Accuracy of gates in a quantum computer based on vibrational eigenstates

Abstract

A model is developed to study the properties of a quantum computer that uses vibrational eigenstates of molecules to implement the quantum information bits and shaped laser pulses to apply the quantum logic gates. Particular emphasis of this study is on understanding how the different factors, such as properties of the molecule and of the pulse, can be used to affect the accuracy of quantum gates in such a system. Optimal control theory and numerical time-propagation of vibrational wave packets are employed to obtain the shaped pulses for the gates NOT and Hadamard transform. The effects of the anharmonicity parameter of the molecule, the target time of the pulse and of the penalty function are investigated. Influence of all these parameters on the accuracy of qubit transformations is observed and explained. It is shown that when all these parameters are carefully chosen the accuracy of quantum gates reaches 99.9%.

Implementation of simple logic gates on gold–ammonia bonding patterns in different charge states

“…Encoding classical bits into bonds is somewhat analogous to the approach known as vibrational quantum computing [35][36][37][38] in the sense that it requires addressable bonds (which each corresponds to a vibrational mode) as the inputs to the logic gate. The difference is that in our approach, the changes of the bonding patterns due to an external perturbation (charge alternation or optical excitation) implement the logic gate, not the transitions within the vibrational manifold induced by external IR laser pulses as is the case in vibrational quantum computing.…”

Comment on “Anharmonic properties of the vibrational quantum computer” [J. Chem. Phys. 126, 204102 (2007)]

“…2͑b͒, upper row͔ similar in intensity and structure to the one presented previously by Babikov in Ref. 10. Due to the low curvature but strong slope of the dipole moment at the equilibrium geometry, the maximum pulse intensity is only 0.005 a.u., the overtone peak in the corresponding spectrum is small.…”

Simulation of the elementary evolution operator with the motional states of an ion in an anharmonic trap

“…The evolution of |Φ(z,t)| 2 after successive applications of U(t pulse ) with the field E P (t) [Eq. (25)] is shown in Fig. 2.…”