# Theory

On this page, we present the fundamental theoretical models that underpin QTCAD.

In Section 1 to Section 9, we describe the mathematical models defining each solver in the device simulator, along with physical quantities that can be calculated using these solvers.

In Section 10 and Section 11, we consider the theoretical concepts that underlie the transport simulator.

Finally in Section 12, we describe the theory behind the qubit simulator.

- 1. Poisson solvers
- 2. Band alignment in heterostructures
- 3. Schrödinger solvers
- 4. Operators
- 5. Multivalley effective-mass theory solver
- 6. Lever arm theory
- 7. Schrödinger–Poisson solver
- 8. Many-body solver
- 9. Exchange interaction theory
- 10. Transport in the Coulomb blockade regime
- 11. The nonequilibrium Green’s function (NEGF) formalism
- 12. Quantum control
- 13. Bibliography