1,721,024 research outputs found
Relaxation of the order-parameter statistics in the Ising quantum chain
Full text linkWe study the out-of-equilibrium probability distribution function of the local order parameter in the transverse field Ising quantum chain. Starting from a fully polarised
state, the relaxation of the ferromagnetic order is analysed: we obtain a full analytical
description of the late-time stationary distribution by means of a remarkable relation
to the partition function of a 3-states classical model. Accordingly, depending on the
phase whereto the post-quench Hamiltonian belongs, the probability distribution may
locally retain memories of the initial long-range order. When quenching deep in the
broken-symmetry phase, we show that the stationary order-parameter statistics is indeed related to that of the ground state. We highlight this connection by inspecting the
ground-state equilibrium properties, where we propose an effective description based
on the block-diagonal approximation of the n-point spin correlation functions
Off-equilibrium relaxational dynamics with an improved Ising Hamiltonian
No full textWe study the off-equilibrium relaxational dynamics at criticality in the three-dimensional Blume–Capel model whose static critical behaviour belongs to the 3D Ising universality class. Using an 'improved' Hamiltonian (the leading corrections to scaling have vanishing amplitude) we perform Monte Carlo simulations of the relaxational dynamics after a quench from T=infinity to Tc. Analysing the off-equilibrium dynamics at Tc we obtain an estimate of the dynamical critical exponent z = 2.020(8) that is perfectly consistent with the field theory predictions
Nonstabilizerness via Perfect Pauli Sampling of Matrix Product States
Full text linkWe introduce a novel approach to evaluate the nonstabilizerness of an N-qubits matrix product state (MPS) with bond dimension χ. In particular, we consider the recently introduced stabilizer Rényi entropies (SREs). We show that the exponentially hard evaluation of the SREs can be achieved by means of a simple perfect sampling of the many-body wave function over the Pauli string configurations. The sampling is achieved with a novel MPS technique, which enables us to compute each sample in an efficient way with a computational cost O(Nχ^{3}). We benchmark our method over randomly generated magic states, as well as in the ground-state of the quantum Ising chain. Exploiting the extremely favorable scaling, we easily have access to the nonequilibrium dynamics of the SREs after a quantum quench
Thermalization of long range Ising model in different dynamical regimes: a full counting statistics approach
Full text linkWe study thermalization of transverse field Ising chain with power law
decaying interaction following a global quantum quench of
the transverse field to two different dynamical regimes. We quantify the
thermalization behavior by comparing the full probability distribution function
(PDF) of the evolving states with the corresponding thermal state given by the
Gibbs canonical ensemble (GCE). To this end, we use matrix product state (MPS)
based time dependent variational principle (TDVP) algorithm to simulate both
real time evolution following a global quantum quench and the finite
temperature density operator. We observe that thermalization is strongly
suppressed in the region with strong confinement for all the interaction
strength considered whereas thermalization occurs in the region with
weak confinement.Comment: 25 pages, 5 figures in main tex
Real-time-dynamics quantum simulation of (1+1)-dimensional lattice QED with Rydberg atoms
Full text linkWe show how to implement a Rydberg-atom quantum simulator to study the nonequilibrium dynamics of an Abelian (1+1)-dimensional lattice gauge theory. The implementation locally codifies the degrees of freedom of a Z3 gauge field, once the matter field is integrated out by means of the Gauss local symmetries. The quantum simulator scheme is based on currently available technology and thus is scalable to considerable lattice sizes. It allows, within experimentally reachable regimes, us to explore different string dynamics and to infer information about the Schwinger U(1) model
Entanglement evolution across defects in critical anisotropic Heisenberg chains
No full textWe study the out-of-equilibrium time evolution after a local quench connecting two anisotropic spin-1/2 XXZ Heisenberg open chains via an impurity bond. The dynamics is obtained by means of the adaptive time-dependent density-matrix renormalization group. We show that the entanglement entropies (von Neumann and Renyi) in the presence of a weakened bond depend on the sign of the bulk interaction. For an attractive interaction (Delta < 0), the defect turns out to be irrelevant and the evolution is asymptotically equivalent to the one without defect obtained by conformal field theory. For a repulsive interaction (Delta > 0), the defect is relevant and the entanglement saturates to a finite value. This out-of-equilibrium behavior generalizes the well-known results for the ground-state entanglement entropy of the model
How order melts after quantum quenches
Full text linkInjecting a sufficiently large energy density into an isolated many-particle system prepared in a state with long-range order will lead to the melting of the order over time. Detailed information about this process can be derived from the quantum mechanical probability distribution of the order parameter. We study this process for the paradigmatic case of the spin-1/2 Heisenberg XXZ chain. We determine the full quantum mechanical distribution function of the staggered subsystem magnetization as a function of time after a quantum quench from the classical Néel state. We establish the existence of an interesting regime at intermediate times that is characterized by a very broad probability distribution. Based on our findings we propose a simple general physical picture of how long-range order melts
Thermalization propagation front and robustness against avalanches in localized systems
No full textWe investigate the robustness of the many-body localized (MBL) phase to the quantum-avalanche instability by studying the dynamics of a localized spin chain coupled to a T=∞ thermal bath through its leftmost site. By analyzing local magnetizations we estimate the size of the thermalized sector of the chain and find that it increases logarithmically slowly in time. This logarithmically slow propagation of the thermalization front allows us to lower-bound the slowest thermalization time, and find a broad parameter range where it scales fast enough with the system size that MBL is robust against thermalization induced by avalanches. The further finding that the imbalance - a global quantity measuring localization - thermalizes over a timescale that is exponential both in disorder strength and system size is in agreement with these results
Non-equilibrium transport in d-dimensional non-interacting Fermi gases
No full textAbstract. We consider a non-interacting Fermi gas in d dimensions, both in the non-relativistic and relativistic case. The system of size Ld is initially prepared into two halves L and R, each of them thermalized at two different temperatures, TL and TR respectively. At time t = 0 the two halves are put in contact and the entire system is left to evolve unitarily. We show that, in the thermodynamic limit, the time evolution of the particle and energy densities is perfectly described by a semiclassical approach which permits to analytically evaluate the correspondent stationary currents. In particular, in the case of non-relativistic fermions, we find a low-temperature behavior for the particle and energy currents which is independent from the dimensionality d of the system, being proportional to the difference T 2L − T 2R. Only in one spatial dimension (d = 1), the results for the non-relativistic case agree with the massless relativistic ones. 1
Full counting statistics as probe of measurement-induced transitions in the quantum Ising chain
Full text linkNon-equilibrium dynamics of many-body quantum systems under the effect of
measurement protocols is attracting an increasing amount of attention. It has
been recently revealed that measurements may induce different non-equilibrium
regimes and an abrupt change in the scaling-law of the bipartite entanglement
entropy. However, our understanding of how these regimes appear, how they
affect the statistics of local quantities and, finally whether they survive in
the thermodynamic limit, is much less established. Here we investigate
measurement-induced phase transitions in the Quantum Ising chain coupled to a
monitoring environment. In particular we show that local projective
measurements induce a quantitative modification of the out-of-equilibrium
probability distribution function of the local magnetization. Starting from a
GHZ state, the relaxation of the paramagnetic and the ferromagnetic order is
analysed. In particular we describe how the probability distribution of the
former shows different behaviour in the area-law and volume-law regimes
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