Returns reference to single qubit in register.

Returns a sub-register, which begins at given offset and has given width.

Right after creation, register is independent and its OffsetToRoot equals 0. But after operations on many registers, included this, Register could be entangled with others and is no longer independent. The group of entangled registers has its RootRegister. Each register in such group is de facto a part of the Root. OffsetToRoot describes offset (from Least Significant Bit, which offset is 0) of the part in RootRegister.

The number of qubits contained in Register.