Alexey K. Feofanov

Quantum-limited directional amplifiers with optomechanics

  1. Daniel Malz,
  2. Lázló D. Tóth,
  3. Nathan R. Bernier,
  4. Alexey K. Feofanov,
  5. Tobias J. Kippenberg,
  6. and Andreas Nunnenkamp
Directional amplifiers are an important resource in quantum information processing, as they protect sensitive quantum systems from excess noise. Here, we propose an implementation of
phase-preserving and phase-sensitive directional amplifiers for microwave signals in an electromechanical setup comprising two microwave cavities and two mechanical resonators. We show that both can reach their respective quantum limits on added noise. In the reverse direction, they emit thermal noise stemming from the mechanical resonators and we discuss how this noise can be suppressed, a crucial aspect for technological applications. The isolation bandwidth in both is of the order of the mechanical linewidth divided by the amplitude gain. We derive the bandwidth and gain-bandwidth product for both and find that the phase-sensitive amplifier has an unlimited gain-bandwidth product. Our study represents an important step toward flexible, on-chip integrated nonreciprocal amplifiers of microwave signals.
arxiv pdf

On-chip microwave-to-optical quantum coherent converter based on a superconducting resonator coupled to an electro-optic microresonator

  1. Clément Javerzac-Galy,
  2. Kirill Plekhanov,
  3. Nathan Bernier,
  4. Laszlo D. Toth,
  5. Alexey K. Feofanov,
  6. and Tobias J. Kippenberg
We propose a device architecture capable of direct quantum electro-optical conversion of microwave to optical photons. The hybrid system consists of a planar superconducting microwave
circuit coupled to an integrated whispering-gallery-mode microresonator made from an electro-optical material. We show that electro-optical (vacuum) coupling rates g0 as large as∼2π(10−100) kHz are achievable with currently available technology, due to the small mode volume of the planar microwave resonator. Operating at millikelvin temperatures, such a converter would enable high-efficiency conversion of microwave to optical photons. We analyze the added noise, and show that maximum conversion efficiency is achieved for a multi-photon cooperativity of unity which can be reached with optical power as low as (1)mW.
arxiv pdf