Partial Trace and Invariant Integration
In the case of finite dimensional Hilbert spaces, there is a useful way of looking at partial trace involving integration with respect to a suitably normalized Haar measure μ over the unitary group U(W) of W. Suitably normalized means that μ is taken to be a measure with total mass dim(W).
Theorem. Suppose V, W are finite dimensional Hilbert spaces. Then
commutes with all operators of the form and hence is uniquely of the form . The operator R is the partial trace of T.
Read more about this topic: Partial Trace
Famous quotes containing the words partial, trace and/or integration:
“Both the man of science and the man of art live always at the edge of mystery, surrounded by it. Both, as a measure of their creation, have always had to do with the harmonization of what is new with what is familiar, with the balance between novelty and synthesis, with the struggle to make partial order in total chaos.... This cannot be an easy life.”
—J. Robert Oppenheimer (1904–1967)
“‘Tis chastity, my brother, chastity.
She that has that is clad in complete steel,
And like a quivered nymph with arrows keen
May trace huge forests and unharbored heaths,
Infamous hills and sandy perilous wilds,
Where, through the sacred rays of chastity,
No savage fierce, bandit, or mountaineer
Will dare to soil her virgin purity.”
—John Milton (1608–1674)
“The more specific idea of evolution now reached is—a change from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, accompanying the dissipation of motion and integration of matter.”
—Herbert Spencer (1820–1903)