# human2opspec.m

Converts user-friendly descriptions of spin states and operators into the formal operator and state description used by Spinach kernel.

## Syntax

The function supports three types of syntax:

1. If both inputs are strings, e.g.

      [opspecs,coeffs]=human2opspec(spin_system,'Lz','13C')


the function returns a list of single-spin opspecs for all spins with the specified name. In the example above, the list of Lz operator specifications for all 13C nuclei in the system would be returned. Valid labels for operators in this type of call are 'E', 'Lz', 'L+', 'L-' and 'Tl,m'. In the latter case, l and m are integers. Valid labels for the spins are standard isotope names as well as 'electrons', 'nuclei', 'all'.

2. If one input is a string and the other is a vector, e.g.

      [opspecs,coeffs]=human2opspec(spin_system,'Lz',[1 2 4])


the function returns a list of single-spin opspecs for all spins with the specified number. In the example above, the list of Lz operator specifications for all 13C nuclei in the system would be returned. Valid labels for operators in this type of call are 'E', 'Lz', 'L+', 'L-' and 'Tl,m'. In the latter case, l and m are integers.

3. If the two inputs are a cell array of strings and a cell array of numbers respectively, a product operator specification is produced, e.g.

      [opspecs,coeffs]=human2opspec(spin_system,{'Lz','L+'},{1,2})


would return the Lz(x)L+ product operator specification with Lz on spin 1 and L+ on spin 2. Valid labels for operators in the cell array are 'E', 'Lz', 'L+', 'L-' and 'Tl,m'. In the latter case, l and m are integers.

## Outputs

   opspecs    - Spinach operator specification: a cell array of
row vectors specifying which operator enters the
Kronecker product for which spin.

coeffs     - coefficient with which each of the Kronecker pro-
ducts enters the overall sum.


## Notes

Direct calls to this function should not be necessary, use operator.m and state.m functions instead.