Science6,1129(2015)Probing Johnson noise and ballistic transport in normal metals with a single-spin qubit

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1、RESEARCH

2、REPORTSQUANTUMELECTRONICSspatial,andtemperaturedependenceofJohnsonnoiseemanatingfromconductors.ThemagneticJohnsonnoiseresultsinareductionofthespinProbingJohnsonnoiseandballisticlifetimeofindividualNVelectronicspins,therebyallowingustoprobetheintrinsicpropertiesoftransportinnormalmetalsw

3、ithatheconductornoninvasivelyoverawiderangeofparameters.Individual,opticallyresolvableNVcentersareimplanted∼15nmbelowthesingle-spinqubitsurfaceofa∼30-mm-thickdiamondsample.Asilverfilmisthendepositedorpositionedon111,2211thediamondsurface(Fig.1A).Thespinsub-S.Kolkowitz,*A.Safira,*A.A.High,R.C.Dev

4、lin,S.Choi,Q.P.Unterreithmeier,D.Patterson,1A.S.Zibrov,1V.E.Manucharyan,3H.Park,1,2†M.D.Lukin1†levelsjms¼0〉andjms¼T1〉oftheNVelectronicgroundstateexhibitazero-fieldsplittingofThermallyinducedelectricalcurrents,knownasJohnsonnoise,causefluctuatingelectricandD¼2p2:88GHz(17–20).Therelaxationratesma

5、gneticfieldsinproximitytoaconductor.Thesefluctuationsareintrinsicallyrelatedtothebetweenthejms¼0〉andjms¼T1〉statespro-conductivityofthemetal.Weusesingle-spinqubitsassociatedwithnitrogen-vacancycentersinvideasensitiveprobeofthemagneticfieldnoisediamondtoprobeJohnsonnoiseinthevicinityofconductivesi

6、lverfilms.MeasurementsofatthetransitionfrequencieswT¼DT2gmBBjj,polycrystallinesilverfilmsoverarangeofdistances(20to200nanometers)andtemperatureswhereBjjisthemagneticfieldalongtheNV(10to300kelvin)areconsistentwiththeclassicallyexpectedbehaviorofthemagneticaxis,g≈2istheelectrong-factor,andmBisthef

7、luctuations.However,wefindthatJohnsonnoiseismarkedlysuppressednexttosingle-crystalBohrmagneton(21,22)(Fig.1B).films,indicativeofasubstantialdeviationfromOhm’slawatlengthscalesbelowtheelectronmeanTheimpactofJohnsonnoiseemanatingfromfreepath.Ourresultsareconsistentwithageneralizedmodelthataccounts

8、fortheballisticmotionapolycrystallinesilverfilmdepositedontheofelectronsinthemetal,indicatingthatundertheappropriateconditions,nearbyelectrodesmaydiamondsurface(Fig.1C)isevidentwhencom-beusedforcontrollingnanoscaleoptoelectr