qcmet.benchmarks.T2#

class qcmet.benchmarks.T2(qubit_index=0, method='hahn', num_idle_gates_per_circ=None, detuning_phase=None, delay=None, save_path=None)[source]#

Benchmark class for estimating the T2 coherence time of a qubit.

This benchmark supports two methods for measuring T2: - ‘ramsey’: Ramsey interference for measuring T2* (dephasing time) - ‘hahn’: Hahn echo (spin echo) for measuring T2 (coherence time)

The Ramsey method is sensitive to low-frequency noise and detuning, while the Hahn echo method refocuses static field inhomogeneities.

config#

Configuration dictionary containing: - method (str): Either ‘ramsey’ or ‘hahn’ - num_idle_gates_per_circ (array-like): Number of idle gates per circuit - detuning_phase (float): Phase accumulation per idle gate for Ramsey

(defaults: np.pi/100 for idle_gates and np.pi/10 for delay gates)

  • delay (array-like): Length of delay per circuit

Type:

dict

fit_result#

Stores the results of the fit.

Type:

dict

success#

Indicates whether the curve fitting was successful.

Type:

bool

__init__(qubit_index=0, method='hahn', num_idle_gates_per_circ=None, detuning_phase=None, delay=None, save_path=None)[source]#

Initialize the T2 benchmark.

Parameters:

  • qubit_index (int, optional) – The qubit index for routing. Defaults to 0.

  • method (str, optional) – Method to use for T2 measurement. Either ‘ramsey’ or ‘hahn’. Defaults to ‘hahn’.

  • num_idle_gates_per_circ (array-like, optional) – Sequence of idle gate counts to use. For Ramsey: defaults to np.arange(1, 1000, 50) For Hahn: defaults to np.arange(1, 2000, 100)

  • detuning_phase (float, optional) – Phase per idle/delay gate to simulate detuning in Ramsey.Defaults to np.pi/100 for idle gates approach and np.pi/10 for delay gates approach. These defaults had produced sensible fits for T2 and T2* with a noisy simulator.

  • delay (array-like, optional) – Sequence of delay gates to use in circuits. This is for alternate methodto the idle_gates approach. Do not set an argument for num_idle_gates_per_circ when defining delay. Units are in microseconds.

  • save_path (str | Path | FileManager | None, optional) – Directory path to save results. Defaults to None.

Raises:

  • ValueError – If method is not ‘ramsey’ or ‘hahn’.

  • ValueError – If num_idle_gates_per_circ and delay are both specified.

Methods

__init__([qubit_index, method, ...])

Initialize the T2 benchmark.

analyze()

Analyze measurements to return benchmark results.

generate_circuits()

Generate benchmark circuits, user facing.

hahn_fit_func(x, amp, dr, b)

Exponential decay function for Hahn echo.

has_plotting()

Check if _plot function is implemented in benchmark.

load_circuit_measurements(circuit_measurements)

Load measurement counts into the experiment_data DataFrame.

measurements_to_probabilities()

Convert raw measurement counts to normalized probabilities.

plot([axes])

Plot benchmark result, user facing.

ramsey_fit_func(x, amp, dr, f, phi, b)

Damped oscillation function for Ramsey interference.

run([device, num_shots, max_circs_per_job])

Run benchmark.

save()

Save benchmark current state.

set_save_path(save_path)

Set benchmark save path if not set in class constructor.

Attributes

circuits

Gets all benchmark circuits.

experiment_data

Getter for experiment_data dataframe.

num_qubits

Number of qubits in this benchmark.
static ramsey_fit_func(x, amp, dr, f, phi, b)[source]#

Damped oscillation function for Ramsey interference.

Models: amp * exp(-x/T2*) * cos(2πfx + φ) + b

Parameters:

  • x (float or array-like) – Independent variable (number of idle gates or delay).

  • amp (float) – Amplitude of oscillation.

  • dr (float) – Decay rate (T2* time).

  • f (float) – Oscillation frequency.

  • phi (float) – Phase offset.

  • b (float) – Baseline offset.

Returns:

Computed damped oscillation values.

Return type:

float or array-like

static hahn_fit_func(x, amp, dr, b)[source]#

Exponential decay function for Hahn echo.

Models: amp * exp(-x/T2) + b

Parameters:

  • x (float or array-like) – Independent variable (number of idle gates or delay).

  • amp (float) – Amplitude of the exponential decay.

  • dr (float) – Decay rate (T2 time).

  • b (float) – Baseline offset.

Returns:

Computed exponential decay values.

Return type:

float or array-like