  Temporal cavity solitons are optical pulses that propagate indefinitely in
nonlinear resonators. They are currently attracting a lot of attention, both
for their many potential applications and for their connection to other fields
of science. Cavity solitons are phase locked to a driving laser. This is what
distinguishes them from laser dissipative solitons and the main reason why they
are excellent candidates for precision applications such as optical atomic
clocks. To date, the focus has been on driving Kerr solitons close to their
carrier frequency, in which case a single stable localised solution exists for
fixed parameters. Here we experimentally demonstrate, for the first time, Kerr
cavity solitons excitation around twice their carrier frequency. In that
configuration, called parametric driving, two solitons of opposite phase may
coexist. We use a fibre resonator that incorporates a quadratically nonlinear
section and excite stable solitons by scanning the driving frequency. Our
experimental results are in excellent agreement with a seminal amplitude
equation, highlighting connections to hydrodynamic and mechanical systems,
amongst others. Furthermore, we experimentally confirm that two different
phase-locked solitons may be simultaneously excited and harness this
multiplicity to generate a string of random bits, thereby extending the pool of
applications of Kerr resonators to random number generators and Ising machines.
