抛物势量子点中强耦合双极化子量子比特的性质
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摘要
基于LLP幺正变换,采用Pekar型变分法得到了二维量子点中强耦合双极化子的基态和第一激发态的能量和波函数,进而构造了一个双极化子的量子比特。数值结果表明:在量子比特内,两电子的空间几率密度的时间振荡周期T0随电声子耦合强度α、量子点的受限强度ω0以及介质的介电常数比η的增加而减小;在量子比特内,两电子的空间几率密度Q随时间t、角坐标φ2及介电常数比η的变化而作周期性振荡;两电子在量子点中心附近区域出现的几率较大,而在远离量子点中心区域出现的几率很小。
On the basis of Lee-Low-Pines( LLP) unitary transformation,the eigenenergy and eigenfunction of the ground-state and the first excited state of the strong-coupling bipolaron in two-dimensional quantum dot( QD) were obtained by using the variational method of Pekar type. A qubit was formed by overlaying both the ground state and the first excited state of the bipolaron system. Numerical calculations indicate that the oscillating period T0 of qubits decreases with the increasing the electron-phonon coupling strength α,the confinement strength ω0of the quantum dot,and the dielectric constant ratio η; the distribution of the probability density Q of the electrons in quantum dot oscillates periodically with time t,angle coordinate φ2,and the dielectric constant ratio η,and there is a maximum at near the center and zero away from the center of quantum dot.
On the basis of Lee-Low-Pines( LLP) unitary transformation,the eigenenergy and eigenfunction of the ground-state and the first excited state of the strong-coupling bipolaron in two-dimensional quantum dot( QD) were obtained by using the variational method of Pekar type. A qubit was formed by overlaying both the ground state and the first excited state of the bipolaron system. Numerical calculations indicate that the oscillating period T0 of qubits decreases with the increasing the electron-phonon coupling strength α,the confinement strength ω0of the quantum dot,and the dielectric constant ratio η; the distribution of the probability density Q of the electrons in quantum dot oscillates periodically with time t,angle coordinate φ2,and the dielectric constant ratio η,and there is a maximum at near the center and zero away from the center of quantum dot.
引文
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[18]额尔敦朝鲁,白旭芳,韩超.抛物量子点中强耦合磁双极化子内部激发态性质[J].物理学报,2014,63(2):027501-1-8.EERDUNCHAOLU,BAI X F,HAN C.Properties of the internal excited state of the strong-coupling magneto-bipolaron in a parabolic quantum dot[J].Acta Phys.Sinica,2014,63(2):027501-1-8.(in Chinese)
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[3]KANE B E.A silicon-based nuclear spin quantum computer[J].Nature,1998,393(6681):133-137.
[4]LOSS D,DIVINCENZO D P.Quantum computation with quantum dots[J].Phys.Rev.A,1998,57(1):120-126.
[5]KYRIAKIDIS J,PENNEY S J.Coherent rotations of a single spin-based qubit in a single quantum dot at fixed Zeeman energy[J].Phys.Rev.B,2005,71(12):125332-1-5.
[6]FURUTA S,BARNES C H W,DORAN C J L.Single-qubit gates and measurements in the surface acoustic wave quantum computer[J].Phys.Rev.B,2004,70(20):205320-1-12.
[7]LI S S,LONG G L,BAI F S,et al..Quantum computing[J].Proc.Nat.Acad.Sci.USA,2001,98(21):11847-11848.
[8]LI S S,XIA J B,LIU J L,et al..InA s/GaA s single-electron quantum dot qubit[J].J.Appl.Phys.,2001,90(12):6151-6155.
[9]YU Y F,LI W P,YIN J W,et al..The decoherence of single electron quantum dot qubit[J].Int.J.Theor.Phys.,2011,50(11):3322-3328.
[10]XIAO J L.The effect of electric field on an asymmetric quantum dot qubit[J].Quant.Inf.Proc.,2013,12(12):3707-3716.
[11]CHEN Y J,XIAO J L.The temperature effects on the parabolic quantum dot qubit in the electric field[J].J.Low Temp.Phys.,2013,170(1-2):60-67.
[12]SUN Y,DING Z H,XIAO J L.Effects of magnetic field on the coherence time of a parabolic quantum dot qubit[J].J.Low Temp.Phys.,2014,177(3-4):151-156.
[13]EERDUNCHAOLU,XIN W.Temperature dependence of the properties of strong-coupling bipolaron in a quantum dot[J].Phys.B,2011,406(3):358-362.
[14]XIAO J L.Properties of a strong coupling bipolaron in an asymmetric quantum dot[J].J.Low Temp.Phys.,2014,174(5-6):284-291.
[15]ZHAO Y W,HAN C,XIN W,et al..Spin polarization ground state of quasi-2D magneto-bipolarons in the strong-coupling limit[J].Superlattices Microstruct.,2014,74:198-205.
[16]LEE T D,LOW F E,PINES D.The motion of slow electrons in a polar crystal[J].Phys.Rev.,1953,90(2):297-302.
[17]YILDIRIM T,ERCELEBI A.The grounds-state description of the optical polaron versus the effective dimensionality in quantum-well-type systems[J].J.Phys.Condens.Matter,1991,3(10):1271-1277.
[18]额尔敦朝鲁,白旭芳,韩超.抛物量子点中强耦合磁双极化子内部激发态性质[J].物理学报,2014,63(2):027501-1-8.EERDUNCHAOLU,BAI X F,HAN C.Properties of the internal excited state of the strong-coupling magneto-bipolaron in a parabolic quantum dot[J].Acta Phys.Sinica,2014,63(2):027501-1-8.(in Chinese)