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MpExpectation

The mp-expectation command calculates the expectation value of an operator with finite support. The wavefunction can be finite, infinite, or infinite-boundary.

Synopsis

mp-expectation [options] <psi> <operator> [psi2]

calculates {$\bigbraket{\mbox{psi}}{\mbox{operator}}{\mbox{psi2}}$}

The operator must be defined over a finite range of lattice sites, it is not possible to use mp-iexpectation to evaluate TriangularMPO's or ProductMPO's as these have infinite support. For infinite wavefunctions, it is not possible to calculate mixed expectation values where psi2 is different to psi1.

Options

--help

-r, --real

-i, --imag

If none of --real or --imag is specified, the default is to show both the real and imaginary parts.

Examples

1. local magnetization at site 5
   
   mp-expectation psi lat:"Sz(5)"
2. correlations of an SU(2) spin chain
   
   mp-expectation psi lat:"inner(S(0),S(1))"

See also

• To calculate expectation values of TriangularMPO's, see MpIMoments
• To calculate expectation values of ProductMPO's, see MpIOverlap