FiQCISampler

FiQCISampler#

FiQCISampler is a sampling interface that wraps an IQM backend and applies error mitigation to measurement results. It executes quantum circuits and returns mitigated counts.

Basic Configuration#

Initialize the sampler with an IQM backend, mitigation level, and optional parameters:

from fiqci.ems import FiQCISampler

# Initialize sampler with mitigation level 1
sampler = FiQCISampler(backend, mitigation_level=1, calibration_shots=2000, calibration_file="cals.json")

For more details see the API reference documentation for FiQCISampler.

Mitigation Levels#

Mitigation levels apply predefined sets of error mitigation techniques.

Level

Mitigation Applied

Technique

0

None

Raw results

1

Readout Error Mitigation

M3 (matrix-free measurement mitigation)

2

Level 1 + Dynamical Decoupling

Dynamical Decoupling standard sequence (see below)

3

Level 2 + Pauli Twirling

Pauli Twirling with 10 twirls on all two-qubit gates

Mitigation Options#

Mitigators can also be configured manually using the provided methods.

REM (Readout Error Mitigation)#

Readout error mitigation uses M3 (matrix-free measurement mitigation) to correct measurement errors. It is enabled by default at mitigation level 1.

Configure REM using the rem() method:

sampler.rem(enabled=True, calibration_shots=2000, calibration_file="cals.json")

Parameter

Default

Description

enabled

True

Enable or disable readout error mitigation

calibration_shots

1000

Number of shots used for M3 calibration circuits

calibration_file

None

Path to save/load calibration data (JSON). Reuses cached calibrations when available.

Dynamical Decoupling (DD)#

Dynamical decoupling inserts sequences of gates to mitigate decoherence. It is enabled at mitigation level 2.

Configure DD using the dd() method:

sampler.dd(enabled=True, gate_sequences=None) # None uses a standard set of sequences

The standard sequence is:

[
    (9, 'XYXYYXYX', 'asap'),
    (5, 'YXYX', 'asap'),
    (2, 'XX', 'center'),
]

Parameter

Default

Description

enabled

True

Enable or disable DD

gate_sequences

None
List of (threshold_length, sequence, strategy) tuples defining DD behavior. If None, uses a standard set of sequences.

  • threshold_length: Minimum idle period (threshold_length times duration of a single-qubit gate) to apply the sequence. If None, uses len(sequence) or 2 if sequence is None.

  • sequence: List of gate names or PRXSequence defining the DD sequence.

  • strategy: Strategy for applying the sequence. One of:

    • "asap": Apply the sequence as soon as possible whenever the idle period exceeds the threshold.

    • "alap": Apply the sequence _as late as possible_ whenever the idle period exceeds the threshold.

    • "center": Apply the sequence centered within idle periods exceeding the threshold.

Pauli Twirling#

Pauli twirling sandwiches two-qubit gates with random single-qubit Pauli gates to mitigate coherent errors. It is enabled at mitigation level 3.

Configure Pauli Twirling using the pauli_twirl() method:

sampler.pauli_twirl(enabled=True, num_twirls=10, gates_to_twirl=None) # None twirls all two-qubit gates

Inspecting Options#

Use the mitigator_options property to view currently applied mitigation settings:

sampler.mitigator_options

Examples#