Experimental API

In this page we present some experimental interfaces of NetKet. Those are not guaranteed to be API-stable, and might change without notice (other than the changelog) among minor releases. The netket.experimental module mirrors the standard netket module structure, and we suggest to use it as follows:

import netket as nk
import netket.experimental as nkx

Quantum State Reconstruction

The Quantum State Reconstruction algorithm performs an approximate tomographic reconstruction of measurement data coming from a quantum computer (or similar device) using a Pure or Mixed quantum state.

QSR	Quantum state reconstruction driver minimizing KL divergence.

Samplers

This module contains the Metropolis Parallel Tempered sampler. This sampler is experimental because we believe it to be correct, but our tests fail. We believe it to be a false negative: possibly the implementation of the sampler is correct, but the test is too tight. Until we will have verified this hypothesis and updated the tests in order not to fail, we provide the current implementation as-is, in the hope that some contributor might take up that work.

The other experimental sampler is MetropolisSamplerPmap, which makes use of jax.pmap() to use different GPUs/CPUs without having to use MPI. It should scale much better over several CPUs, but you have to start jax with a specific environment variable.

sampler.MetropolisPtSampler	Metropolis-Hastings with Parallel Tempering sampler.
sampler.MetropolisLocalPt	Sampler acting on one local degree of freedom.
sampler.MetropolisExchangePt	This sampler acts locally only on two local degree of freedom \(s_i\) and \(s_j\), and proposes a new state: \(s_1 \dots s^\prime_i \dots s^\prime_j \dots s_N\), where in general \(s^\prime_i \neq s_i\) and \(s^\prime_j \neq s_j\).
sampler.MetropolisSamplerPmap	Metropolis-Hastings sampler for an Hilbert space according to a specific transition rule where chains are split among the available devices (jax.devices()).

Logging

This module contains experimental loggers that can be used with the optimization drivers.

logging.HDF5Log

HDF5 Logger, that can be passed with keyword argument logger to Monte Carlo drivers in order to serialize the output data of the simulation.

Variational State Interface

vqs.variables_from_file	Loads the variables of a variational state from a .mpack file.
vqs.variables_from_tar	Loads the variables of a variational state from the i-th element of a .tar archive.

Time Evolution Driver

Apple ARM (M1) processors

Those drivers are automatically jitted with jax.jit. To disable jitting set

netket.config.netket_disable_ode_jit = True

or set the equivalent environment variable.

TDVP	Variational time evolution based on the time-dependent variational principle which, when used with Monte Carlo sampling via netket.vqs.MCState, is the time-dependent VMC (t-VMC) method.
driver.TDVPSchmitt	Variational time evolution based on the time-dependent variational principle which, when used with Monte Carlo sampling via netket.vqs.MCState, is the time-dependent VMC (t-VMC) method.

ODE Integrators

This is a collection of ODE integrators that can be used with the TDVP driver above.

Apple ARM (M1) processors

Those drivers are automatically jitted with jax.jit. To disable jitting set

netket.config.netket_disable_ode_jit = True

or set the equivalent environment variable.

dynamics.Euler	The canonical first-order forward Euler method.
dynamics.Heun	The second order Heun's method.
dynamics.Midpoint	The second order midpoint method.
dynamics.RK12	The second order Heun's method.
dynamics.RK23	2nd order adaptive solver with 3rd order error control, using the Bogacki–Shampine coefficients
dynamics.RK4	The canonical Runge-Kutta Order 4 method.
dynamics.RK45	Dormand-Prince's 5/4 Runge-Kutta method.

Fermions

This modules contains hilbert space and operator implementations of fermions in second quantization. It is experimental until it has been thoroughly tested by the community, meaning feedback is welcome.

hilbert.SpinOrbitalFermions

Hilbert space for 2nd quantization fermions with spin s distributed among n_orbital orbitals.

operator.FermionOperator2nd	A fermionic operator in \(2^{nd}\) quantization.
operator.fermion.create	Builds the fermion creation operator \(\hat{a}^\dagger\) acting on the site-th of the Hilbert space hilbert.
operator.fermion.destroy	Builds the fermion destruction operator \(\hat{a}\) acting on the site-th of the Hilbert space hilbert.
operator.fermion.number	Builds the number operator \(\hat{a}^\dagger\hat{a}\) acting on the site-th of the Hilbert space hilbert.