  Chirality is at the origin of life and is ubiquitous in nature. An object is
deemed chiral if it is non-superimposable with its own mirror image. This
relates to how circularly polarized light interacts with such object, a
circular dichroism, the differential absorption of right and left circularly
polarized light. According to the common understanding in biology, chemistry
and physics, the circular dichroism results from an internal chiral structure
or external symmetry breaking by illumination. We show that circular dichroism
is possible with simple symmetric optical nanoantennas at symmetric
illumination. We experimentally and theoretically demonstrate that two
electromagnetic dipole-like modes with a phase lag, in principle, suffice to
produce circular dichroism in achiral structure. Examples of the latter are all
visible spectrum optical nanoantennas, symmetric nanoellipses and nanodimers.
The simplicity and generality of this finding reveal a whole new significance
of the electromagnetic design at a nanoscale with potential far reaching
implications for optics in biology, chemistry and materials science.
