Spontaneous symmetry breaking in coherently driven-dissipative coupled nanocavities

Spontaneous symmetry breaking (SSB) is a fundamentally important process that underlies many outstanding physical phenomena, such as phase transitions in metamaterials, and that can be exploited for a wide variety of applications. In particular, SSB has been observed in single coherently driven micro or macro ring resonators, where it respectively occurs between the forward and the counter propagative waves [1] , and between the two elliptically polarized components of the resonator [2] , and it has notably been proposed for new computing schemes. Nanodevices constitute a highly promising platform that could be harnessed for targeting a reduction of the photon number or improved integration capacity. SSB has recently been observed in evanescently coupled nanolasers, incoherently driven above the laser threshold, as the breaking of the mirror (or left/right) symmetry [3] . However, incoherent pumping suffers from thermal noise and a lack of control since the only control parameter is the pumping level in the nanolaser system, whereas the detuning can also be changed in the coherently driven system. In addition, most theoretical developments on few photon SSB in nonlinear coupled cavities have been carried out in a coherently driven-dissipative framework and have notably predicted important quantum features such as entanglement [4] . These driven-dissipative nonlinear coupled-cavity models constitute a paradigm of open quantum systems. Importantly, SSB in a coherently driven-dissipative system has not been demonstrated to date.