[Problem] A method, a device, a system and a program that can adjust the drive timing of a photon detector with high speed and high reliability is provided. [Solution] A timing adjustment device for adjusting timing for driving a photon detector (202) of a receiver (200), includes: an asymmetric interferometer (201) that inputs an optical pulse sequence from a sender (100) and outputs an interference output optical pulse to the photon detector (202), wherein the optical pulse sequence includes two consecutive pulses, the sender subjecting the two consecutive pulses to phase-modulation according to send data fixed to a predetermined bit value, wherein the interference output optical pulse is generated by the two consecutive pulses interfering with each other depending on a phase difference, and wherein the interference output optical pulse is output to the photon detector corresponding to the phase difference; and a controller (204) configured to: record photon counts of photons detected by the photon detector while shifting gate application timing for the photon detector over a predetermined range; and set gate application timing for the photon detector with reference to a timing indicating a peak value of the photon counts.