An integrated optical circuit for an optical neural network, the optical circuit being configured: to process a phase-encoded optical input signal (S in); and to provide a phase-encoded optical output signal (S out) depending on the phase-encoded optical input signal (S in), the phase-encoded optical output signal emulating a synapse functionality with respect to the phase-encoded optical input signal (S in); the integrated optical circuit comprising: a reference waveguide configured to carry an optical reference signal (S r); an input waveguide configured to receive the phase-encoded optical input signal (S in), wherein a phase difference (φ) between the optical reference signal (S r) and the optical input signal (S in) represents the phase of the phase encoded optical input signal (S in); an output waveguide; an optical interferometer configured to convert the optical reference signal (S r) and the optical input signal (S in) into an interference signal by superimposition; a tunable attenuator configured to perform a weighting of the interference signal into a weighted interference signal; and a phase-shifting device configured to convert the weighted interference signal into the phase-encoded optical output signal (S out) by inducing a phase shift in the optical reference signal (S r) in dependence on the weighted interference signal. the optical circuit being configured: to process a phase-encoded optical input signal (S in); and to provide a phase-encoded optical output signal (S out) depending on the phase-encoded optical input signal (S in), the phase-encoded optical output signal emulating a synapse functionality with respect to the phase-encoded optical input signal (S in); to process a phase-encoded optical input signal (S in); and to provide a phase-encoded optical output signal (S out) depending on the phase-encoded optical input signal (S in), the phase-encoded optical output signal emulating a synapse functionality with respect to the phase-encoded optical input signal (S in); the integrated optical circuit comprising: a reference waveguide configured to carry an optical reference signal (S r); an input waveguide configured to receive the phase-encoded optical input signal (S in), wherein a phase difference (φ) between the optical reference signal (S r) and the optical input signal (S in) represents the phase of the phase encoded optical input signal (S in); an output waveguide; an optical interferometer configured to convert the optical reference signal (S r) and the optical input signal (S in) into an interference signal by superimposition; a tunable attenuator configured to perform a weighting of the interference signal into a weighted interference signal; and a phase-shifting device configured to convert the weighted interference signal into the phase-encoded optical output signal (S out) by inducing a phase shift in the optical reference signal (S r) in dependence on the weighted interference signal. a reference waveguide configured to carry an optical reference signal (S r); an input waveguide configured to receive the phase-encoded optical input signal (S in), wherein a phase difference (φ) between the optical reference signal (S r) and the optical input signal (S in) represents the phase of the phase encoded optical input signal (S in); an output waveguide; an optical interferometer configured to convert the optical reference signal (S r) and the optical input signal (S in) into an interference signal by superimposition; a tunable attenuator configured to perform a weighting of the interference signal into a weighted interference signal; and a phase-shifting device configured to convert the weighted interference signal into the phase-encoded optical output signal (S out) by inducing a phase shift in the optical reference signal (S r) in dependence on the weighted interference signal.