Uniqueness of the standard form of the generator of a quantum dynamical semigroup

I. Siemon, Alexander Semenovich Holevo, Reinhard F. Werner

Dynamical semigroups have become the key structure for describing open system dynamics in all of physics. Bounded generators are known to be of a standard form, due to Gorini, Kossakowski, Sudarshan and Lindblad. This form is often used also in the unbounded case, but rather little is known about the general form of unbounded generators. In this paper we first give a precise description of the standard form in the unbounded case, emphasizing intuition, and collecting and even proving the basic results around it. We also give a cautionary example showing that the standard form must not be read too naively. Further examples are given of semigroups, which appear to be probability preserving to first order, but are not for finite times. Based on these, we construct examples of generators which are not of standard form.

Göran Lindblad

Kalyanapuram Rangachari Parthasarathy

Using the tool of quantum characteristic functions of [Formula: see text]-mode states in the boson Fock space [Formula: see text] we construct a semigroup of quantum information channels. This leads to a special class of one-parameter semigroups of such channels. These semigroups are concrete but their generators have unbounded operator coefficients. These one-parameter semigroups are also quantum dynamical semigroups and the form of the generators involves additional features which do not appear in the standard Gorini-Kossakawski-Sudarshan-Lindbald (GKSL) form. A heuristic discussion of the form of these generators is included. In the wake of this analysis many open problems arise naturally.

Wawrzyniec Guz

Andrzej Posiewnik

Gianfausto Dell’Antonio

In Lecture “Lecture 10: Derivations and Generators. K.M.S. Condition. Elements of Modular Structure. Standard Form” we have discussed some aspects of quantum dynamics when it is represented by a one-parameter group of automorphisms of a $$C^*$$ -algebra.