State abstract type

State is the base abstract type which must be subtyped for the elements that span an hilbert space (or a Matrix space), and which also correspond to a configuration of the visible layer of the neural network.

Defining a new State concrete struct

It is possible that one wants to define a new type of state, which spans the density matrix space in a different way and gives a correspondence between visible layer configurations and elements in the density matrix in a novel way. To do so, one must take care of defining the following ingredients: - The mutable struct holding the state itself; - Accessor methods that can be used by the sampler and the problem to compute observables; - Methods for modyfing the state; - (optionally) constructors.

a State derivating from DualValuedState must define the following:

mutable struct ExampleState <: DualValuedState
	...
	...
end

Constructors

No default constructor must be created by itself, because it will be called from specific code of every NeuralNetwork. Though, the standard interface would require to define

ExampleState{...}({number params}, {Ints })

where number params are all parameters listing the length of the various items in the ExampleState, and {Ints} are the ints that initialize them.

Accessors

To define a new state, all those accessors must be defined:

• spacedimension(state::ExampleState) returning the size of the space where this state lives. For example, for N spins this will be 2^N
• half_space_dimension(state::ExampleState) returns the size of the physical hilbert space where the density matrix is defined. Usually 2^(N/2)
• toint(state::ExampleState) returning the state expressed as an integer
• nsites(state::ExampleState) returns the number of sites where this state is defined.
• vectorindex(state::ExampleState) ????
• neurontype(state::ExampleState) returning the type of the neuron for this state
• neurontype(::Type{ExampleState}) returning the type of the neuron for this state.

Operations

• flipat!(state, i::Integer)
• set!(state, i::Integer)
• add!(State, i::Integer)
• `setzero!(state)