Squeezed Light Generation by Cooper Pair Recombination in a Superconductor-Semiconductor Structure

Electrically Pumped Squeezed Light via Cooper‑Pair Recombination

Introduction

Squeezed light—optical states with reduced quantum noise in one quadrature—underpins precision metrology, quantum communication, and continuous‑variable quantum computing. Conventional sources rely on nonlinear crystals or optical parametric oscillators, which require bulky pump lasers and careful phase‑matching. A recent pre‑print (arXiv:2611.14622) and its companion Physical Review B article propose a radically different route: using the intrinsic nonlinearity of Cooper‑pair recombination in a superconductor‑semiconductor heterostructure to generate squeezing electrically, without external optical pumping.

How the Mechanism Works

The authors model a thin semiconductor layer sandwiched between two superconducting contacts. When a bias voltage drives electrons across the junction, Cooper pairs can recombine and emit photons directly into the semiconductor’s optical mode. By treating this process with second‑order perturbation theory, they derive an effective Hamiltonian where the photon‑pair creation term is proportional to the square of the superconducting energy gap (Δ) and to the device length (L). The resulting interaction mimics a parametric down‑conversion process, but the nonlinearity originates from the electronic pairing rather than a χ^(2) crystal.

Predicted Squeezing Performance

Using realistic material parameters—Aluminum contacts (Δ≈ 180 µeV), a 10 µm‑long InGaAs waveguide, and a bias just below the critical current—the calculation yields a squeezing parameter r ≈ 0.3, corresponding to about 2.6 dB of noise reduction. This level is on par with early‑stage optical parametric oscillators and comparable to recent integrated silicon‑nitride squeezers. The theory also predicts that squeezing scales linearly with voltage (up to the superconducting critical voltage) and quadratically with Δ, suggesting that higher‑Tc superconductors could push the performance further.

Practical Considerations and Outlook

While the work is purely theoretical, it outlines clear engineering targets: low‑loss waveguides, high‑quality superconducting contacts, and cryogenic operation below the critical temperature. The authors note that device fabrication would leverage existing hybrid superconductor‑semiconductor platforms used for superconducting qubits and single‑photon detectors, potentially accelerating experimental validation. If realized, such electrically pumped squeezers could be integrated directly on photonic chips, eliminating bulky pump lasers and simplifying the deployment of quantum‑enhanced sensors and communication links.

Conclusion

The proposal adds a compelling new avenue to the toolbox of quantum optics, marrying superconductivity with integrated photonics. Although experimental confirmation remains pending, the theoretical analysis suggests that Cooper‑pair recombination could become a viable, compact source of squeezed light, opening pathways for on‑chip quantum technologies that demand low‑noise optical states.