A transmission method includes: in a first period, causing a light source to emit light having a first luminance; and in a second period, causing the light source to transmit an optical signal by causing the light source to alternately emit light having a second luminance and light having a third luminance lower than the second luminance.

A transmission method includes: in a first period, causing a light source to emit light having a first luminance; and in a second period, causing the light source to transmit an optical signal by causing the light source to alternately emit light having a second luminance and light having a third luminance lower than the second luminance.

A quantum communications system may include transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may be configured to co-propagate a first pulse for a quantum state and a second pulse to stabilize the quantum state through the quantum communications channel.

A quantum communications system may include transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may be configured to co-propagate a first pulse for a quantum state and a second pulse to stabilize the quantum state through the quantum communications channel.

A function of detecting an unused path through which actual data is not transmitted in a long-distance redundant network is realized at low cost. In an optical transmission system 20, each of the optical transceivers 21a and 21b that are connected to each other by an optical fiber cable 22 and disposed separately includes a protocol IC unit 35. The protocol IC unit 35 transmits an idle signal A1 with empty data using an optical signal P1 to an unused path of the optical fiber cable 22. At the time of this transmission, the protocol IC unit 35 outputs, to the transmission unit 33, a control signal C1 for performing, at a fixed modulation period, ON/OFF modulation on the optical signal P1 on which the idle signal A1 is superimposed. Also, the protocol IC unit 35 transmits an OAM signal O1 at an OAM period that is a period different from a modulation period, and performs control to turn ON the control signal C1 at the time of this transmission. The protocol IC unit 35 performs control to set the QAM period T2 as a period longer than or equal to a plurality of modulation periods T1. The transmission unit 33 is configured to perform ON/OFF modulation on the optical signal P1 using the control signal C1, and transmits the modulated optical signal P1.

A method for generating a voltage waveform includes providing an optical signal, which comprises one or more sequences of optical pulses, distributing the optical pulses via optical waveguides to a plurality of optical-to-electrical converter units, using the optical-to-electrical converter units to convert the optical pulses into electric driving current pulses, generating voltage pulses by driving Josephson junctions with the electric driving current pulses.

A method for generating a voltage waveform includes providing an optical signal, which comprises one or more sequences of optical pulses, distributing the optical pulses via optical waveguides to a plurality of optical-to-electrical converter units, using the optical-to-electrical converter units to convert the optical pulses into electric driving current pulses, generating voltage pulses by driving Josephson junctions with the electric driving current pulses.

A system for controlling a pulsed laser diode includes a power source configured to supply power to the pulsed laser diode and at least one driving branch between the power source and the pulsed laser diode. The at least one driving branch is configured to control power delivery from the power source to the pulsed laser diode. The at least one driving branch is connected to a cathode of the pulsed laser diode.

A method for providing an electric waveform at a cryogenic temperatures includes providing an optical signal, which comprises an optical waveform, guiding the optical signal into a cryogenic chamber, and converting the optical waveform of the optical signal into an electric waveform inside the cryogenic chamber.

A method for providing an electric waveform at a cryogenic temperatures includes providing an optical signal, which comprises an optical waveform, guiding the optical signal into a cryogenic chamber, and converting the optical waveform of the optical signal into an electric waveform inside the cryogenic chamber.