See also

A Jupyter notebook version of this tutorial can be downloaded here.

[1]:

from __future__ import annotations

from pathlib import Path

import numpy as np
import rich  # noqa:F401
from qcodes.parameters import ManualParameter

import quantify_core.data.handling as dh
from quantify_core.analysis.single_qubit_timedomain import T1Analysis
from quantify_core.data.handling import load_dataset
from quantify_scheduler import QuantumDevice, Schedule, ScheduleGettable
from quantify_scheduler.operations import Measure, Reset, X

from utils import display_dict, initialize_hardware, run_schedule, show_connectivity  # noqa:F401

[2]:

hw_config_path = "configs/tuning_transmon_coupled_pair_hardware_config.json"
device_path = "devices/transmon_device_2q.json"

[3]:

# Enter your own dataset directory here!
dh.set_datadir(dh.default_datadir())

Data will be saved in:
/root/quantify-data

[4]:

quantum_device = QuantumDevice.from_json_file(device_path)
qubit = quantum_device.get_element("q0")
quantum_device.hardware_config.load_from_json_file(hw_config_path)
cluster_ip = None
meas_ctrl, inst_coord, cluster = initialize_hardware(quantum_device, ip=cluster_ip)

T1#

Here we measure the \(T_1\) decoherence time of the qubit.

Setup#

In this section we configure the hardware configuration which specifies the connectivity of our system.

The experiments of this tutorial are meant to be executed with a Qblox Cluster controlling a transmon system. The experiments can also be executed using a dummy Qblox device that is created via an instance of the Cluster class, and is initialized with a dummy configuration. When using a dummy device, the analysis will not work because the experiments will return np.nan values.

Configuration file#

This is a template hardware configuration file for a 2-qubit system with a flux-control line which can be used to tune the qubit frequency. We will only work with qubit 0.

The hardware connectivity is as follows, by cluster slot:

QCM (Slot 2)
- \(\text{O}^{1}\): Flux line for q0.
- \(\text{O}^{2}\): Flux line for q1.
QCM-RF (Slot 6)
- \(\text{O}^{1}\): Drive line for q0 using fixed 80 MHz IF.
- \(\text{O}^{2}\): Drive line for q1 using fixed 80 MHz IF.
QRM-RF (Slot 8)
- \(\text{O}^{1}\) and \(\text{I}^{1}\): Shared readout line for q0/q1 using a fixed LO set at 7.5 GHz.

Note that in the hardware configuration below the mixers are uncorrected, but for high fidelity experiments this should also be done for all the modules.

Quantum device settings#

Here we initialize our QuantumDevice and our qubit parameters, checkout this tutorial for further details.

In short, a QuantumDevice contains device elements where we save our found parameters. Here we are loading a template for 2 qubits, but we will only use qubit 0.

T1#

[5]:

# This schedule can also be imported from quantify_scheduler.schedules.


def t1_sched(
    times: np.ndarray | float,
    qubit: str,
    repetitions: int = 1,
) -> Schedule:
    """
    Generate a schedule for performing a :math:`T_1` experiment.

    This measures the qubit relaxation time.

    Schedule sequence
        .. centered:: Reset -- pi -- Idle(tau) -- Measure

    See section III.B.2. of :cite:t:`krantz_quantum_2019` for an explanation of the Bloch-Redfield
    model of decoherence and the :math:`T_1` experiment.

    Parameters
    ----------
    times
        an array of wait times tau between the start of pi-pulse and the measurement.
    qubit
        the name of the device element e.g., :code:`"q0"` to perform the T1 experiment on.
    repetitions
        The amount of times the Schedule will be repeated.

    Returns
    -------
    :
        An experiment schedule.

    """
    device_element = qubit
    # ensure times is an iterable when passing floats.
    times = np.asarray(times)
    times = times.reshape(times.shape or (1,))

    schedule = Schedule("T1", repetitions)
    for i, tau in enumerate(times):
        schedule.add(Reset(device_element), label=f"Reset {i}")
        schedule.add(X(device_element), label=f"pi {i}")
        schedule.add(
            Measure(device_element, acq_index=i),
            ref_pt="start",
            rel_time=tau,
            label=f"Measurement {i}",
        )
    return schedule

[6]:

tau = ManualParameter(name="tau_delay", unit="s", label="Delay")
tau.batched = True

t1_sched_kwargs = {"qubit": qubit.name, "times": tau}

gettable = ScheduleGettable(
    quantum_device,
    schedule_function=t1_sched,
    schedule_kwargs=t1_sched_kwargs,
    real_imag=False,
    batched=True,
)
meas_ctrl.gettables(gettable)

[7]:

delay_setpoints = np.arange(40e-9, 200e-6, 500e-9)

meas_ctrl.settables(tau)
meas_ctrl.setpoints(delay_setpoints)

quantum_device.cfg_sched_repetitions(300)
t1_ds = meas_ctrl.run("T1 experiment")
t1_ds

Starting batched measurement...
Iterative settable(s) [outer loop(s)]:
         --- (None) ---
Batched settable(s):
         tau_delay
Batch size limit: 400

[8]:

if cluster_ip is None:
    notebook_dir = Path.cwd()
    dh.set_datadir(notebook_dir / "data")
    t1_ds = load_dataset("20250205-203226-565-47a4c6")
t1_analysis = T1Analysis(dataset=t1_ds)
t1_analysis.run().display_figs_mpl()

../../../_images/applications_quantify_transmon_t1_13_0.png

[9]:

inst_coord.last_schedule.compiled_instructions

[10]:

display_dict(quantum_device.hardware_config())

[10]:

[11]:

quantum_device.to_json_file("devices/")

[11]:

'devices/device_2q_2025-03-12_18-04-19_UTC.json'

T1#

Setup#

Configuration file#

Quantum device settings#

T1#

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