Coherent coupling of a superconducting flux qubit to an electron spin ensemble in diamond

During the past decade, research into superconducting quantum bits (qubits) based on Josephson junctions has made rapid progress. Many foundational experiments have been performed, and superconducting qubits are now considered one of the most promising systems for quantum information processing. However, the experimentally reported coherence times are likely to be insufficient for future large-scale quantum computation. A natural solution to this problem is a dedicated engineered quantum memory based on atomic and molecular systems. The question of whether coherent quantum coupling is possible between such natural systems and a single macroscopic artificial atom has attracted considerable attention since the first demonstration of macroscopic quantum coherence in Josephson junction circuits. Here we report evidence of coherent strong coupling between a single macroscopic superconducting artificial atom (a flux qubit) and an ensemble of electron spins in the form of nitrogen-vacancy colour centres in diamond. Furthermore, we have observed coherent exchange of a single quantum of energy between a flux qubit and a macroscopic ensemble consisting of about 3?×?10(7) such colour centres. This provides a foundation for future quantum memories and hybrid devices coupling microwave and optical systems.     

量子谐振子与经典谐振子的比较

在Heisenberg表象,通过引入升降算符求解了量子谐振子,计算了任意初态情况下坐标、动量、动能、势能和哈密顿量的期望值,并同经典谐振子的相应力学量进行了比较,得出了量子谐振子只能在一定条件下趋近于经典谐振子而不可能等同。     

Spectrum of a superconducting phase qubit coupled to a microscopic two-level system

We measured experimentally the spectrum of a superconducting phase qubit. An avoided energy-level crossing is obviously observed, which is due to the coupling to a microscopic two-level system. With different theoretical methods, we simulated the spectrum, from which we can obtain the coupled system＇s parameters and the coupling mechanism.     

Spectrum of a superconducting phase qubit coupled to a microscopic two-level system

We measured experimentally the spectrum of a superconducting phase qubit. An avoided energy-level crossing is obviously observed, which is due to the coupling to a microscopic two-level system. With different theoretical methods, we simulated the spectrum, from which we can obtain the coupled system’s parameters and the coupling mechanism.     

三维各向同性谐振子的升降算符

利用特殊函数关系式以及算符r,1r,ddr对径向函数的作用结果, 得出三维各向同性谐振子的径向算符,便于求解力学量的平均值.重新定义其升降算符,便于求解矩阵元.     

N维各向同性谐振子的超对称量子力学

构造了一个特殊的超对称伙伴势V±(x),在形不变势条件下,用超对称量子力学(SQM)方法,得到了N维各向同性谐振子的能量本征值和本征函数.     

Identification of Markovian open system dynamics for qubit systems

We discuss the problem of identification of the dynamical generators for open two-level quantum systems in a Markovian environment.Based on Bloch sphere representation,the identification problem is converted to the estimation of a 3-dimensional real process matrix A and an inhomogeneous term c.The parameter identifiability and sufficient conditions for completely identification of A and c are obtained.Further discussion shows that the obtained sufficient conditions are not always necessary.The approach can be generalized to finite-level open quantum systems in an arbitary Markovian environment.     

对受迫振动暂态过程的分析

本文对受迫振动暂态过程的图象做了全面分析，用计算机代数系统－ＤＥＲＩＶＥ做出了有关图象，指出了国内一些物理学教科书中所描述的受迫振动暂态过程图象的错误。     

二维谐振子的双波函数描述

用双波函数的量子理论研究二维谐振子力学量的时间演化方程及经典近似 ,证明了二维各向同性谐振子角动量守恒     

经典谐振子的动量-位置不确定关系

推出了经典谐振子的动量-位置不确定关系,并且给出它和量子谐振子的不确定关系之间的对应关系.     

三维各向同性谐振子的量子数阶梯算符

三维各向同性谐振子的量子数阶梯算符查新未王天真（陕西师范大学物理学系，西安７１００６２；第一作者，男，３８岁，副教授）１三维各向同性谐振子的阶梯算符三维各向同性谐振子的哈米顿算符为Ｈ∧＝Ｐ∧２２μ＋１２μω２ｒ２，力学量Ｈ∧，Ｌ∧２，Ｌ∧Ｚ的共同本征...     

非对易相空间中带电谐振子的Wigner函数

从Moyal—Weyl乘法与Bopp变换出发,考虑了坐标-坐标、动量-动量的非对易性;利用非对易相空间量子力学的代数关系,讨论了非对易相空间中带电谐振子的Wigner函数,在所给出的非对易相空间带电谐振子的Wigner函数中出现了依赖于非对易参数的附加项。     

一维谐振子的能级宽度和能级寿命

推出一维谐振子的能级的能量不确定范围等于零,能级的平均寿命等于无穷大。     

用泛函Euler方程求解线性谐振子的基态能量和波函数

利用泛函数极值满足的Euler方程,解出了线性谐振子的基态能量和波函数,与传统的薛定谔方程相比,本方法运算简便,物理意义明确。     

电磁场中变频率谐振子的不变量和传播子以及波函数

本文依靠一特定的正则变换,用相空间路径积分方法,求得电磁场中变频率谐振子的不变量和传播子以及波函数。     

谐振子微扰的相似展开和能谱

文中采用直接将一般形式的微扰势在简谐定态最可几位置坐标附近做与简谐势相近似展开的方法,把简谐势和微扰近似展开式合并,得到修正的简谐势,以求解修正后的定态能谱。     

对称四弹性振子的二维非线性振动

本文应用拉格朗日方程方法研究了理想对称四弹性振子做二维运动的变化规律,得到其微小振动的控制方程,用数值解法求解出了振动方程,得到了振子运动的时程响应和轨迹图样．结果表明：理想对称四弹性振子的振动为非简谐运动,它的运动周期在其X方向和Y方向与振幅的大小成反比,但受振幅影响不大．波形与振幅无关,可看成是一个变形了的余弦波．     

Coherent control of optical information with matter wave dynamics

In recent years, significant progress has been achieved in manipulating matter with light, and light with matter. Resonant laser fields interacting with cold, dense atom clouds provide a particularly rich system. Such light fields interact strongly with the internal electrons of the atoms, and couple directly to external atomic motion through recoil momenta imparted when photons are absorbed and emitted. Ultraslow light propagation in Bose-Einstein condensates represents an extreme example of resonant light manipulation using cold atoms. Here we demonstrate that a slow light pulse can be stopped and stored in one Bose-Einstein condensate and subsequently revived from a totally different condensate, 160 mum away; information is transferred through conversion of the optical pulse into a travelling matter wave. In the presence of an optical coupling field, a probe laser pulse is first injected into one of the condensates where it is spatially compressed to a length much shorter than the coherent extent of the condensate. The coupling field is then turned off, leaving the atoms in the first condensate in quantum superposition states that comprise a stationary component and a recoiling component in a different internal state. The amplitude and phase of the spatially localized light pulse are imprinted on the recoiling part of the wavefunction, which moves towards the second condensate. When this 'messenger' atom pulse is embedded in the second condensate, the system is re-illuminated with the coupling laser. The probe light is driven back on and the messenger pulse is coherently added to the matter field of the second condensate by way of slow-light-mediated atomic matter-wave amplification. The revived light pulse records the relative amplitude and phase between the recoiling atomic imprint and the revival condensate. Our results provide a dramatic demonstration of coherent optical information processing with matter wave dynamics. Such quantum control may find application in quantum information processing and wavefunction sculpting.     

速度平方力作用下含时阻尼谐振子的不变量与完全对称群

对于速度平方力作用下的含时阻尼谐振子,我们依靠一特定坐标变换用Lewis与Leach所提出的直接方法求得其不变量,用扩张李群的方法获得其完全对称群。此外,我们用另一种方法依靠同样的特定坐标变换求得此完全对称群。