  We put forward the concept of work extraction from thermal noise by
phase-sensitive (homodyne) measurements of the noisy input followed by
(outcome-dependent) unitary manipulations of the post-measured state. For
optimized measurements, noise input with more than one quantum on average is
shown to yield heat-to-work conversion with efficiency and power that grow with
the mean number of input quanta, detector efficiency and its inverse
temperature. This protocol is shown to be advantageous compared to common
models of information and heat engines.
