| 丝袜美腿诱惑在线| 9色porny在线观看| 天天躁狠狠躁夜夜躁狠狠躁| av在线观看视频网站免费| 精品卡一卡二卡四卡免费| 一级爰片在线观看| 久久精品亚洲av国产电影网| 又黄又粗又硬又大视频| 亚洲成av片中文字幕在线观看 | 国产av国产精品国产| 国产精品久久久av美女十八| 成年av动漫网址| 叶爱在线成人免费视频播放| av一本久久久久| 久久精品国产鲁丝片午夜精品| 亚洲av中文av极速乱| 久久午夜福利片| 国产午夜精品一二区理论片| 精品一区二区三区四区五区乱码 | 国产精品久久久av美女十八| 久久99蜜桃精品久久| 美国免费a级毛片| 欧美激情 高清一区二区三区| 少妇人妻久久综合中文| 精品少妇一区二区三区视频日本电影 | 色视频在线一区二区三区| 国产又爽黄色视频| av免费观看日本| 中文乱码字字幕精品一区二区三区| 国产精品二区激情视频| 免费不卡的大黄色大毛片视频在线观看| 黄网站色视频无遮挡免费观看| 久久久久久久久久人人人人人人| 青春草亚洲视频在线观看| 免费黄频网站在线观看国产| 两性夫妻黄色片| 我要看黄色一级片免费的| 99re6热这里在线精品视频| av又黄又爽大尺度在线免费看| 国产一级毛片在线| 国产成人精品无人区| 好男人视频免费观看在线| 久久久精品免费免费高清| 婷婷色综合大香蕉| 99热全是精品| 香蕉丝袜av| 啦啦啦在线免费观看视频4| 精品人妻在线不人妻| 国产麻豆69| 亚洲欧美日韩另类电影网站| 亚洲国产日韩一区二区| 亚洲成国产人片在线观看| 精品亚洲乱码少妇综合久久| 午夜福利在线观看免费完整高清在| 亚洲情色 制服丝袜| 男女无遮挡免费网站观看| 99热网站在线观看| 如何舔出高潮| 只有这里有精品99| 人妻少妇偷人精品九色| 国产视频首页在线观看| 一级爰片在线观看| 国产精品秋霞免费鲁丝片| 亚洲精品中文字幕在线视频| 中文天堂在线官网| 99九九在线精品视频| 久久久久精品人妻al黑| www.精华液| 久久久a久久爽久久v久久| 视频区图区小说| 妹子高潮喷水视频| 亚洲av中文av极速乱| 精品少妇一区二区三区视频日本电影 | 少妇猛男粗大的猛烈进出视频| kizo精华| 国产男女内射视频| 亚洲精品一区蜜桃| 欧美日韩精品成人综合77777| 亚洲精品第二区| av网站免费在线观看视频| 一区二区三区乱码不卡18| 久久久久国产网址| 久久综合国产亚洲精品| 亚洲精品一二三| 亚洲欧洲日产国产| 国产亚洲精品第一综合不卡| 91国产中文字幕| 狂野欧美激情性bbbbbb| 99精国产麻豆久久婷婷| 校园人妻丝袜中文字幕| 欧美人与善性xxx| 成人影院久久| 精品一区二区三卡| 国产精品人妻久久久影院| av线在线观看网站| 久久精品久久久久久噜噜老黄| 亚洲精品在线美女| 视频在线观看一区二区三区| 热99国产精品久久久久久7| 老司机影院毛片| 国精品久久久久久国模美| 久久这里有精品视频免费| 精品久久蜜臀av无| 欧美成人午夜免费资源| 男人操女人黄网站| 国产日韩欧美视频二区| 成人毛片60女人毛片免费| 一本大道久久a久久精品| 国产精品av久久久久免费| 久久韩国三级中文字幕| 国产在线视频一区二区| 美女xxoo啪啪120秒动态图| 日韩一区二区视频免费看| 国产一区亚洲一区在线观看| 飞空精品影院首页| 亚洲精品,欧美精品| 国产乱来视频区| 一级,二级,三级黄色视频| 水蜜桃什么品种好| 国产福利在线免费观看视频| 夜夜骑夜夜射夜夜干| 欧美最新免费一区二区三区| 一二三四中文在线观看免费高清| 岛国毛片在线播放| 亚洲,一卡二卡三卡| 十八禁网站网址无遮挡| 黄片播放在线免费| 看免费成人av毛片| 亚洲 欧美一区二区三区| 99国产精品免费福利视频| 观看美女的网站| 欧美+日韩+精品| 久久 成人 亚洲| 在线天堂中文资源库| xxxhd国产人妻xxx| 亚洲精品美女久久久久99蜜臀 | 午夜福利一区二区在线看| 亚洲内射少妇av| 久久婷婷青草| 夫妻午夜视频| 国产片特级美女逼逼视频| 曰老女人黄片| 黄频高清免费视频| 国产成人a∨麻豆精品| 亚洲国产日韩一区二区| 日日爽夜夜爽网站| 国产在线免费精品| 国产免费视频播放在线视频| 一级毛片黄色毛片免费观看视频| 男人爽女人下面视频在线观看| 久久久亚洲精品成人影院| 三级国产精品片| 国产极品粉嫩免费观看在线| 极品少妇高潮喷水抽搐| 免费久久久久久久精品成人欧美视频| 少妇的逼水好多| 日本爱情动作片www.在线观看| 久久久久久久久久人人人人人人| 女性被躁到高潮视频| 亚洲欧美成人综合另类久久久| 丝瓜视频免费看黄片| 中文字幕色久视频| 男女午夜视频在线观看| 亚洲av男天堂| 久久久国产欧美日韩av| 国产男女内射视频| 亚洲,欧美,日韩| 国产1区2区3区精品| 精品国产乱码久久久久久男人| 国产精品嫩草影院av在线观看| 午夜福利网站1000一区二区三区| 最近的中文字幕免费完整| 黄片无遮挡物在线观看| 国产爽快片一区二区三区| 日韩一卡2卡3卡4卡2021年| 国产精品久久久av美女十八| 亚洲成国产人片在线观看| 成年女人在线观看亚洲视频| 激情五月婷婷亚洲|