Abstract: There is presented optical interferometer apparatus for generating at least a first and a second state for each of at least two different quantum cryptographic basis sets and associated methods for operating the apparatus. First and a second interferometer arm paths and at least two interferometer output paths are provided. Each of the first and second interferometer arm paths; and the first and second optical output paths comprises a controllable phase modulator for controllably changing the phase of light propagating along the respective paths. This maybe a silicon carrier depletion phase modulator. The output from the controllable phase modulators of the first and second optical output paths are used together for defining each of the first and second states for each respective basis set. In some examples at least one of the interferometer arm paths comprises a further controllable phase modulator such as a thermo-optic phase modulator.

Abstract: There is provided an integrated-optic transmitter for transmitting light pulses to a further optical apparatus for generating a quantum cryptographic key according to at least one quantum cryptography technique. There is also provided an integrated-optic receiver for generating a quantum cryptographic key from light pulses received from a further optical apparatus. The transmitter apparatus splits incoming light into two paths to temporally separate the split light pulses and controls the output intensity of each split pulse as well as the phase of at least one of the split pulses. The receiver apparatus receives first and second light pulses and controls the output intensity of each said pulse between a first and a second optical detector. The light input into the second detector passes through an integrated element that controls the amount of light output into two paths that recombine before at least a portion is output to the second detector.

Abstract: There is presented optical interferometer apparatus for generating at least a first and a second state for each of at least two different quantum cryptographic basis sets and associated methods for operating the apparatus. First and a second interferometer arm paths and at least two interferometer output paths are provided. Each of the first and second interferometer arm paths; and the first and second optical output paths comprises a controllable phase modulator for controllably changing the phase of light propagating along the respective paths. This maybe a silicon carrier depletion phase modulator. The output from the controllable phase modulators of the first and second optical output paths are used together for defining each of the first and second states for each respective basis set. In some examples at least one of the interferometer arm paths comprises a further controllable phase modulator such as a thermo-optic phase modulator.

Abstract: There is provided an integrated-optic transmitter for transmitting light pulses to a further optical apparatus for generating a quantum cryptographic key according to at least one quantum cryptography technique. There is also provided an integrated-optic receiver for generating a quantum cryptographic key from light pulses received from a further optical apparatus. The transmitter apparatus splits incoming light into two paths to temporally separate the split light pulses and controls the output intensity of each split pulse as well as the phase of at least one of the split pulses. The receiver apparatus receives first and second light pulses and controls the output intensity of each said pulse between a first and a second optical detector. The light input into the second detector passes through an integrated element that controls the amount of light output into two paths that recombine before at least a portion is output to the second detector.