scholarly journals Novel quantum phase transition from bounded to extensive entanglement

2017 ◽  
Vol 114 (20) ◽  
pp. 5142-5146 ◽  
Author(s):  
Zhao Zhang ◽  
Amr Ahmadain ◽  
Israel Klich
Keyword(s):  
Phase Transition ◽  
Quantum Phase Transition ◽  
Ground States ◽  
Quantum Correlations ◽  
Quantum Phase ◽  
Continuous Family ◽  
Many Body ◽  
Many Body Systems ◽  
Special Circumstances ◽  
Area Law

The nature of entanglement in many-body systems is a focus of intense research with the observation that entanglement holds interesting information about quantum correlations in large systems and their relation to phase transitions. In particular, it is well known that although generic, many-body states have large, extensive entropy, ground states of reasonable local Hamiltonians carry much smaller entropy, often associated with the boundary length through the so-called area law. Here we introduce a continuous family of frustration-free Hamiltonians with exactly solvable ground states and uncover a remarkable quantum phase transition whereby the entanglement scaling changes from area law into extensively large entropy. This transition shows that entanglement in many-body systems may be enhanced under special circumstances with a potential for generating “useful” entanglement for the purpose of quantum computing and that the full implications of locality and its restrictions on possible ground states may hold further surprises.

scholarly journals Entanglement entropy in quasi-symmetric multi-qubit states

2015 ◽  
Vol 13 (02) ◽  
pp. 1550007 ◽  
Author(s):  
Zhi-Hua Li ◽  
An-Min Wang
Keyword(s):  
Phase Transition ◽  
Quantum Phase Transition ◽  
Entanglement Entropy ◽  
Ground States ◽  
Quantum Phase ◽  
Transition Points ◽  
Qubit States ◽  
Basis Vectors ◽  
Dicke States

We generalize the symmetric multi-qubit states to their q-analogs, whose basis vectors are identified with the q-Dicke states. We study the entanglement entropy in these states and find that entanglement is extruded towards certain regions of the system due to the inhomogeneity aroused by q-deformation. We also calculate entanglement entropy in ground states of a related q-deformed Lipkin–Meshkov–Glick (LMG) model and show that the singularities of entanglement can correctly signify the quantum phase transition points for different strengths of q-deformation.

scholarly journals Classical and Quantum Signatures of Quantum Phase Transitions in a (Pseudo) Relativistic Many-Body System

2020 ◽  
Vol 5 (2) ◽  
pp. 26
Author(s):  
Maximilian Nitsch ◽  
Benjamin Geiger ◽  
Klaus Richter ◽  
Juan-Diego Urbina
Keyword(s):  
Phase Transition ◽  
Quantum Phase Transition ◽  
Quantum Phase Transitions ◽  
Mean Field ◽  
Finite Size ◽  
Quantum Phase ◽  
Effective Model ◽  
Field Analysis ◽  
Many Body ◽  
Linear Dispersion

We identify a (pseudo) relativistic spin-dependent analogue of the celebrated quantum phase transition driven by the formation of a bright soliton in attractive one-dimensional bosonic gases. In this new scenario, due to the simultaneous existence of the linear dispersion and the bosonic nature of the system, special care must be taken with the choice of energy region where the transition takes place. Still, due to a crucial adiabatic separation of scales, and identified through extensive numerical diagonalization, a suitable effective model describing the transition is found. The corresponding mean-field analysis based on this effective model provides accurate predictions for the location of the quantum phase transition when compared against extensive numerical simulations. Furthermore, we numerically investigate the dynamical exponents characterizing the approach from its finite-size precursors to the sharp quantum phase transition in the thermodynamic limit.

scholarly journals Entanglement Entropy and Quantum Phase Transition in the O(N) σ-model

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Jiunn-Wei Chen ◽  
Shou-Huang Dai ◽  
Jin-Yi Pang
Keyword(s):  
Phase Transition ◽  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Quantum Phase Transition ◽  
Entanglement Entropy ◽  
Quantum Phase ◽  
Leading Order ◽  
Coupling Constant ◽  
Area Law ◽  
Conformal Scalar Field

Abstract We investigate how entanglement entropy behaves in a non-conformal scalar field system with a quantum phase transition, by the replica method. We study the σ-model in 3+1 dimensions which is O(N) symmetric as the mass squared parameter μ2 is positive, and undergoes spontaneous symmetry breaking while μ2 becomes negative. The area law leading divergence of the entanglement entropy is preserved in both of the symmetric and the broken phases. The spontaneous symmetry breaking changes the subleading divergence from log to log squared, due to the cubic interaction on the cone. At the leading order of the coupling constant expansion, the entanglement entropy reaches a cusped maximum at the quantum phase transition point μ2 = 0, and decreases while μ2 is tuned away from 0 into either phase.

Quantum correlations in Heisenberg XY spin-1 and spin-1/2 model with Dzyaloshinskii–Moriya interactions

2015 ◽  
Vol 13 (05) ◽  
pp. 1550035 ◽  
Author(s):  
Wajid Hussain Joyia
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quantum Phase Transition ◽  
Quantum Correlation ◽  
Quantum Discord ◽  
Quantum Correlations ◽  
Spin Systems ◽  
Quantum Phase ◽  
Xy Model ◽  
Higher Spin

We study the quantum correlations in a spin-1/2 (qubit) and spin-1 (qutrit) Heisenberg XY model separately, based on quantum discord (QD) and measurement-induced disturbance (MID) respectively. We find the evidence of the first- and second-order quantum phase transition (QPT) in both spin-1/2 and spin-1 systems. The effect of the temperature, magnetic field and Dzyaloshinskii–Moriya (DM) interactions on QPT and quantum correlation are also investigated. Finally, we observed that the QD and MID are not only vigorous for higher spin systems but also more robust than entanglement.

scholarly journals Observation of a quantum phase transition in the quantum Rabi model with a single trapped ion

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
M.-L. Cai ◽  
Z.-D. Liu ◽  
W.-D. Zhao ◽  
Y.-K. Wu ◽  
Q.-X. Mei ◽  
...  
Keyword(s):  
Phase Transition ◽  
Thermodynamic Limit ◽  
Quantum Phase Transitions ◽  
Paul Trap ◽  
Single Mode ◽  
Quantum Phase ◽  
Controlled Study ◽  
Many Body ◽  
Rabi Model ◽  
Many Body Systems

AbstractQuantum phase transitions (QPTs) are usually associated with many-body systems in the thermodynamic limit when their ground states show abrupt changes at zero temperature with variation of a parameter in the Hamiltonian. Recently it has been realized that a QPT can also occur in a system composed of only a two-level atom and a single-mode bosonic field, described by the quantum Rabi model (QRM). Here we report an experimental demonstration of a QPT in the QRM using a 171Yb+ ion in a Paul trap. We measure the spin-up state population and the average phonon number of the ion as two order parameters and observe clear evidence of the phase transition via adiabatic tuning of the coupling between the ion and its spatial motion. An experimental probe of the phase transition in a fundamental quantum optics model without imposing the thermodynamic limit opens up a window for controlled study of QPTs and quantum critical phenomena.

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