Phase sensitive gain

Testing a parametric amplifier. The temperature is 0.04K (well below the quantum limit of the frequency range of interest). The amplifier is made of a superconductive niobium coplanar waveguide cavity whose center conductor is made of a chain of 100 SQUIDs (Superconducting Quantum Interference Device). The device is pumped @ 12.25 GHz to achive phase sensitive gain at 6.125 GHz.

This video demonstrates the phase sensitivity of such an amplifier. The noise spectrum is analyzed with an I/Q analyzer as the phase of the pump signal is tuned. In the first part of the video the pump signal is slightly detuned from the observation frequency and the amplified thermal and quantum noise can be seen to move from one quadrature to another. In the second part the phase is slowly hand adjusted. The pump is also briefly switched off to see the base noise floor determined by the cryogenic LNA stage.

This measurement is related to attempts to study quantum noise and the dynamical casimir effect in superconductive circuits. The internal losses of this sample appear to be too high for the intended purpose though.

Category:

Science & Technology

Tags:

• phase
• sensitive
• parametric
• amplifier