Korff B M R, Troppmann U, Kompa K L, de Vivie-Riedle R
Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching, Germany.
J Chem Phys. 2005 Dec 22;123(24):244509. doi: 10.1063/1.2141615.
Our concept for a quantum computational system is based on qubits encoded in vibrational normal modes of polyatomic molecules. The quantum gates are implemented by shaped femtosecond laser pulses. We adopt this concept to the new species manganese pentacarbonyl bromide [MnBr(CO)5] and show that it is a promising candidate in the mid-infrared (IR) frequency range to connect theory and experiment. As direct reference for the ab initio calculations we evaluated experimentally the absorption bands of MnBr(CO)5 in the mid-IR as well as the related transition dipole moments. The two-dimensional potential-energy surface spanned by the two strongest IR active modes and the dipole vector surfaces are calculated with density-functional theory. The vibrational eigenstates representing the qubit system are determined. Laser pulses are optimized by multitarget optimal control theory to form a set of global quantum gates: NOT, CNOT, Pi, and Hadamard. For all of them simply structured pulses with low pulse energies around 1 microJ could be obtained. Exemplarily for the CNOT gate we investigated the possible transfer to experimental shaping, based on the mask function for pulse shaping in the frequency regime as well as decomposition into a train of subpulses.
我们的量子计算系统概念基于多原子分子振动简正模式中编码的量子比特。量子门由整形飞秒激光脉冲实现。我们将这一概念应用于新物质五羰基溴化锰[MnBr(CO)₅]，并表明它是中红外（IR）频率范围内连接理论与实验的有前途的候选者。作为从头算计算的直接参考，我们通过实验评估了MnBr(CO)₅在中红外的吸收带以及相关的跃迁偶极矩。利用密度泛函理论计算了由两个最强红外活性模式跨越的二维势能面和偶极矢量面。确定了代表量子比特系统的振动本征态。通过多目标最优控制理论优化激光脉冲，以形成一组全局量子门：非门（NOT）、受控非门（CNOT）、π门（Pi）和哈达玛门（Hadamard）。对于所有这些门，都可以获得具有约1微焦低脉冲能量的简单结构脉冲。作为受控非门的示例，我们基于频率域中脉冲整形的掩模函数以及分解为一系列子脉冲，研究了向实验整形的可能转换。
