mm.lab_dev.simulator.Simulator

class mrmustard.lab_dev.simulator.Simulator

Bases: object

A simulator for quantum circuits.

Circuits can be simulated by using the run method of Simulator:

>>> from mrmustard.lab_dev import *
>>> import numpy as np

>>> # initialize a circuit
>>> state = Number(modes=[0, 1], n=[2, 0], cutoffs=2)
>>> gate = BSgate([0, 1], theta=np.pi/4)
>>> proj1 = Number(modes=[1], n=[0]).dual
>>> circuit = Circuit([state, gate, proj1])

>>> # run the simulation
>>> result = Simulator().run(circuit)

>>> # the simulator returns a component that can be potentially be plugged
>>> # into another circuit
>>> assert isinstance(result, CircuitComponent)

The simulation is carried out by contracting the components of the given circuit in pairs, until only one component is left and returned. In the examples above, the contractions happen in a “left-to-right” fashion, meaning that the left-most component in the circuit (state) is contracted with the one in its right (gate), and finally the resulting component is contracted with the projector. This provides a simple and convenient way to run simulations, but for large circuits, different contraction paths may be more efficient.

The path attribute of Circuits allows customising the contraction order and potentially speeding up the simulation. When a path of the type [(i, j), (l, m), ...] is given, the simulator creates a dictionary of the type {0: c0, ..., N: cN}, where [c0, .., cN] is the circuit.component list. Then:

• The two components ci and cj in positions i and j are contracted. ci is replaced by the resulting component cj >> cj, while cj is popped.

• The two components cl and cm in positions l and m are contracted. cl is replaced by the resulting component cl >> cm, while cm is popped.

• Et cetera.

Below is an example where a circuit is simulated in a “right-to-left” fashion:

>>> from mrmustard.lab_dev import *
>>> import numpy as np

>>> state = Number(modes=[0, 1], n=[2, 0], cutoffs=2)
>>> gate = BSgate([0, 1], theta=np.pi/4)
>>> proj01 = Number(modes=[0, 1], n=[2, 0]).dual

>>> # initialize the circuit and specify a custom path
>>> circuit = Circuit([state, gate, proj01])
>>> circuit.path = [(1, 2), (0, 1)]

>>> result = Simulator().run(circuit)

The setter for path also validates the path using the validate_path function of Circuit.

Methods

run(circuit)

Runs the simulations of the given circuit.

run(circuit)

Runs the simulations of the given circuit.

Parameters:

circuit (Circuit) – The circuit to simulate.

Return type:

CircuitComponent

Returns:

A circuit component representing the entire circuit.

Raises:

ValueError – If circuit has an incomplete path.

code/api/mrmustard.lab_dev.simulator.Simulator

 

Download Python script

 

Download Notebook

 

View on GitHub