Geometric echo of a purゃ ly geometric spin qubitin diamond Yuhei Sekittuchi,Yusuke Komura,Shota Mishima,Touta Tanaka,Naeko Nllkura and Hideo Kosaka 7夕 乃 筋 んαttα 」 吻才 ″ οれ冴 助 ルタ浴 ブ づ 抑 筋wα 筋 ち rrO冴 θgヮ α,乃 ゎ 乃αttα 2イ θ-8jθ F,乃 ″ 乃 物 An electron spin can be a purcly gcometric qubit that has exclusively a geometric phase、 vhen the systenl is degenerate.In contrast that the conventional dynattlic qubit requires an energy gap to be controlled,geomctric qubit does not in principlco Wc hcrc show the geometric phase control of a purely geometric qubit in a degenerate sllbspace of a V― type spin l clectronic fleld system of a nitrogen vacancy center in diamond under zero lnagnctic fleld[1].The zero口 split state serves as an ancillary state to interact with a contro■ ing microwave(Fig。 (の ).The degenerate qubit operation is achieved by changing the geometric phasc of the Hlicrowave一 deaned bright state whlle leaving tlle dark state unchanged[2].We demOnstrate geometric spin echo to rё covcr thc geomctric spin coherence attcr 100 til■ es ofthe free induction dccay (Fig.(b)).Dependence ofthc ccho signal on the axial magnctic flcld indicates that correlation betwecn spin bath is the mttor decOherence source and minimized under zero magnctic neld. 1lved lncmory.The The demonstration reveals the importance ofthe spin degeneracy for long‐ degenerate geometric qubit is not only resilient to environmental noise but also robust against control error and free from dynalmic phase locking. (の IB〉 ID〉 一ュこ と一 りＥけど ５ 庄 Dark state ， Ｃ コＬ 今コ． 何︶ふこのＥＱ一 Bright state 40 80 Totalfree evolutlon ttme(Ps) The energy level diagral■ of a groLllld State 91ectron spin system in an■ lV center in diamond. Inset illustrates the geometric spin bit― nip operation in degenerate space as a result of27E rOtation from Fig。 (の tlle brigllt state lB〉 thrOugh the ancllla state O〉 。(b)Geometric spin free induction decay(Ralnsey interference)and geOmetric spin echo.Inset shows refocused echo sigllal ater 70μ s offree evolLltlon. [1]H.Kosaka and N.Nlikura,Entangled absorption of a single photon with a single spin in diamond. PめS,沢 タツ.Zθ ″.114,053603(2015). [2]H.Kosaka ctt α ア .Spin state tomograptt of optically上 物/2 Jected electrons in a semiconductor.ハ吻 457,702-705(2009). SpinTech VIII Basel,Aug.lo-13,2015 208 Posters B
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