Matlab Programs developed by Li and his colleagues
Matlab Programs for plotting Generalized Numerical Ranges (by C.K. Li)
Product of two positive contractions
C.K. Li, D.C. Pelejo, and K.Z. Wang, Product of two positive constractions.

Twoposcon.m (by Diane Pelejo)
This program check whether a square matrix is the product of two positive contractions.
One needs to apply a unitary similarity to the matrix A to put it in a certain form to use the program.
Details are in the program file.
Decomposition of quantum gates
C.K. Li and D.C. Pelejo,
Decomposition of quantum gates, Int. J. Quantum Inform. 12, 1450002 (2014)

decomposition.m (by Diane Pelejo)
The program uses the recurrence decomposition scheme in the paper at
http://arxiv.org/abs/1311.3599 to
reduce a quantum gate (unitary matrix) into the product of simple
quantum gates with few controls.
It will display the
order of entries to be annihilated, the
(c_n...c_1)gate used and the single qubit gate V
used for the controlled gates.
One use the command:
[U,A,x,y,controls,num,V]=decomposition(n);
in the command line, where
n is the number of qubits and the
program will prompt for the user
to either choose to create a random unitary matrix or input the unitary matrix manually.
The variable U is the unitary matrix being decomposed,
the variable A is an
array of strings that describe the form of the gate, and (x,y) are the row and
column indices arranged according to their order of annihilation. The variable
controls gives the total number of controls used and num
is the number of
nontrivial unitary controlled gates used. The variable V is the product of the
controlled gates and hence, must always equal to the identity matrix.
This is used to help the user check that the decomposition is correct.

gatecount.m (by Diane Pelejo)
This program counts
the total number of controls in our scheme and that in the paper of
Vartiainen et al. at http://arxiv.org/abs/quantph/0312218.

pud.m (by Rebecca Roberts)
This is a Matlab program for decomposing an nbyn unitary matrix U
as the product of N = n(n1)/2 twolevel matrices
according to the permutation
P = [i_1, ..., i_n] of [1, ..., n].
The Matlab command: A = pud(U,P)
will generate the twolevel matrices A{1}, ..., A{N}, whose
product equal U.
One also needs the auxiliary Matlab program:
genDeletePos.m to do the decomposition.
Central Groupoids and Centeral Digraphs
F. Curtis, J. Drew, C.K. Li and D. Pragel,
Central groupoids, central digraphs, and zeroone matrices
A satisfying A^2 = J,
Central Groupoids, Central Digraphs, and ZeroOne Matrices $A$ Satisfying $A^2 = J$,
J. Combinatorial Theory, Series A, 105 (2004), 3550.
pdf file.
F. Curtis and D. Pragel,
Central groupoids, central digraphs, and zeroone matrices
A satisfying A^2 = J, REU report, College of William and Mary, 2002.
pdf file.
F. Curtis, J. Drew, C.K. Li and D. Pragel,
Computer Programs and Examples in the study of Central groupoids, central
digraphs, and zeroone matrices
A satisfying A^2 = J.
pdf file.

MakeStandard(k) :
creating the adjancy matrix of the standard central digraph.

MakeSwitch(p,q;r,s,A) :
performing the switch [p,q;r,s] on the adjancency matrix
A of a central digraph.

AllRanks(k) :
creating adjacency matrices of central digraphs of all
possible ranks.

DRM(A) : applying a permutation similarity to
A to get a matrix with decreasing row multiplicity.

PerSim(A,B) : identifying
adjacency matrices that correspond to the same central
digraphs.