Quantum frequency conversion

TLDR

Squeezed light has been demonstrated in many experiments, but its use in spectroscopy is limited by fixed‑frequency sources that lack tunability. The paper proposes a scheme to generate frequency‑tunable squeezed light. The method uses sum‑frequency generation, mixing a signal beam at ω₁ with a pump at ω₂ to produce a beam at ω₃ = ω₁ + ω₂. The authors show that the light’s quantum state remains unchanged while its frequency can be altered.

Abstract

Many demonstrations of the generation and application of squeezed light have recently been made. Progress in its application to spectroscopy, 1 however, has been hampered by the lack of tunable sources of squeezed light. Present sources generate squeezing around a fixed frequency, whereas for spectroscopic applications, tunability is desirable. Here, I propose a scheme by which frequency-tunable squeezed light can be generated. I show that it is possible to change a light beam's frequency without affecting its quantum state. Consider the sum frequency process wherein a beam at ω 1 is mixed with a pump beam at ω 2 to generate the sum ω 3 = ω 1 + ω 2 .