Analog information processing at the quantum limit with a Josephson ring modulator

Understand

Amplifiers are crucial in every experiment carrying out a very sensitive measurement.

• However, they always degrade the information by adding noise.
• Quantum mechanics puts a limit on how small this degradation can be.
• Theoretically, the minimum noise energy added by a phase preserving amplifier to the signal it processes amounts at least to half a photon at the signal frequency.