scholarly journals Particle entanglement in continuum many-body systems via quantum Monte Carlo

2014 ◽  
Vol 89 (14) ◽  
Author(s):  
C. M. Herdman ◽  
P.-N. Roy ◽  
R. G. Melko ◽  
A. Del Maestro
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Many Body ◽  
Many Body Systems

scholarly journals Sign-Problem-Free Fermionic Quantum Monte Carlo: Developments and Applications

2019 ◽  
Vol 10 (1) ◽  
pp. 337-356 ◽  
Author(s):  
Zi-Xiang Li ◽  
Hong Yao
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Hot Spot ◽  
High Temperature Superconductors ◽  
System Size ◽  
Many Body ◽  
Broken Symmetries ◽  
Sign Problem ◽  
Universal Quantum ◽  
Many Body Systems

Reliable simulations of correlated quantum systems, including high-temperature superconductors and frustrated magnets, are increasingly desired nowadays to further our understanding of essential features in such systems. Quantum Monte Carlo (QMC) is a unique numerically exact and intrinsically unbiased method to simulate interacting quantum many-body systems. More importantly, when QMC simulations are free from the notorious fermion sign problem, they can reliably simulate interacting quantum models with large system size and low temperature to reveal low-energy physics such as spontaneously broken symmetries and universal quantum critical behaviors. Here, we concisely review recent progress made in developing new sign-problem-free QMC algorithms, including those employing Majorana representation and those utilizing hot-spot physics. We also discuss applications of these novel sign-problem-free QMC algorithms in simulations of various interesting quantum many-body models. Finally, we discuss possible future directions of designing sign-problem-free QMC methods.

scholarly journals Easing the Monte Carlo sign problem

2020 ◽  
Vol 6 (33) ◽  
pp. eabb8341 ◽  
Author(s):  
Dominik Hangleiter ◽  
Ingo Roth ◽  
Daniel Nagaj ◽  
Jens Eisert
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Figure Of Merit ◽  
Nearest Neighbor ◽  
Many Body ◽  
Exponential Increase ◽  
Sign Problem ◽  
Simple Basis ◽  
Np Complete ◽  
Many Body Systems

Quantum Monte Carlo (QMC) methods are the gold standard for studying equilibrium properties of quantum many-body systems. However, in many interesting situations, QMC methods are faced with a sign problem, causing the severe limitation of an exponential increase in the runtime of the QMC algorithm. In this work, we develop a systematic, generally applicable, and practically feasible methodology for easing the sign problem by efficiently computable basis changes and use it to rigorously assess the sign problem. Our framework introduces measures of non-stoquasticity that—as we demonstrate analytically and numerically—at the same time provide a practically relevant and efficiently computable figure of merit for the severity of the sign problem. Complementing this pragmatic mindset, we prove that easing the sign problem in terms of those measures is generally an NP-complete task for nearest-neighbor Hamiltonians and simple basis choices by a reduction to the MAXCUT-problem.

scholarly journals Thermal and Quantum Fluctuation Effects in Quasiperiodic Systems in External Potentials

2019 ◽  
Vol 4 (4) ◽  
pp. 93
Author(s):  
Fabio Cinti ◽  
Tommaso Macrì
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Quantum Fluctuation ◽  
Pair Potential ◽  
Many Body ◽  
Harmonic Confinement ◽  
Intrinsic Length ◽  
Fluctuation Effects ◽  
The Many ◽  
Quantum Monte Carlo Methods

We analyze the many-body phases of an ensemble of particles interacting via a Lifshitz–Petrich–Gaussian pair potential in a harmonic confinement. We focus on specific parameter regimes where we expect decagonal quasiperiodic cluster arrangements. Performing classical Monte Carlo as well as path integral quantum Monte Carlo methods, we numerically simulate systems of a few thousand particles including thermal and quantum fluctuations. Our findings indicate that the competition between the intrinsic length scale of the harmonic oscillator and the wavelengths associated to the minima of the pair potential generically lead to a destruction of the quasicrystalline pattern. Extensions of this work are also discussed.

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