13 research outputs found
The role of resonance and bandgaps in high transducers
Bandgaps formed in a piezoelectric transducer with large coupling,
, qualitatively modify its electrical response. This regime
in which electrical loading strongly couples forward and backward waves occurs
in thin-film lithium niobate which has recently become available and amenable
to nanopatterning. In this work, we study how resonance and bandgaps modify the
design and performance of transducers and delay lines in thin-film lithium
niobate. These films are an attractive platform for GHz frequency applications
in low-power RF analog signal processing, optomechanics, and quantum devices
due to their high coupling, low loss, excellent optical properties, and
compatibility with superconducting quantum circuits. We demonstrate aluminum
IDTs in this platform for horizontal shear (SH) waves between and
GHz and longitudinal waves between and GHz. For the SH waves, we
measure a piezoelectric coupling coefficient of and dB/mm
propagation losses in delay lines up to mm with a ns delay in air
at room temperature. Reflections from electrical loading when
is large lead to a departure from the impulse response model
widely used to model surface acoustic wave devices. Finite element method
models and an experimental finger-pair sweep are used to characterize the role
of resonance in these transducers, illuminating the physics behind the
anomalously large motional admittances of these small-footprint IDTs.Comment: 9 pages, 8 figure
Engineering phonon leakage in nanomechanical resonators
We propose and experimentally demonstrate a technique for coupling phonons
out of an optomechanical crystal cavity. By designing a perturbation that
breaks a symmetry in the elastic structure, we selectively induce phonon
leakage without affecting the optical properties. It is shown experimentally
via cryogenic measurements that the proposed cavity perturbation causes loss of
phonons into mechanical waves on the surface of silicon, while leaving photon
lifetimes unaffected. This demonstrates that phonon leakage can be engineered
in on-chip optomechanical systems. We experimentally observe large fluctuations
in leakage rates that we attribute to fabrication disorder and verify this
using simulations. Our technique opens the way to engineering more complex
on-chip phonon networks utilizing guided mechanical waves to connect quantum
systems.Comment: 5 pages, 4 figure
Mechanical Purcell Filters for Microwave Quantum Machines
In circuit quantum electrodynamics, measuring the state of a superconducting
qubit introduces a loss channel which can enhance spontaneous emission through
the Purcell effect, thus decreasing qubit lifetime. This decay can be mitigated
by performing the measurement through a Purcell filter which forbids signal
propagation at the qubit transition frequency. If the filter is also
well-matched at the readout cavity frequency, it will protect the qubit from
decoherence channels without sacrificing measurement speed. We propose and
analyze design for a mechanical Purcell filter, which we also fabricate and
characterize at room temperature. The filter is comprised of an array of
nanomechanical resonators in thin-film lithium niobate, connected in a ladder
topology, with series and parallel resonances arranged to produce a bandpass
response. The modest footprint, steep band edges, and absence of cross-talk in
these filters make them a novel and appealing alternative to analogous
electromagnetic versions currently used in microwave quantum machines.Comment: 5 pages, 5 figure
A single-mode phononic wire
Photons and electrons transmit information to form complex systems and
networks. Phonons on the other hand, the quanta of mechanical motion, are often
considered only as carriers of thermal energy. Nonetheless, their flow can also
be molded in fabricated nanoscale circuits. We design and experimentally
demonstrate wires for phonons that transmit information with little loss or
scattering across a chip. By patterning the surface of a silicon chip, we
completely eliminate all but one channel of phonon conduction. We observe the
emergence of low-loss standing waves in millimeter long phononic wires that we
address and cool optically. Coherent transport and strong optical coupling to a
phononic wire enables new phononic technologies to manipulate information and
energy on a chip.Comment: 21 pages, 4+10 figure
Piezoelectric transduction of a wavelength-scale mechanical waveguide
We present a piezoelectric transducer in thin-film lithium niobate that
converts a 1.7 GHz microwave signal to a mechanical wave in a single mode of a
1 micron-wide waveguide. We measure a -12 dB conversion efficiency that is
limited by material loss. The design method we employ is widely applicable to
the transduction of wavelength-scale structures used in emerging phononic
circuits like those at the heart of many optomechanical microwave-to-optical
quantum converters.Comment: 9 pages, 7 figures. First two authors contributed equally to this
wor
Gigahertz phononic integrated circuits on thin-film lithium niobate on sapphire
Acoustic devices play an important role in classical information processing.
The slower speed and lower losses of mechanical waves enable compact and
efficient elements for delaying, filtering, and storing of electric signals at
radio and microwave frequencies. Discovering ways of better controlling the
propagation of phonons on a chip is an important step towards enabling larger
scale phononic circuits and systems. We present a platform, inspired by decades
of advances in integrated photonics, that utilizes the strong piezoelectric
effect in a thin film of lithium niobate on sapphire to excite guided acoustic
waves immune from leakage into the bulk due to the phononic analogue of
index-guiding. We demonstrate an efficient transducer matched to 50 ohm and
guiding within a 1-micron wide mechanical waveguide as key building blocks of
this platform. Putting these components together, we realize acoustic delay
lines, racetrack resonators, and meander line waveguides for sensing
applications. To evaluate the promise of this platform for emerging quantum
technologies, we characterize losses at low temperature and measure quality
factors on the order of 50,000 at 4 kelvin. Finally, we demonstrate phononic
four-wave mixing in these circuits and measure the nonlinear coefficients to
provide estimates of the power needed for relevant parametric processes.Comment: 15 pages,12 figures, the first two authors contributed equall
Room-temperature Mechanical Resonator with a Single Added or Subtracted Phonon
A room-temperature mechanical oscillator undergoes thermal Brownian motion
with an amplitude much larger than the amplitude associated with a single
phonon of excitation. This motion can be read out and manipulated using laser
light using a cavity-optomechanical approach. By performing a strong quantum
measurement, i.e., counting single photons in the sidebands imparted on a
laser, we herald the addition and subtraction of single phonons on the 300K
thermal motional state of a 4GHz mechanical oscillator. To understand the
resulting mechanical state, we implement a tomography scheme and observe highly
non-Gaussian phase-space distributions. Using a maximum likelihood method, we
infer the density matrix of the oscillator and confirm the counter-intuitive
doubling of the mean phonon number resulting from phonon addition and
subtraction.Comment: 13 pages, 9 figure
Efficient bidirectional piezo-optomechanical transduction between microwave and optical frequency
Efficient interconversion of both classical and quantum information between
microwave and optical frequency is an important engineering challenge. The
optomechanical approach with gigahertz-frequency mechanical devices has the
potential to be extremely efficient due to the large optomechanical response of
common materials, and the ability to localize mechanical energy into a
micron-scale volume. However, existing demonstrations suffer from some
combination of low optical quality factor, low electrical-to-mechanical
transduction efficiency, and low optomechanical interaction rate. Here we
demonstrate an on-chip piezo-optomechanical transducer that systematically
addresses all these challenges to achieve nearly three orders of magnitude
improvement in conversion efficiency over previous work. Our modulator
demonstrates acousto-optic modulation with V. We show
bidirectional conversion efficiency of with microwatts
red-detuned optical pump, and with microwatts blue-detuned pump.
Further study of quantum transduction at millikelvin temperatures is required
to understand how the efficiency and added noise are affected by reduced
mechanical dissipation, thermal conductivity, and thermal capacity.Comment: 20 pages, 14 figure
Nanobenders: efficient piezoelectric actuators for widely tunable nanophotonics at CMOS-level voltages
Tuning and reconfiguring nanophotonic components is needed to realize systems
incorporating many components. The electrostatic force can deform a structure
and tune its optical response. Despite the success of electrostatic actuators,
they suffer from trade-offs between tuning voltage, tuning range, and on-chip
area. Piezoelectric actuation could resolve all these challenges. Standard
materials possess piezoelectric coefficients on the order of
, suggesting extremely small on-chip actuation using
potentials on the order of one volt. Here we propose and demonstrate compact
piezoelectric actuators, called nanobenders, that transduce tens of nanometers
per volt. By leveraging the non-uniform electric field from submicron
electrodes, we generate bending of a piezoelectric nanobeam. Combined with a
sliced photonic crystal cavity to sense displacement, we show tuning of an
optical resonance by and between
and ( linewidths) with only .
Finally, we consider other tunable nanophotonic components enabled by
nanobenders.Comment: 24 pages, 5 + 12 figure
Strong dispersive coupling between a mechanical resonator and a fluxonium superconducting qubit
We demonstrate strong dispersive coupling between a fluxonium superconducting
qubit and a 690 megahertz mechanical oscillator, extending the reach of circuit
quantum acousto-dynamics (cQAD) experiments into a new range of frequencies. We
have engineered a qubit-phonon coupling rate of
, and achieved a dispersive interaction that
exceeds the decoherence rates of both systems while the qubit and mechanics are
highly nonresonant (). Leveraging this strong coupling, we
perform phonon number-resolved measurements of the mechanical resonator and
investigate its dissipation and dephasing properties. Our results demonstrate
the potential for fluxonium-based hybrid quantum systems, and a path for
developing new quantum sensing and information processing schemes with phonons
at frequencies below 700 MHz to significantly expand the toolbox of cQAD.Comment: 22 pages, 12 figure