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1、Chin.Phys.BVol.26,No.1(2017)010601Optimalquantumparameterestimationoftwo-qutritHeisenberg??chainunderdecoherenceHong-yingYang(杨洪应)1,QiangZheng(郑强)2,†,andQi-junZhi(支启军)1,‡1SchoolofPhysicsandElectronics,GuizhouNormalUniversity,Guiyang550001,China2SchoolofMathematics,GuizhouNor
2、malUniversity,Guiyang550001,China(Received11January2016;revisedmanuscriptreceived19September2016;publishedonline30November2016)AdoptingtheMilburndecoherencemodel,weinvestigatetheperformanceofquantumFisherinformationofthetwo-qutritisotropicHeisenbergXYchainunderdecoherence.Wefi
3、ndthatthequantumFisherinformationwithrespecttothedecoherencerateandthemagneticfielddecreasesexponentiallyinthelong-timelimit,whichsignificantlyreducestheprecisionofoptimalquantumestimation.Wealsoshowthatwiththeincreaseofthedecoherencerateorthemagneticfield,theQFIsgodownconsidera
4、bly.Furthermore,wefindthattheprecisionofoptimalquantumestimationcanbeenhancedbytheentanglementintheinputstate.Keywords:intrinsicdecoherence,quantumFisherinformation,spinchainPACS:06.20.–f,03.65.Yz,42.50.DvDOI:10.1088/1674-1056/26/1/0106011.Introductionspecttothedecoherencerate
5、andthemagneticfieldstrength[1,2]increasewiththetimeintheinitialevolution,anddecreaseex-Quantummetrology,investigatingthelimitofthepre-ponentiallyinthelong-timelimit.Wealsoshowthatwiththecisionofparameterestimationboundedbyquantummechan-increaseofthedecoherencerateorthemagnetic
6、field,theQFIsics,hasexcitedwideinterestrecently.[3–9]QuantumFisherin-godownconsiderably.Inaddition,wedisplaythattheestima-formation(QFI)playsanimportantroleinquantummetrol-tionprecisioncanbeenhancedbythedegreeoftheentangle-ogy.AccordingtothequantumCramer–Raoinequality,´[10]men
7、tintheinputstate,whichisconsistentwiththeresultsinQFIdeterminesthelowerboundofthevarianceoftheunbi-Refs.[23]and[24].asedestimatorforaparameter.[10,11]Moreover,QFIhasalsoThepaperisorganizedasfollows.Inthenextsection,beenappliedinquantumfrequencystandards,[12]detectionwereviewt
8、hemainaspectsoftheQFI.InSection3,wead-ofentanglement,[13]probingtheq
