Add dynamical decoupling as an optional error mitigation tool

[Changhao-Li]

Motivation

Dynamical decoupling (DD) is a quantum control technique that can suppress the decoherence of the system with time-dependent control modulation. It has been commonly used in various quantum systems, such as solid-state spin system (NMR, NV centers) and superconducting qubits. DD usually involves periodic pulse sequences that can average out the system-environment interaction. Common DD sequences include spin echo, CPMG, XY8 etc.

In the idle time of a quantum circuit, DD can be applied to protect the coherence of qubits by decoupling the interaction with environment. It can efficiently prolong the qubit lifetime (e.g. from T2* to T2). To this end, DD could be a error mitigation tool that one can consider adding to the quantum circuit.

Proposed Solution

In general, DD requires access to control pulses, but for certain backends it can be realized with single-qubit gates such as RX and RY gates. Depending on the circuit, one may consider insert periodic π-pulses (using RX or RY) to suppress memory error and improve the circuit performance.

Additional References

In recent quantum error detection/detection experiments in Quantinuum's trapped ion device, they have been using DD to suppress memory errors:
https://arxiv.org/abs/2404.02280
https://journals.aps.org/prresearch/abstract/10.1103/PhysRevResearch.6.013221

[natestemen]

Thanks for opening this issue Changhao! Currently Mitiq does already support the use of dynamical decoupling through mitiq.ddd. Since we do not assume pulse-level access in Mitiq, we do digital dynamical decoupling by inserting sequences of gates into idle windows of a circuit. Currently we support 3 "native" sequences out of the box:

from mitiq.ddd.rules import xx, yy, xyxy

I think yesterday during our meeting you suggested adding a rule such as $SS$?

[purva-thakre]

I think yesterday during our meeting you suggested adding a rule such as SS?

What's the advantage of adding a SS rule?