Dynamical Decoupling with FiQCI EMS

Dynamical Decoupling with FiQCI EMS#

What is Dynamical Decoupling:#

Dynamical decoupling (DD) is a quantum error suppression technique that reduces the effects of decoherence on idle qubits. When a qubit is idle during a quantum circuit, e.g. while other qubits are being operated on, it is exposed to unwanted interactions with its environment. These interactions cause the qubit’s state to decay over time, introducing errors into the computation.

DD works by inserting sequences of fast control pulses (such as X and Y gates) on idle qubits. These pulses effectively refocus the qubit’s evolution, averaging out the environmental noise over time. The key idea is that if noise acts slowly compared to the rate of the applied pulses, the net effect of the noise is suppressed.

Common DD sequences include:

  • XY: Alternating X and Y gates. A simple and widely used sequence that protects against both bit-flip and phase-flip noise.

  • XYXY: A repeated XY sequence offering stronger suppression for longer idle periods.

  • Custom PRX sequences: User-defined rotation sequences for advanced noise profiles.

Usage#

Dynamical decoupling is enabled by default at mitigation_level=2 or it can be enabled with the primitives dd() method.

For more detailed usage see FiQCISampler or FiQCIEstimator

Combining DD with other compilation options#

DD is submitted through IQM’s CircuitCompilationOptions, which is also how you reach settings EMS does not wrap (heralding, MOVE gate validation, MOVE gate frame tracking). Passing your own options to run() keeps every non-DD field and only sets the DD ones, so the two compose:

from iqm.iqm_client import CircuitCompilationOptions, MoveGateValidationMode

sampler = FiQCISampler(backend, mitigation_level=2)  # DD on
sampler.run(
    circuit,
    shots=4096,
    circuit_compilation_options=CircuitCompilationOptions(
        move_gate_validation=MoveGateValidationMode.ALLOW_PRX
    ),
)

The DD strategy from dd() (or the mitigation level) wins over a dd_mode/dd_strategy set in your own options, and you get a warning if both are configured. To submit with your own DD strategy instead, turn EMS’s off with dd(enabled=False).

References#