Tools /
## MpExpectationOldThis tool calculates the expectation value of an operator. Computational complexity: {$L m^3 d^2 M^2$} [*] Matrix Product Toolkit version HEAD-0.7.4.0 (subversion tree rev 838M) Compiled on Feb 8 2008 at 18:56:58 usage: mp-expectation [options] <psi1> <operator> [<psi2>] Allowed options: --help show this help message -r [ --r ] display only the real part of the result -i [ --i ] display only the imaginary part of the result --notempfile don't use a temporary data file, keep everything in RAM (faster, but needs enough RAM) -v [ --verbose ] extra debug output The operator is of the form Only operators that transform as a scalar can have their expectation value taken, which therefore implies that the wavefunctions By default, the result is shown in C++ complex number format "(real,imag)". The There is a variant of ## Examplesmp-expectation groundstate lattice:H mp-expectation psi1 "lattice:N(2)" psi2 As usual, we use quotes (" or ') to stop the shell from interpreting the brackets. ## See also[*] in principle, the {$d^2M^2$} can be reduced to {$dM$}, with a re-summing of loop indices. But for typical operators this won't do much, the {$d^2M^2$} is the number of non-zero matrix elements, and in practice operators are usually quite sparse. |

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