Nano-acoustic resonator with ultralong phonon lifetime

The energy damping time in a mechanical resonator is critical to many precision metrology applications, such as timekeeping and force measurements. We present measurements of the phonon lifetime of a microwave-frequency, nanoscale silicon acoustic cavity incorporating a phononic bandgap acoustic shield. Using pulsed laser light to excite a colocalized optical mode of the cavity, we measured the internal acoustic modes with single-phonon sensitivity down to millikelvin temperatures, yielding a phonon lifetime of up to τ_(ph,0) ≈ 1.5 seconds (quality factor Q = 5 × 10¹⁰) and a coherence time of τ_(coh,0) ≈ 130 microseconds for bandgap-shielded cavities. These acoustically engineered nanoscale structures provide a window into the material origins of quantum noise and have potential applications ranging from tests of various collapse models of quantum mechanics to miniature quantum memory elements in hybrid superconducting quantum circuits

Nano-acoustic resonator with ultralong phonon lifetime

The energy damping time in a mechanical resonator is critical to many precision metrology applications, such as timekeeping and force measurements. We present measurements of the phonon lifetime of a microwave-frequency, nanoscale silicon acoustic cavity incorporating a phononic bandgap acoustic shield. Using pulsed laser light to excite a colocalized optical mode of the cavity, we measured the internal acoustic modes with single-phonon sensitivity down to millikelvin temperatures, yielding a phonon lifetime of up to τ_(ph,0) ≈ 1.5 seconds (quality factor Q = 5 × 10¹⁰) and a coherence time of τ_(coh,0) ≈ 130 microseconds for bandgap-shielded cavities. These acoustically engineered nanoscale structures provide a window into the material origins of quantum noise and have potential applications ranging from tests of various collapse models of quantum mechanics to miniature quantum memory elements in hybrid superconducting quantum circuits

Phononic bandgap nano-acoustic cavity with ultralong phonon lifetime

We present measurements at millikelvin temperatures of the microwave-frequency acoustic properties of a crystalline silicon nanobeam cavity incorporating a phononic bandgap clamping structure for acoustic confinement. Utilizing pulsed laser light to excite a co-localized optical mode of the nanobeam cavity, we measure the dynamics of cavity acoustic modes with single-phonon sensitivity. Energy ringdown measurements for the fundamental 5 GHz acoustic mode of the cavity shows an exponential increase in phonon lifetime versus number of periods in the phononic bandgap shield, increasing up to τ_(ph,0) ≈ 1.5~seconds. This ultralong lifetime, corresponding to an effective phonon propagation length of several kilometers, is found to be consistent with damping from non-resonant two-level system defects on the surface of the silicon device. Potential applications of these ultra-coherent nanoscale mechanical resonators range from tests of various collapse models of quantum mechanics to miniature quantum memory elements in hybrid superconducting quantum circuits

Dynamic Hosts for High-Performance Li–S Batteries Studied by Cryogenic Transmission Electron Microscopy and in Situ X‑ray Diffraction

Developing a high-performance sulfur host is central to the commercialization and general development of lithium–sulfur batteries. Here, for the first time, we propose the concept of dynamic hosts for lithium–sulfur batteries and elucidate the mechanism through which TiS₂ acts in such a fashion, using in situ X-ray diffraction and cryogenic scanning transmission electron microscopy (cryo-STEM). A TiS₂–S composite electrode delivered a reversible capacity of 1120 mAh g^–1 at 0.3 C after 200 cycles with a capacity retention of 97.0% and capacities of 886 and 613 mAh g^–1 at 1.0 C up to 200 and 1000 cycles, respectively. Our results indicate that it is Li_<i>x</i>TiS₂ (0 < <i>x</i> ≤ 1), rather than TiS₂, that effectively traps polysulfides and catalytically decomposes Li₂S