We introduced Quantum State Holography, a novel technique for the reconstruction of quantum superposition states (wave packets). In analogy to the ordinary optical holography, the object wave function to be measured is allowed to interfere with a known reference wave function. For this purpose, we employ a sequence of two time-delayed laser pulses that consecutively excite the object and the reference wave packet in the excited molecular (or atomic) states. The total incoherent fluorescence of the excited molecule is recorded as the function of the delay time and serves as a “hologram”. We showed that these data contain enough information to extract the full quantum state of the object wave packet. Moreover, we developed a COIN variant of quantum holography, which is able to reconstruct coherent atomic and molecular states even in the presence of the phase noise at the excitation and detection stages of the procedure. Quantum Holography (combined with key elements of the COIN approach) was first used by the group of P. Bucksbaum in their reconstruction of Rydberg electronic wave packets (Phys.Rev. Lett. 81, 3050 (1998); Nature 397: (6716), 233 (1999)). By incorporating quantum holographic measurement in a closed feedback loop control scheme, they demonstrated optical preparation of the sculpted electronic wave packets with arbitrary "on-demand" pre-defined phase and amplitude characteristics.
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