The invention discloses a
measurement device independent
quantum key distribution system and method based on a W state. The
system comprises four
quantum terminal units and one
quantum terminal unit.Pulsed lasers of the four quantum terminal units transmit
laser of a specified
wavelength, the phase of [0, 2 phi] is randomly modulated by a phase modulator, horizontal, vertical, +45-degree or -45-degree polarization is randomly loaded by a
polarization controller, a
decoy state or a
signal state is marked by a strength modulator, and finally, the
laser is attenuated by an adjustable attenuatorto an average
photon number theoretically calculated and optimized and then transmitted to a quantum
relay unit. The quantum
relay unit performs W state projection measurement on signals transmitted through a
quantum channel; according to the response of a
detector, the quantum
relay unit publishes the measurement result, and two are randomly selected from the four quantum terminal units to publish quantum states; if the quantum states of the two are anti-dependent, the data is discarded; and if the quantum states of the two are dependent, the remaining two are bit-flipped to obtain a shared
password. The
system and the method for
quantum key distribution using the W state have better adaptability to the environment, and are low in cost by adopting mature basic linear optical components.