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 electrooptical material. We show that by exploiting the large vacuum electric field of the planar microwave resonator, electro-optical (vacuum) coupling rates g0 as large as ∼ 2π O(10 − 100) kHz are achievable with currently available technology -a more than three order of magnitude improvement over prior designs and realizations. 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 quantum coherent conversion efficiency is achieved for a multi-photon cooperativity of unity which can be reached with optical power as low as O(1) mW.The interconversion of microwave and optical signals is of practical relevance in a broad range of electronic applications, from optical and wireless communications to timing. The spectacular advances of the past decade in manipulating the quantum states of the microwave field [1, 2] has increased interest in techniques to convert them to optical fields, since the latter can be propagated via optical fiber at room temperature while preserving their quantum state. In the long term, converting quantum states between microwave and optical photons may enable long distance quantum communication [3,4], and in the near term, it provides a path towards realizing single photon detectors of the microwave field that may find use in quantum science and metrology, radio astronomy and technology alike. For these reasons, hybrid systems for such microwave to optical interfaces have recently attracted significant experimental efforts. Several approaches have been investigated [5,6]: optomechanical and electromechanical devices [7][8][9][10] as well as cold atoms [11] and spin ensembles [12,13]. Indeed, a bi-directional and efficient link has been established recently using a mechanical oscillator coupled to both optical and microwave modes. Alternatively, it has been proposed that the parametric coupling of an LC circuit to an optical cavity via an electro-optical crystal would realize an effective optomechanical-type interaction [14]. Such a system could convert states from the microwave to the optical domain by driving sideband cooling transitions [15][16][17]. Similar to optomechanical systems, the interaction requires large vacuum coupling rates and the resolved-sideband regime [15][16][17] to be efficient as well as a optical cavity decay rate that greatly exceeds the microwave decay rate. Despite interest in the scheme, to date, it has not been realized. Previous demonstrations attained vacuum coupling rates of ∼ 2π O(1 − 10)Hz insufficient for an efficient transfer. In addition, several previous schemes operated with a microwave dissipation that was larger than the optical one, preventing efficient transfer...

We present quantum yield measurements of single layer WSe2 (1L-WSe2) integrated with high-Q (Q > 106) optical microdisk cavities, using an efficient (η > 90%) near-field coupling scheme based on a tapered optical fiber. Coupling of the excitonic emission is achieved by placing 1L-WSe2 in the evanescent cavity field. This preserves the microresonator high intrinsic quality factor (Q > 106) below the bandgap of 1L-WSe2. The cavity quantum yield is QYc ≈ 10–3, consistent with operation in the broad emitter regime (i.e., the emission lifetime of 1L-WSe2 is significantly shorter than the bare cavity decay time). This scheme can serve as a precise measurement tool for the excitonic emission of layered materials into cavity modes, for both in plane and out of plane excitation.

Efficient deterministic algorithms are proposed with logarithmic step complexities for the generation of entangled GHZN and WN states useful for quantum networks, and an implementation on the IBM quantum computer up to N=16 is demonstrated. Improved quality is then investigated using full quantum tomography for low‐N GHZ and W states. This is completed by parity oscillations and histogram distance for large‐N GHZ and W states, respectively. Robust states are built with about twice the number of quantum bits which were previously achieved.

The unavailability of highly transparent materials in the mid-infrared has been the main limitation in the development of ultra-sensitive molecular sensors or cavity-based spectroscopy applications. Whispering gallery mode microresonators have attained ultra-high-quality (Q) factor resonances in the near-infrared and visible. Here we report ultra-high Q factors in the mid-infrared using polished alkaline earth metal fluoride crystals. Using an uncoated chalcogenide tapered fibre as a high-ideality coupler in the mid-infrared, we study via cavity ringdown technique the losses of BaF2, CaF2, MgF2 and SrF2 microresonators. We show that MgF2 is limited by multiphonon absorption by studying the temperature dependence of the Q factor. In contrast, in SrF2 and BaF2 the lower multiphonon absorption leads to ultra-high Q factors at 4.5 μm. These values correspond to an optical finesse of , the highest value achieved for any type of mid-infrared resonator to date.

Monolayer transition-metal dichalcogenides with direct bandgaps are emerging candidates for optoelectronic devices, such as photodetectors, light-emitting diodes, and electro-optic modulators. Here we report a low-loss integrated platform incorporating molybdenum ditelluride monolayers with silicon nitride photonic microresonators. We achieve microresonator quality factors >3 × 106 in the telecommunication O- to E-bands. This paves the way for low-loss, hybrid photonic integrated circuits with layered semiconductors, not requiring heterogeneous wafer bonding.