# This code is part of Qiskit.
#
# (C) Copyright IBM 2021.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""
T1 Experiment class.
"""
from typing import List, Optional, Union, Sequence
import numpy as np
from qiskit.circuit import QuantumCircuit
from qiskit.providers.backend import Backend
from qiskit_experiments.framework import BackendTiming, BaseExperiment, Options
from qiskit_experiments.library.characterization.analysis.t1_analysis import T1Analysis
[docs]
class T1(BaseExperiment):
r"""An experiment to measure the qubit relaxation time.
# section: overview
This experiment estimates the :math:`T_1` relaxation time of the qubit by
generating a series of circuits that excite the qubit then wait for different
intervals before measurement. The resulting data of excited population versus
wait time is fitted to an exponential curve to obtain an estimate for
:math:`T_1`.
# section: analysis_ref
:class:`.T1Analysis`
# section: manual
:doc:`/manuals/characterization/t1`
"""
@classmethod
def _default_experiment_options(cls) -> Options:
"""Default experiment options.
Experiment Options:
delays (Iterable[float]): Delay times of the experiments in seconds.
"""
options = super()._default_experiment_options()
options.delays = None
return options
def __init__(
self,
physical_qubits: Sequence[int],
delays: Union[List[float], np.array],
backend: Optional[Backend] = None,
):
"""
Initialize the T1 experiment class.
Args:
physical_qubits: a single-element sequence containing the qubit whose T1 is to be
estimated.
delays: Delay times of the experiments in seconds.
backend: Optional, the backend to run the experiment on.
Raises:
ValueError: If the number of delays is smaller than 3
"""
# Initialize base experiment
super().__init__(physical_qubits, analysis=T1Analysis(), backend=backend)
# Set experiment options
self.set_experiment_options(delays=delays)
[docs]
def circuits(self) -> List[QuantumCircuit]:
"""
Return a list of experiment circuits
Returns:
The experiment circuits
"""
timing = BackendTiming(self.backend)
circuits = []
for delay in self.experiment_options.delays:
circ = QuantumCircuit(1, 1)
circ.x(0)
circ.barrier(0)
circ.delay(timing.round_delay(time=delay), 0, timing.delay_unit)
circ.barrier(0)
circ.measure(0, 0)
circ.metadata = {"xval": timing.delay_time(time=delay)}
circuits.append(circ)
return circuits
def _metadata(self):
metadata = super()._metadata()
# Store measurement level and meas return if they have been
# set for the experiment
for run_opt in ["meas_level", "meas_return"]:
if hasattr(self.run_options, run_opt):
metadata[run_opt] = getattr(self.run_options, run_opt)
return metadata