  One of the outstanding challenges to information processing is the eloquent
suppression of energy consumption in execution of logic operations. Landauer
principle sets an energy constraint in deletion of a classical bit of
information. Although some attempts have been paid to experimentally approach
the fundamental limit restricted by this principle, exploring Landauer
principle in a purely quantum mechanical fashion is still an open question.
Employing a trapped ultracold ion, we experimentally demonstrate a quantum
version of Landauer principle, i.e., an equality associated with energy cost of
information erasure in conjunction with entropy change of the associated
quantized environment. Our experimental investigation substantiates an intimate
link between information thermodynamics and quantum candidate systems for
information processing.
