Microwave-to-optics conversion using a mechanical oscillator in its quantum ground state

Abstract

Conversion between signals in the microwave and optical domains is of great interest both for classical telecommunication, as well as for connecting future superconducting quantum computers into a global quantum network. For quantum applications, the conversion has to be both efficient, as well as operate in a regime of minimal added classical noise. While efficient conversion has been demonstrated with several approaches using mechanical transducers, they have so far all operated with a substantial thermal noise background. Here, we overcome this limitation and demonstrate coherent conversion between GHz microwave signals and the optical telecom band with a thermal background of less than one phonon. We use an electro-opto-mechanical device, that couples surface acoustic waves driven by a resonant microwave signal to an optomechanical crystal featuring a 2.7 GHz mechanical mode. By operating at Millikelvin temperatures, we can initialize the mechanical mode in its quantum groundstate, which allows us to perform the transduction process with less than one quantum of added thermal noise. We further verify the preservation of the coherence of the microwave signal throughout the transduction process. * These authors contributed equally to this work. † s.groeblacher@tudelft.nl arXiv:1812.07588v1 [quant-ph]

Microwave-to-optical conversion using lithium niobate thin-film acoustic resonators

“…3 in Supplementary Material), We estimate the acousto-optic single-photon coupling strength to be g 0 ∼ 1.1 kHz between the 2.17 GHz acoustic mode and the fundamental TE optical mode, which is in good agreement with our theoretical predictions (see Table S1). Another important figure of merit is the photon number conversion efficiency η from the Opto-acoustic S (dB) 21 Acoustic S (dB) 11 Optical microwave frequency to the optical sideband frequency, and it describes the device performance at the single photon level. From the derivation described in Sec.…”

“…Among the many approaches to achieve coherent quantum transduction, electrically-coupled optomechanical systems have emerged as a promising candidate [6]. Experimental progress includes suspended structures such as optical waveguides in microwave cavities [7], membranes in free-space Fabry-Pérot cavities [8][9][10], and nanoscale piezoelectric optomechanical crystals (OMCs) [11][12][13][14][15][16]. While optical waveguides in bulk microwave cavities benefit from the high quality (Q) factors of microwave resonance, the suspended membranes achieve a high photon number conversion efficiency leveraging a triple resonance of microwave, mechanical, and optical fields.…”

“…Microwave-to-mechanical (i.e. electromechanical) coupling to OMCs has been achieved using piezoelectric materials, such as aluminum nitride [14][15][16], gallium arsenide [11,13], and lithium niobate (LN) [12]. However, the demonstrated electromechanical couplings are inefficient due to the mismatch between the mechanical resonant modes to microwaves [12,15,16] or travelling mechanical waves [11,13,14].…”

Electro-optic entanglement source for microwave to telecom quantum state transfer

“…Mechanical generation of microwave-optical entanglement has been proposed [19][20][21][22][23][24][25] but an experimental realization remains challenging. Low frequency mechanical transducers typically suffer from added noise and low bandwidth, while high frequency piezoelectric devices require sophisticated wave matching and new materials, which so far results in low total interaction efficiencies [26][27][28], comparable to magnon-based interfaces [29].…”

A tunable high-Q millimeter wave cavity for hybrid circuit and cavity QED experiments

“…Hybrid systems, which cross-couple these regimes, can harness the strengths of optical systems for communication and microwave systems for quantum information processing, yielding a more powerful toolset for quantum information technology 10 . In particular, the coherent interconversion of microwave and optical photons would enable large quantum networks and robust transfer of quantum information [11][12][13][14][15][16][17][18] .…”