Short answer: Dynamical decoupling (DD) protects qubits from a noisy environment by applying a sequence of flips that averages the qubit-environment coupling to zero. A review in Frontiers of Physics calls it a promising strategy that is compatible with other desired functionalities, such as quantum gates. This article summarises two review articles and describes the idea, not any particular device.
The problem
A Colloquium in Reviews of Modern Physics, aimed at newcomers, says quantum technologies are useful only if the quantum systems also interact with their environment, and that those interactions can degrade properties such as coherence and entanglement. It says the interaction must therefore be controlled so that the unwanted effects of the environment are suppressed while the necessary interactions are retained. It says the dominant contribution to loss of information is pure dephasing, the loss of coherence in superposition states, so most schemes for reducing information loss focus on dephasing, as does the Colloquium.
The idea behind dynamical decoupling
The Frontiers of Physics review says that in quantum information processing it is vital to protect the coherence of qubits in noisy environments. It describes DD as applying a sequence of flips on qubits and averaging the qubit-environment coupling to zero. The Colloquium describes a family of techniques developed in different areas of physics, including magnetic resonance, optics and quantum information, which apply static or time-dependent fields to the quantum system, designed to average the effect of the environmental interactions to zero.
What the review covers
The Frontiers review says it covers recent progress in the theory of DD and in experimental demonstrations. It gives semiclassical and quantum descriptions of qubit decoherence due to coupling to noisy environments, and from the quantum picture presents a geometrical interpretation of DD. It reviews periodic Carr-Purcell-Meiboom-Gill DD and concatenated DD. It then explores Uhrig DD, which it says employs the least number of pulses in an unequally spaced sequence to suppress the qubit-environment coupling to a given order of the evolution time.
Other protection methods
The Colloquium places DD alongside other approaches. It says quantum error correction schemes were developed to detect and eliminate certain errors during storage and processing of quantum information, and that in many physical systems it is useful to use specific quantum states that are intrinsically less susceptible to environmental noise to encode information. These are separate strategies from DD.
What this does not tell you
This article uses the abstracts of two review papers. It does not give pulse timings, error reductions or results for any platform, and it does not say that DD is used in any particular machine. Which sequence suits which noise is a detailed question for the reviews themselves.
FAQ
What is dynamical decoupling?
A sequence of flips on qubits that averages the qubit-environment coupling to zero, per the Frontiers of Physics review.
What noise does it target?
The Colloquium says the dominant contribution to information loss is pure dephasing, and most schemes, including its own focus, address dephasing.
Does it work with quantum gates?
The Frontiers review calls it compatible with other desired functionalities, such as quantum gates.
Which sequences exist?
The review covers periodic Carr-Purcell-Meiboom-Gill DD, concatenated DD and Uhrig DD.
Is it the same as error correction?
No. The Colloquium describes quantum error correction as a separate approach that detects and eliminates certain errors.
All field notes