  Integrated sensing and communication (ISAC) has attracted much attention as a
promising approach to alleviate spectrum congestion. However, traditional ISAC
systems rely on phased arrays to provide high spatial diversity, where enormous
power-consuming components such as phase shifters are used, leading to the high
power consumption of the system. In this article, we introduce holographic
ISAC, a new paradigm to enable high spatial diversity with low power
consumption by using reconfigurable holographic surfaces (RHSs), which is an
innovative type of planar antenna with densely deployed metamaterial elements.
We first introduce the hardware structure and working principle of the RHS and
then propose a novel holographic beamforming scheme for ISAC. Moreover, we
build an RHS-enabled hardware prototype for ISAC and evaluate the system
performance in the built prototype. Simulation and experimental results verify
the feasibility of holographic ISAC and reveal the great potential of the RHS
for reducing power consumption. Furthermore, future research directions and key
challenges related to holographic ISAC are discussed.
