arXiv subjects

Mads B. Kristensen

Publications and source records attributed to Mads B. Kristensen.

3 recordsLinked to original sources

arXiv2026

Optomechanical crystal in light-resilient quantum ground state

Interaction between light and high-frequency sound is a key area in integrated photonics, quantum and nonlinear optics, and quantum science. However, typical suspended optomechanical structures suffer from poor thermal anchoring, making them susceptible to thermal noise arising from optical absorption. Here, we demonstrate a chip-scale, release-free silicon optomechanical crystal cavity operating cryogenically with improved resilience to laser light. Relative to a suspended design, we observe 18 dB suppression of the thermo-optic effect, and the device also sustains near-unity phonon occupation at 35 dB higher intracavity optical energy in continuous-wave operation. Non-exponential decay dynamics from an as yet unidentified thermal process limit transfer of this performance to pulsed operation. Resolving this channel would open a clear path to near-term quantum protocols, such as microwave-to-optical quantum transduction. More broadly, the release-free architecture offers a novel platform for studying thermal noise dynamics with results relevant across silicon optomechanical platforms.

quant-ph↗

arXiv2026

Release-free electro-optomechanical crystal modulator

Electro-optic modulation is central to classical optical communications and emerging quantum technologies. High-confinement optomechanical crystal modulators enable microwave-optical transduction through strong optomechanical interactions and offer a promising interface between superconducting qubits and optical fibers. However, their performance is limited by thermal noise from optical absorption. Release-free optomechanical crystals provide improved thermal anchoring but have not yet been integrated into a microwave-optical transducer. Here, we demonstrate a release-free electro-optomechanical transducer combining strong optomechanical interactions in silicon with the efficient piezoelectricity of lithium niobate via micro-transfer printing. We observe electro- and optomechanical coupling rates compatible with quantum-level operation when co-integrated with a superconducting microwave circuit. This advance moves release-free electro-optomechanical devices toward practical microwave-optical interfaces.

quant-ph↗

arXiv2024

A soft-clamped topological waveguide for phonons

Topological insulators were originally discovered for electron waves in condensed matter systems. Recently this concept has been transferred to bosonic systems such as photons and phonons, which propagate in materials patterned with artificial lattices that emulate spin-Hall physics. This work has been motivated, in part, by the prospect of topologically protected transport along edge channels in on-chip circuits. Importantly, even in principle, topology protects propagation against backscattering, but not against loss, which has remained limited to the dB/cm-level for phonon waveguides, be they topological or not. Here, we combine advanced dissipation engineering, in particular the recently introduced method of soft-clamping, with the concept of a valley-Hall topological insulator for phonons. This enables on-chip phononic waveguides with propagation losses of 3 dB/km at room temperature, orders of magnitude below any previous chip-scale devices. For the first time, the low losses also allow us to accurately quantify backscattering protection in a topological phonon waveguide, using high-resolution ultrasound spectroscopy. We infer that phonons follow a sharp, 120 degree-bend with a 99.99%-probability instead of being scattered back, and less than one phonon in a million is lost. The extraordinary combination of features of this novel platform suggest applications in classical and quantum signal routing, processing, and storage.

cond-mat.mes-hall↗