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October 2005 EEEL Researchers Create Quantum-based Josephson Waveforms Using Optically Generated Pulses |
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Scientists in the Quantum Electrical Metrology Division and the Optoelectronics Division of the Electronics and Electrical Engineering Laboratory have demonstrated a new bias technique that uses optical pulses to drive Josephson junction circuits to generate precision low voltage AC waveforms. The work was funded in part through a competence proposal to use precision AC waveform synthesis to calibrate electronics used to measure the noise from a resistor and consequently determine temperature, namely Johnson noise thermometry. Previously, the Josephson junction circuits were driven directly by a conventional bit-stream generator that produces electrical pulses. By using a modulated laser diode, an Erbium-doped fiber amplifier and a high-speed photodiode, the pulse signal from the bitstream generator is optically isolated from the precision Josephson junction circuits. The removal of the code-generator ground from the measurement system ground eliminates potential ground loops which are detrimental to the precision noise measurement system. Furthermore, by using additional fiber splitters the new optical bias technique enables operation of multiple Josephson junction circuits with only one code generator. The technique may also lead to new methods for generating quantum-based precision waveforms with much higher amplitude which are needed for AC voltage metrology. Scientists:
Contact: Sam Benz (Division 817) 303-497-5258
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