Abstract: An optical device for a quantum random number generator comprising: a source of phase randomised pulses of light, the source of phase randomised pulses of light further comprising a plurality of gain-switched lasers, each gain-switched laser having an output, and each gain-switched laser being configured to emit a stream of pulses such that the phase of each pulse in the stream of pulses is randomised, and an optical pulse combiner, the optical pulse combiner being configured to receive streams of pulses from the output of each gain-switched laser, combine the streams of pulses with one another into a combined stream of pulses and direct the combined stream of pulses into at least one output of the optical pulse combiner, the at least one output of the optical pulse combiner being the output of the source of phase randomised pulses of light; wherein the source of phase randomised pulses of light is configured such that the streams of pulses of light emitted by the plurality of gain-switched lasers are tem

Abstract: An optical device for a quantum random number generator comprising: a source of phase randomised pulses of light, the source of phase randomised pulses of light further comprising a plurality of gain-switched lasers, each gain-switched laser having an output, and each gain-switched laser being configured to emit a stream of pulses such that the phase of each pulse in the stream of pulses is randomised, and an optical pulse combiner, the optical pulse combiner being configured to receive streams of pulses from the output of each gain-switched laser, combine the streams of pulses with one another into a combined stream of pulses and direct the combined stream of pulses into at least one output of the optical pulse combiner, the at least one output of the optical pulse combiner being the output of the source of phase randomised pulses of light; wherein the source of phase randomised pulses of light is configured such that the streams of pulses of light emitted by the plurality of gain-switched lasers are tem

Abstract: An apparatus for measuring an input signal, the apparatus comprising: a first light source configured to output a sequence of pulses of light, wherein there is a random relationship between the phase of the pulses; a beam splitter having first and second inputs and first and second outputs, said first input being arranged to receive light pulses from said first light source and the second input being arranged to receive said input signal; a differencing circuit adapted to subtract signals obtained from the first and second outputs from each other; and output a value; and a processing circuit adapted to estimate the minimum entropy of said input signal, from the output of the differencing circuit corresponding to a sequence of said light pulses from the first light source.

Abstract: An apparatus for measuring an input signal, the apparatus comprising: a first light source configured to output a sequence of pulses of light, wherein there is a random relationship between the phase of the pulses; a beam splitter having first and second inputs and first and second outputs, said first input being arranged to receive light pulses from said first light source and the second input being arranged to receive said input signal; a differencing circuit adapted to subtract signals obtained from the first and second outputs from each other; and output a value; and a processing circuit adapted to estimate the minimum entropy of said input signal, from the output of the differencing circuit corresponding to a sequence of said light pulses from the first light source.