Skip to content

Executing a quantum program

Let us revisit the quantum program described in the Quantum program page.

from qoolqit import PiecewiseLinear
from qoolqit import Register, Drive, QuantumProgram
from qoolqit import MockDevice

# Defining the Drive
wf0 = PiecewiseLinear([1.0, 2.0, 1.0], [0.0, 0.5, 0.5, 0.0])
wf1 = PiecewiseLinear([1.0, 2.0, 1.0], [-1.0, -1.0, 1.0, 1.0])
drive = Drive(amplitude = wf0, detuning = wf1)

# Defining the Register
coords = [(0.0, 0.0), (0.0, 1.0), (1.0, 0.0), (1.0, 1.0)]
register = Register.from_coordinates(coords)

# Creating the Program
program = QuantumProgram(register, drive)

# Compiling the Program
device = MockDevice()
program.compile_to(device)

The compiled program is ready to be executed using its run() method. The signature of this method is the following: 

def run(
    self,
    backend_name: BackendName = BackendName.QUTIP,
    result_type: ResultType = ResultType.STATEVECTOR,
    runs: int = 100,
    evaluation_times: list[float] = [1.0],
    **backend_params: Any,
) -> OutputType:
    ...

The execution process is primarily controlled by two arguments: backend_name and result_type.

The backend_name parameter expects a value from the BackendName enumeration, which specifies the computational backend responsible for simulating the underlying Pulser sequence. Supported values include QUTIP and EMUMPS, corresponding to the QuTiP backend for Pulser and the emu-mps quantum emulator, respectively.

The result_type argument determines the format of the output returned by the run() method. It accepts values from the ResultType enumeration: STATEVECTOR and BITSTRINGS.

  • STATEVECTOR returns a NumPy array of shape \(T \times 2^N\), representing the quantum state vectors of an \(N\)-qubit system at \(T\) time points.

  • BITSTRINGS returns a list of length \(T\), where each element is a Counter object containing the counts of the sampled bitstrings of the system’s output state at the corresponding time point. The total number of samples is given by the runs argument of the run() method.

The collection of \(T\) time points where the output states are returned are controlled by the evaluation_time argument. It accepts a list of floats between 0.0 and 1.0 that are mapped internally to the whole duration of the underlying sequence of the quantum program.

Finally, the user can pass keyword arguments for the backend's internal configuration. The corresponding documentation on the underlying configuration object is available here.

Let us run the quantum program defined previously and request the state vectors as output.

from qoolqit.execution import BackendName, ResultType
import numpy as np

# Define the evaluation times list
T = 101
evaluation_times = np.linspace(0, 1, T).tolist()

# Simulate with QUTIP backend and output state vectors
qutip_state_vecs = program.run(
    backend_name=BackendName.QUTIP,
    result_type=ResultType.STATEVECTOR,
    evaluationtimes=evaluation_times)

print("Shape of the output for state vectors:")
print(qutip_state_vecs.shape)

print("Final state vector:")
print(qutip_state_vecs[-1])

Shape of the output for state vectors:
(1, 16)
Final state vector:
[ 0.32824231-0.04375191j  0.29735705-0.05562653j  0.29735705-0.05562653j
 -0.11008115-0.21027933j  0.29735705-0.05562653j -0.11008115-0.21027933j
  0.23702074-0.22449441j -0.09603816+0.10719559j  0.29735705-0.05562653j
  0.23702074-0.22449441j -0.11008115-0.21027933j -0.09603816+0.10719559j
 -0.11008115-0.21027933j -0.09603816+0.10719559j -0.09603816+0.10719559j
  0.04086465-0.03547378j]

We can run similar simulation and output bitstrings instead.

# Number of samples
runs = 1000

# Simulate with EMUMPS backend and output bitstring counts
emumps_bitstrings = program.run(
    backend_name=BackendName.EMUMPS,
    result_type=ResultType.BITSTRINGS,
    evaluation_times=evaluation_times,
    runs=runs)

print("Length of the output list:")
print(len(emumps_bitstrings))

print("Final state bitstrings:")
print(emumps_bitstrings[-1])

Length of the output list:
100
Final state bitstrings:
Counter({'1001': 124, '0000': 103, '0110': 98, '0100': 96, '1000': 95, '0001': 93, '0010': 87, '0011': 59, '0101': 58, '1010': 51, '1100': 50, '1110': 25, '1101': 25, '0111': 17, '1011': 17, '1111': 2})