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arXiv:1411.6566 · Physical Review A

Nontrivial excited-state coherence due to two uncorrelated partially coherent fields

Z. S. Sadeq

Published Apr 30, 2015• 0 citations
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Abstract

We analyze a model where a closed $V$ system is excited by two uncorrelated partially coherent fields. We use a collisionally broadened cw laser, which is a good model for an experimentally realizable partially coherent field, and show that it is possible to generate excited-state coherences even if the two fields are uncorrelated. This transient coherence can be increased if splitting between the excited states is reduced relative to the radiation coherence time ${\ensuremath{\tau}}_{d}$. For small excited-state splitting, one can use this scheme to generate a long-lived coherent response in the system.

DOI
10.1103/physreva.91.043847

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We analyze a model where a closed VVV system is excited by two uncorrelated partially coherent fields. We use a collisionally broadened cw laser, which is a good model for an experimentally realizable partially coherent field, and show that it is possible to generate excited-state coherences even if the two fields are uncorrelated. This transient coherence can be increased if splitting between the excited states is reduced relative to the radiation coherence time \ensuremathτd{\ensuremath{\tau}}_{d}\ensuremathτd​. For small excited-state splitting, one can use this scheme to generate a long-lived coherent response in the system.
We investigate quantum coherences between excited states induced on quantum systems upon excitation by partially coherent radiation sources. Attempts at rejuvenating coherences using noisy sources are also explored. This work is most relevant to studies of photo-excitation of light harvesting systems under natural conditions as well as to quantum optical experiments using partially coherent lasers. The transient coherent response of a model VVV system upon irradiation by various models of incoherent light is explored and it was found that it was possible to induce transient excited state coherences upon excitation. These excited state coherences eventually become a small fraction of population and the system reaches a mixed state. Lastly, we critique an existing literature model of excitation by noisy laser and we show that the coherence observed in that scenario is artificial. We propose an alternative using a physical model of noisy excitation.
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Abstract\nWe consider a dual ?-system under double laser excitation to investigate the possibility of indirect coherence transfer between atomic ground states through an excited state. The atomic system is excited by a frequency modulated pump laser and probed by a low-power cw laser. All the decoherence mechanisms are discussed and taken into account. Adjustment of parameters of the two radiations aimed at maximization of coherence transfer is addressed. The study can help to understand phenomena as collisional transfer of coherence and can find application in the experimental realization of atomic sensors.
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Reinvigorating Excited State Coherences in VVV Level Systems with the use of Trap States
We investigate potential schemes to reinvigorate coherences between excited states in a VVV level system under various excitation conditions. Coherent pulsed, cw and noisy pulsed excitation are considered and the existence of a trap state is shown to allow for the resurgence of excited state coherence in the two pulsed scenarios. With a short trap time (strong decoherence), it is possible to restart excited state coherence in the pulsed scenarios. In the case of cw excitation with relaxation back to the ground state, the coherences between the excited states do not vanish in the long time limit but instead approach a non-zero value.