QuantumReservoirPy

Using quantum circuits as reservoirs in reservoir computing is fairly new. The current examples in the literature rely heavily on quantum circuits of a very periodic nature. This package is meant to simplify the creation and simulation of such periodic circuits.

See the documentation for this package.

Installation

QuantumReservoirPy is available as a pip-installable package on PyPI.

pip install quantumreservoirpy

This will install QuantumReservoirPy along with its dependent packages.

Alternative Options

Alternatively, you may clone the repository from GitHub

git clone https://github.com/OpenQuantumComputing/quantumreservoirpy.git

navigate to the repository

cd quantumreservoirpy

and install it from here.

pip install .

This is functionally equivalent to installing from PyPI.

Interface

The interface of this package is somewhat inspired by ReservoirPy. Consider checking out their tutorials to better understand this package.

A reservoir is in this package defined as a class implementing the abstract class QReservoir. To create a completely custom reservoir, you need to implement 5 functions as shown.

class CustomRes(QReservoir):
    def before(self, circuit):
        pass
    def during(self, circuit, timestep):
        pass
    def after(self, circuit):
        pass

    def run(self, timeseries, **kwargs):
        pass
    def predict(self, num_pred, model, from_series, **kwargs):
        pass

QuantumReservoirPy has some partially implemented reservoirs already, which have easier interfaces.

Static and Incremental

These reservoirs have implemented the run and predict methods, so you only need to implement before, during, and after.

All the reservoirs created with Static and Ìncremental have the same three layered circuit structure; they begin with an initialization, which is defined by before. Then, a small circuit is created for every timestep in the timeseries, which is defined by during. The third and last layer is defined by after.

from quantumreservoirpy.reservoirs import Static
class CustomRes(Static):
    def before(self, circuit):
        circuit.h(circuit.qubits)
        circuit.barrier()

    def during(self, circuit, timestep):
        circuit.initialize(str(timestep), [0])
        circuit.h(0)
        circuit.cx(0, 1)

    def after(self, circuit):
        circuit.barrier()
        circuit.measure_all()

res = CustomRes(n_qubits=2)
res.circuit([0, 1]).draw('mpl')

The three functions before, during, and after do the same thing for both Static and Incremental reservoirs. The difference between them is what happens when the reservoirs are run.

Running a Reservoir

Having created a reservoir, you can simply call reservoir.run.

states = res.run(timeseries)

This will return a np.ndarray of the same length as the timeseries, corresponding to the reservoir state at each timestep.

Static reservoirs run once and all measurements are reshaped to a (len(timeseries), -1) shape.

Incremental reservoirs run incrementally. For every state, only the last M steps of the timeseries is built at a time (M being a parameter of Incremental.__init__).

About

You can find out more about QuantumReservoirPy and contact the authors here.

This project is supported by SINTEF Digital.

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