Development of wave-packet interference control with an attosecond accuracy and is application to quantum computing

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Quantum phase manipulation of wave functions opens a novel technology through "coherent control" such as quantum computing and bond selective chemistry. One promising approach is to use coherent light to modulate a wave function with its optical phase. For example, irradiating a diatomic molecule with a femtosecond (fs) optical pulse, with bandwidth broad enough to cover several vibrational eigenstates, coherently superpose those eigenstates to yield a spatially localized wave function called a nuclear "wave packet (WP)" traveling back and forth along the bond axis. In the generalon of this WP, the phase of an optical field is imprinted on the WP as its quantum phase. Hence engineering the optical phase with an accuracy better than the optical cycle allows us to engineer the phase of the WP with the same accuracy.We have developed the "attosecond phase modulator", by which we can manipulate the relative phase of two fs laser pulses with an accuracy of 7 attoseconds. This phased pair of fs laser pulses has been used to realize unprecedented high-resolution interference of two nuclear WP's moving in a single Hg-Ar molecule where its fringe contrast is almost 100 %, demonstrating a pure wave nature of heavy particles.This high-resolution WP interference has been utilized to encode 9 typical trinary codes into a 3 tritquantum reglster assembled within a single molecule as nodal patterns of a WP. In principle it can be used for fhe storage of the phase information contained in an optical field. Moreover, by using this WP interference control, we have developed a high-precision phase shiffer operated on a qubitorqutrit composed of coherent superposition of two or three vibrational eigenstates within a single molecule. The present studies indicate a possibility of large-sale quantum computing using many vibrational eigenstates within a single molecule.