On diagonal quantum channels

Diagonal-transition quantum cascade detector

On approximation of quantum channels

Although a major attention in quantum information theory so far was paid to finite-dimensional systems and channels, there is an increasing interest in infinite-dimensional generalizations (see [4], [8], [9], [15]-[18] and references therein). In the present paper we develop an approximation approach to infinite dimensional quantum channels based on detailed investigation of the continuity prop...

Off-diagonal quantum holonomy along density operators

Uhlmann’s concept of quantum holonomy for paths of density operators is generalised to the off-diagonal case providing insight into the geometry of state space when the Uhlmann holonomy is undefined. Comparison with previous off-diagonal geometric phase definitions is carried out and an example comprising the transport of a Bell-state mixture is given.

Rational Hadamard products via Quantum Diagonal Operators

We use the remark that, through Bargmann-Fock representation, diagonal operators of the Heisenberg-Weyl algebra are scalars for the Hadamard product to give some properties (like the stability of periodic fonctions) of the Hadamard product by a rational fraction. In particular, we provide through this way explicit formulas for the multiplication table of the Hadamard product in the algebra of r...

Quantum Channels in Quantum Gravity

The black hole final state proposal implements manifest unitarity in the process of black hole formation and evaporation in quantum gravity, by postulating a unique final state boundary condition at the singularity. We argue that this proposal can be embedded in the gauge/gravity context by invoking a path integral formalism inspired by the Schwinger-Keldysh like thermo-field double constructio...