Editing Quantum decoherence (section)

==== Dynamical Decoupling ====
'''[[Dynamical decoupling|Dynamical Decoupling]]''' (DD) is another typical [[quantum control]] technique used against decoherence, especially for systems that are coupled to noisy environments. DD involves applying an external sequence of control pulses to the quantum system at strategically timed intervals to average out environmental interactions. This technique effectively manipulates the irreversible component of quantum systems interact with surrounding environment by the external controllable interactions.<ref>{{Cite journal |last1=Viola |first1=Lorenza |last2=Knill |first2=Emanuel |last3=Lloyd |first3=Seth |date=1999-03-22 |title=Dynamical Decoupling of Open Quantum Systems |url=https://link.aps.org/doi/10.1103/PhysRevLett.82.2417 |journal=Physical Review Letters |language=en |volume=82 |issue=12 |pages=2417–2421 |doi=10.1103/PhysRevLett.82.2417 |arxiv=quant-ph/9809071 |bibcode=1999PhRvL..82.2417V |issn=0031-9007}}</ref> Dynamical decoupling has been experimentally demonstrated in various systems, including trapped ions<ref>{{Cite journal |last1=Biercuk |first1=Michael J. |last2=Uys |first2=Hermann |last3=VanDevender |first3=Aaron P. |last4=Shiga |first4=Nobuyasu |last5=Itano |first5=Wayne M. |last6=Bollinger |first6=John J. |date=2009-06-25 |title=Experimental Uhrig dynamical decoupling using trapped ions |url=https://link.aps.org/doi/10.1103/PhysRevA.79.062324 |journal=Physical Review A |language=en |volume=79 |issue=6 |page=062324 |doi=10.1103/PhysRevA.79.062324 |arxiv=0902.2957 |bibcode=2009PhRvA..79f2324B |issn=1050-2947}}</ref> and superconducting qubits.<ref>{{Cite journal |last1=Jurcevic |first1=Petar |last2=Javadi-Abhari |first2=Ali |last3=Bishop |first3=Lev S |last4=Lauer |first4=Isaac |last5=Bogorin |first5=Daniela F |last6=Brink |first6=Markus |last7=Capelluto |first7=Lauren |last8=Günlük |first8=Oktay |last9=Itoko |first9=Toshinari |last10=Kanazawa |first10=Naoki |last11=Kandala |first11=Abhinav |last12=Keefe |first12=George A |last13=Krsulich |first13=Kevin |last14=Landers |first14=William |last15=Lewandowski |first15=Eric P |date=2021-03-17 |title=Demonstration of quantum volume 64 on a superconducting quantum computing system |url=http://dx.doi.org/10.1088/2058-9565/abe519 |journal=Quantum Science and Technology |volume=6 |issue=2 |pages=025020 |doi=10.1088/2058-9565/abe519 |arxiv=2008.08571 |bibcode=2021QS&T....6b5020J |issn=2058-9565}}</ref> Here are some examples of representative sequences.

* [[Spin echo|Spin Echo]] (SE): SE is the consisting of a single π-pulse, which inverts the state of system.{{cn|date=December 2024}}

* Periodic Dynamical Decoupling (PDD): Applying control pulse periodically, PDD averages out the influence of the environment and decoupling the qubit.<ref>{{Cite journal |last1=Viola |first1=Lorenza |last2=Lloyd |first2=Seth |date=1998-10-01 |title=Dynamical suppression of decoherence in two-state quantum systems |url=https://link.aps.org/doi/10.1103/PhysRevA.58.2733 |journal=Physical Review A |language=en |volume=58 |issue=4 |pages=2733–2744 |doi=10.1103/PhysRevA.58.2733 |arxiv=quant-ph/9803057 |bibcode=1998PhRvA..58.2733V |issn=1050-2947}}</ref>

* Carr-Purcell-Meiboom-Gill (CPMG) Sequence:<ref>{{Cite journal |last1=Meiboom |first1=S. |last2=Gill |first2=D. |date=1958-08-01 |title=Modified Spin-Echo Method for Measuring Nuclear Relaxation Times |url=http://dx.doi.org/10.1063/1.1716296 |journal=Review of Scientific Instruments |volume=29 |issue=8 |pages=688–691 |doi=10.1063/1.1716296 |bibcode=1958RScI...29..688M |issn=0034-6748}}</ref> CPMG is an extension of SE. It applies a series of π-pulses.