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

Abstract

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...

Efficient microwave to optical photon conversion: an electro-optical realization

“…Assuming a realistic resonator thickness of 50 μm, together with the closing of any air gaps deteriorating g, can improve the cooperativity additionally by 2 to 3 orders of magnitude. Recently, theoretical studies showed additional ways to increase g [38,39]. Putting these optimizations together, G 0 ≈ 1 within an overcoupled regime can be achieved in a realistic scenario, ready to realize quantum state transfer [40].…”

Monolithic ultra-high-Q lithium niobate microring resonator

“…The ultralow loss, high optical confinement and tight bending radius combined with the ability to integrate microwave electrodes [7] will bring electro-optic [2,7] nonlinear optical [4] systems into a new design parameter space that has been inaccessible so far. This could enable a wide range of applications including those in ultralow loss quantum photonics [9] ,coherent microwave to optical conversion [10,11] and active topological photonics [12]. We emphasize that the LN device layer sits atop a standard silicon handle wafer and therefore our platform can also be integrated with many existing photonic technologies.…”

Photonic integrated circuits with bound states in the continuum

“…Figure 4g shows the temporal response of the MZI electro-optic modulator, indicating the modulation speed can be higher than 100 Mbps (see Supplementary Information). Such devices can be used for manipulating the frequency properties of photons on a chip, and the electro-optic interaction can be enhanced further in high-Q microcavities, which is promising for achieving the microwave-to-optical frequency conversion 32 .…”