@article{14489,
  abstract     = {Microwave-optics entanglement is a vital component for building hybrid quantum networks. Here, a new mechanism for preparing stationary entanglement between microwave and optical cavity fields in a cavity optomagnomechanical system is proposed. It consists of a magnon mode in a ferrimagnetic crystal that couples directly to a microwave cavity mode via the magnetic dipole interaction and indirectly to an optical cavity through the deformation displacement of the crystal. The mechanical displacement is induced by the magnetostrictive force and coupled to the optical cavity via radiation pressure. Both the opto- and magnomechanical couplings are dispersive. Magnon–phonon entanglement is created via magnomechanical parametric down-conversion, which is further distributed to optical and microwave photons via simultaneous optomechanical beamsplitter interaction and electromagnonic state-swap interaction, yielding stationary microwave-optics entanglement. The microwave-optics entanglement is robust against thermal noise, which will find broad potential applications in quantum networks and quantum information processing with hybrid quantum systems.},
  author       = {Fan, Zhi Yuan and Qiu, Liu and Gröblacher, Simon and Li, Jie},
  issn         = {1863-8899},
  journal      = {Laser and Photonics Reviews},
  number       = {12},
  publisher    = {Wiley},
  title        = {{Microwave-optics entanglement via cavity optomagnomechanics}},
  doi          = {10.1002/lpor.202200866},
  volume       = {17},
  year         = {2023},
}

@phdthesis{13106,
  abstract     = {Quantum entanglement is a key resource in currently developed quantum technologies. Sharing this fragile property between superconducting microwave circuits and optical or atomic systems would enable new functionalities, but this has been hindered by an energy scale mismatch of >104 and the resulting mutually imposed loss and noise. In this work, we created and verified entanglement between microwave and optical fields in a millikelvin environment. Using an optically pulsed superconducting electro-optical device, we show entanglement between propagating microwave and optical fields in the continuous variable domain. This achievement not only paves the way for entanglement between superconducting circuits and telecom wavelength light, but also has wide-ranging implications for hybrid quantum networks in the context of modularization, scaling, sensing, and cross-platform verification.},
  author       = {Sahu, Rishabh and Qiu, Liu and Hease, William J and Arnold, Georg M and Minoguchi, Y. and Rabl, P. and Fink, Johannes M},
  issn         = {1095-9203},
  keywords     = {Multidisciplinary},
  pages        = {718--721},
  publisher    = {American Association for the Advancement of Science},
  title        = {{Entangling microwaves with light}},
  doi          = {10.1126/science.adg3812},
  volume       = {380},
  year         = {2023},
}

@article{13200,
  abstract     = {Recent quantum technologies have established precise quantum control of various microscopic systems using electromagnetic waves. Interfaces based on cryogenic cavity electro-optic systems are particularly promising, due to the direct interaction between microwave and optical fields in the quantum regime. Quantum optical control of superconducting microwave circuits has been precluded so far due to the weak electro-optical coupling as well as quasi-particles induced by the pump laser. Here we report the coherent control of a superconducting microwave cavity using laser pulses in a multimode electro-optical device at millikelvin temperature with near-unity cooperativity. Both the stationary and instantaneous responses of the microwave and optical modes comply with the coherent electro-optical interaction, and reveal only minuscule amount of excess back-action with an unanticipated time delay. Our demonstration enables wide ranges of applications beyond quantum transductions, from squeezing and quantum non-demolition measurements of microwave fields, to entanglement generation and hybrid quantum networks.},
  author       = {Qiu, Liu and Sahu, Rishabh and Hease, William J and Arnold, Georg M and Fink, Johannes M},
  issn         = {2041-1723},
  journal      = {Nature Communications},
  publisher    = {Nature Research},
  title        = {{Coherent optical control of a superconducting microwave cavity via electro-optical dynamical back-action}},
  doi          = {10.1038/s41467-023-39493-3},
  volume       = {14},
  year         = {2023},
}

@article{10924,
  abstract     = {Solid-state microwave systems offer strong interactions for fast quantum logic and sensing but photons at telecom wavelength are the ideal choice for high-density low-loss quantum interconnects. A general-purpose interface that can make use of single photon effects requires < 1 input noise quanta, which has remained elusive due to either low efficiency or pump induced heating. Here we demonstrate coherent electro-optic modulation on nanosecond-timescales with only 0.16+0.02−0.01 microwave input noise photons with a total bidirectional transduction efficiency of 8.7% (or up to 15% with 0.41+0.02−0.02), as required for near-term heralded quantum network protocols. The use of short and high-power optical pump pulses also enables near-unity cooperativity of the electro-optic interaction leading to an internal pure conversion efficiency of up to 99.5%. Together with the low mode occupancy this provides evidence for electro-optic laser cooling and vacuum amplification as predicted a decade ago.},
  author       = {Sahu, Rishabh and Hease, William J and Rueda Sanchez, Alfredo R and Arnold, Georg M and Qiu, Liu and Fink, Johannes M},
  issn         = {20411723},
  journal      = {Nature Communications},
  publisher    = {Springer Nature},
  title        = {{Quantum-enabled operation of a microwave-optical interface}},
  doi          = {10.1038/s41467-022-28924-2},
  volume       = {13},
  year         = {2022},
}

@article{11353,
  abstract     = {Micro- and nanoscale optical or microwave cavities are used in a wide range of classical applications and quantum science experiments, ranging from precision measurements, laser technologies to quantum control of mechanical motion. The dissipative photon loss via absorption, present to some extent in any optical cavity, is known to introduce thermo-optical effects and thereby impose fundamental limits on precision measurements. Here, we theoretically and experimentally reveal that such dissipative photon absorption can result in quantum feedback via in-loop field detection of the absorbed optical field, leading to the intracavity field fluctuations to be squashed or antisquashed. A closed-loop dissipative quantum feedback to the cavity field arises. Strikingly, this modifies the optical cavity susceptibility in coherent response measurements (capable of both increasing or decreasing the bare cavity linewidth) and causes excess noise and correlations in incoherent interferometric optomechanical measurements using a cavity, that is parametrically coupled to a mechanical oscillator. We experimentally observe such unanticipated dissipative dynamics in optomechanical spectroscopy of sideband-cooled optomechanical crystal cavitiess at both cryogenic temperature (approximately 8 K) and ambient conditions. The dissipative feedback introduces effective modifications to the optical cavity linewidth and the optomechanical scattering rate and gives rise to excess imprecision noise in the interferometric quantum measurement of mechanical motion. Such dissipative feedback differs fundamentally from a quantum nondemolition feedback, e.g., optical Kerr squeezing. The dissipative feedback itself always results in an antisqueezed out-of-loop optical field, while it can enhance the coexisting Kerr squeezing under certain conditions. Our result applies to cavity spectroscopy in both optical and superconducting microwave cavities, and equally applies to any dissipative feedback mechanism of different bandwidth inside the cavity. It has wide-ranging implications for future dissipation engineering, such as dissipation enhanced sideband cooling and Kerr squeezing, quantum frequency conversion, and nonreciprocity in photonic systems.},
  author       = {Qiu, Liu and Huang, Guanhao and Shomroni, Itay and Pan, Jiahe and Seidler, Paul and Kippenberg, Tobias J.},
  issn         = {26913399},
  journal      = {PRX Quantum},
  number       = {2},
  publisher    = {American Physical Society},
  title        = {{Dissipative quantum feedback in measurements using a parametrically coupled microcavity}},
  doi          = {10.1103/PRXQuantum.3.020309},
  volume       = {3},
  year         = {2022},
}

@inproceedings{12088,
  abstract     = {We present a quantum-enabled microwave-telecom interface with bidirectional conversion efficiencies up to 15% and added input noise quanta as low as 0.16. Moreover, we observe evidence for electro-optic laser cooling and vacuum amplification.},
  author       = {Sahu, Rishabh and Hease, William J and Rueda Sanchez, Alfredo R and Arnold, Georg M and Qiu, Liu and Fink, Johannes M},
  booktitle    = {Conference on Lasers and Electro-Optics},
  isbn         = {9781557528209},
  location     = {San Jose, CA, United States},
  publisher    = {Optica Publishing Group},
  title        = {{Realizing a quantum-enabled interconnect between microwave and telecom light}},
  doi          = {10.1364/CLEO_QELS.2022.FW4D.4},
  year         = {2022},
}