netket.hilbert.Fock#
- class netket.hilbert.Fock[source]#
Bases:
HomogeneousHilbert
Hilbert space obtained as tensor product of local fock basis.
- Inheritance
- __init__(n_max=None, N=1, n_particles=None, constraint=None)[source]#
Constructs a new
Boson
given a maximum occupation number, number of sites and total number of bosons.- Parameters:
n_max (
int
|None
) – Maximum occupation for a site (inclusive). If None, the local occupation number is unbounded.N (
int
) – number of bosonic modes (default = 1)n_particles (
int
|None
) – Constraint for the number of particles. If None, no constraint is imposed.constraint (
DiscreteHilbertConstraint
|None
) – A custom constraint on the allowed configurations. This argument cannot be specified at the same time asn_particles
. The constraint must be a subclass ofDiscreteHilbertConstraint
Examples
Simple boson hilbert space.
>>> from netket.hilbert import Fock >>> hi = Fock(n_max=5, n_particles=11, N=3) >>> print(hi.size) 3 >>> print(hi.n_states) 15
- Attributes
- constrained#
The hilbert space does not contain prod(hilbert.shape) basis states.
Typical constraints are population constraints (such as fixed number of bosons, fixed magnetization…) which ensure that only a subset of the total unconstrained space is populated.
Typically, objects defined in the constrained space cannot be converted to QuTiP or other formats.
- constraint#
The constraint inflicted upon this poor Hilbert space.
Instead of all possible combinations of local states, only those satisfying the constraint are part of this Hilbert space.
- is_finite#
Whether the local hilbert space is finite.
- is_indexable#
Whether the space can be indexed with an integer
- local_size#
Size of the local degrees of freedom that make the total hilbert space.
- local_states#
A list of discrete local quantum numbers. If the local states are infinitely many, None is returned.
- n_max#
The maximum number of bosons per site, or None if the number is unconstrained.
- n_particles#
The total number of particles, or None if the number is unconstrained.
- n_states#
The total dimension of the many-body Hilbert space. Throws an exception iff the space is not indexable.
- shape#
The size of the hilbert space on every site.
- size#
The total number number of degrees of freedom.
- Methods
- all_states()[source]#
Returns all valid states of the Hilbert space.
Throws an exception if the space is not indexable.
- Return type:
- Returns:
A (n_states x size) batch of states. this corresponds to the pre-allocated array if it was passed.
- local_indices_to_states(x, dtype=None)[source]#
Converts a tensor of integers to the corresponding local_values in this hilbert space.
Equivalent to
The input last dimension must match the size of this Hilbert space. This function can be jax-jitted.
- numbers_to_states(numbers)[source]#
Returns the quantum numbers corresponding to the n-th basis state for input n.
n is an array of integer indices such that
numbers[k]=Index(states[k])
. Throws an exception iff the space is not indexable.This function validates the inputs by checking that the numbers provided are smaller than the Hilbert space size, and throws an error if that condition is not met. When called from within a jax.jit context, this uses {func}`equinox.error_if` to throw runtime errors.
- Parameters:
numbers (
numpy.array
) – Batch of input numbers to be converted into arrays of quantum numbers.- Return type:
- ptrace(sites)[source]#
Returns the hilbert space without the selected sites.
Not all hilbert spaces support this operation.
- random_state(key=None, size=None, dtype=<class 'numpy.float32'>)[source]#
Generates either a single or a batch of uniformly distributed random states. Runs as
random_state(self, key, size=None, dtype=np.float32)
by default.- Parameters:
key – rng state from a jax-style functional generator.
size (
int
|None
) – If provided, returns a batch of configurations of the form(size, N)
if size is an integer or(*size, N)
if it is a tuple and where \(N\) is the Hilbert space size. By default, a single random configuration with shape(#,)
is returned.dtype – DType of the resulting vector.
- Return type:
- Returns:
A state or batch of states sampled from the uniform distribution on the hilbert space.
Example
>>> import netket, jax >>> hi = netket.hilbert.Qubit(N=2) >>> k1, k2 = jax.random.split(jax.random.PRNGKey(1)) >>> print(hi.random_state(key=k1)) [1. 0.] >>> print(hi.random_state(key=k2, size=2)) [[0. 0.] [0. 1.]]
- states()[source]#
Returns an iterator over all valid configurations of the Hilbert space. Throws an exception iff the space is not indexable. Iterating over all states with this method is typically inefficient, and
`all_states`
should be preferred.
- states_at_index(i)[source]#
A list of discrete local quantum numbers at the site i.
If the local states are infinitely many, None is returned.
- Parameters:
i (
int
) – The index of the desired site.- Returns:
A list of values or None if there are infinitely many.
- states_to_local_indices(x)[source]#
Returns a tensor with the same shape of x, where all local values are converted to indices in the range 0…self.shape[i]. This function is guaranteed to be jax-jittable.
For the Fock space this returns x, but for other hilbert spaces such as Spin this returns an array of indices.
Warning
This function is experimental. Use at your own risk.