  Future experiments at high energy $e^+e^-$ colliders will focus on extremely
precise Standard Model measurements. Among the most important physics
benchmarks, there is the capability to resolve the Higgs decays into W or Z
pairs, in their completely hadronic decay modes (4 jets in the final state),
only based on the invariant mass of the jet pair coming from decay of the
on-shell boson. This translates into a relative energy resolution target of
$30\%/\sqrt{E}$, well beyond current detector performances. Dual-readout
calorimetry is a technique which aims to improve the energy resolution, for
single hadrons and hadronic jets, exploiting the information produced by two
different physical processes, namely scintillation and Cerenkov light emission.
The IDEA detector, whose concept has been included in both the FCC and CEPC
Conceptual Design Reports, is based on a dual-readout fibre calorimeter with
independent fibre readout exploiting Silicon PhotoMultipliers (SiPMs). The
individual SiPM information will be beneficial for a highly granular
calorimeter design, opening up to advanced reconstruction techniques such as
Particle Flow and a variety of neural network algorithms. In this paper the
status of calorimeter prototypes that have been developed to demonstrate the
feasibility of the dual-readout method in association with the high granularity
feature is illustrated. The specific choice for the design of each prototype is
presented, together with the performances achieved at high-energy test beams or
through simulations.
