Quantum Remnant as Dark Energy and Dark Matter

We study the quantum remnant of a scalar field protected by the uncertainty principle. The quantum remnant that survived the later stage of evolution of the universe may provide dark energy and dark matter depending on the potential. Though the quantum remnant shares some useful property of complex scalar field (spintessence) dark energy model, % However although it avoids the formation of Q-ball, quantum fluctuations are still unstable to the linear perturbations for $V \sim \phi^q$ with $q<1$ as in the spintessence model.