qaqmc-c

template library implementation for Quasi-Adiabatic Quantum Monte Carlo.

Its implemented for a Nearest Neighbor TFIM based on references:

1. A. W. Sandvik PHYSICAL REVIEW E 68, 056701 (2003)
2. C.-W. Liu, A. Polkovnikov, A. W. Sandvik PHYSICAL REVIEW B 87, 174302 (2013)

it implements the 'two-way' evolution.

Template parameters:

• int L: linear system size
• int d: dimension of lattice
• int M: length of operator string
• int Nm: Nm <= 2*M+1 number of measurements points during evolution (Nm>0 includes assymetric expectation values).
• int mstep: number of Monte Carlo sweeps per Monte Carlo step.

Instantiation:

qaqmc<L,d,M,Nm,mstep> qmc(S_i,S_f,bc,output_file);

• double S_i: initial 'S' parameter for QA-QMC evolution
• double S_f: final 'S' parameter for QA-QMC evolution
• std::string bc: boundary conditions for operator string, must be one of the following:
  • "pzpz" polarized along the positive z-axis on both sides
  • "pxpx" polarized along the positive x-axis on both sides
  • "tr" tperiodic SSE trace boundary conditions.
• std::string output_file: string which constains the output file, which the data should be written to.

public methods of qaqmc:

• void write_out(void): write the current measurement results to the output file.
• void write_out_lock(void): writes the current measurement results to output file. the function creates a temporary file which is used to prevent other jobs from writting to thw same file simultaineiously.
• void EQstep(void): Perform Monte Carlo step without measurements, typically used when equilibrating simulation.
• void MCstep(void): Perform Monte Carlo step with measurements, after the completion of this function one should call either write_out() or write_out_lock().