Matrix Product Toolkit | Tools / MpRandom

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mp-random is used to create a random matrix product state, as a superposition of a number of product states.

Synopsis

mp-random -l <lattice> -u <size> -o <filename> [options]

The mp-random tool constructs a random wavefunction as a superposition of product states.

Options

--help

show help message

-l, --lattice

Lattice file (required)

-u, --unitcell

Unit cell size (required)

-q, --quantumnumber

Target quantum number of the wavefunction (required, unless the lattice has no conserved symmetries)

-c, --count

The output wavefunction is a superposition of this many random product states (default 20)

-o, --out

Output filename (required)

-b, --beta

Inverse temperature for Monte Carlo simulated annealing (default 3)

-s, --seed

Random seed - with the same parameters and same seed, the output wafefunction is reproducible. By default the random seed is chosen from the system random number generator.

-i, --infinite

Construct an infinite wavefunction as output

-f, --force

Force overwriting the output file, if it exists

Examples

example 1
example 2

Notes

This program is typically used to generate a random state to use as input for the finite DMRG program. The iDMRG program uses the same algorithm to generate initial states if you use the --create option; indeed this is equivalent to constructing a random iMPS with mp-random --infinite.

If you specify a target quantum number that is not actually possible (ie. the dimension of the Fock space is zero, because there is no combination of local basis states that can give that quantum number), then mp-random will go into an infinite loop.

In some corner cases, the convergence of the algorithm can be slow. This is the case, for example, with a lattice that is nearly empty or nearly full. In this case, reducing the thermodynamic temperature for the montecarlo sampling may be beneficial (ie. increase the --beta parameter).