Displacement Readout Research Articles

Simultaneous identification of viruses and viral variants with programmable DNA nanobait

Respiratory infections are the major cause of death from infectious disease worldwide. Multiplexed diagnostic approaches are essential as many respiratory viruses have indistinguishable symptoms. We created self-assembled DNA nanobait that can simultaneously identify multiple short RNA targets. The nanobait approach relies on specific target selection via toehold-mediated strand displacement and rapid readout via nanopore sensing. Here we show that this platform can concurrently identify several common respiratory viruses, detecting a panel of short targets of viral nucleic acids from multiple viruses. Our nanobait can be easily reprogrammed to discriminate viral variants with single-nucleotide resolution, as we demonstrated for several key SARS-CoV-2 variants. Last, we show that the nanobait discriminates between samples extracted from oropharyngeal swabs from negative- and positive-SARS-CoV-2 patients without preamplification. Our system allows for the multiplexed identification of native RNA molecules, providing a new scalable approach for the diagnostics of multiple respiratory viruses in a single assay.

Compact Michelson Interferometers with Subpicometer Sensitivity

The network of interferometric gravitational-wave observatories has successfully detected tens of astrophysical signals since 2015. In this paper, we experimentally investigate compact sensors that have the potential to improve the sensitivity of gravitational-wave detectors to intermediate-mass black holes. We use only commercial components, such as sensing heads and lasers, to assemble the setup and demonstrate its subpicometer precision. The setup consists of a pair of Michelson interferferometers that use deep frequency modulation techniques to obtain a linear, relative displacement readout over multiple interference fringes. We implement a laser-frequency stabilisation scheme to achieve a sensitivity of 0.3\,$\text{pm} / \sqrt{\text{Hz}}$ above 0.1\,Hz. The device has also the potential to improve other experiments, such as torsion balances and commercial seismometers.

Parallel DNA circuits by autocatalytic strand displacement and nanopore readout.

DNA nanotechnology provides a unique opportunity for molecular computation, with strand displacement reactions enabling controllable reorganization of nanostructures. Additional DNA strand exchange strategies with high selectivity for input will enable novel complex systems including biosensing applications. Herein, we propose an autocatalytic strand displacement (ACSD) circuit: initiated by DNA breathing and accelerated by a seesaw catalytic reaction, ACSD ensures that only the correct base sequence starts the catalytic cycle. Analogous to an electronic circuit with a variable resistor, two ACSD reactions with different rates are connected in parallel to mimic a parallel circuit containing branches with different resistances. Finally, we introduce a multiplexed nanopore sensing platform to report the output results of a parallel path selection system at the single-molecule level. By combining the ACSD strategy with fast and sensitive single-molecule nanopore readout, a new generation of DNA-based computing tools is established.

Laser noise control in the optoacoustical gravitational antenna

It is shown that the metric sensitivity theory of the OGRAN project contains description of the Fabry-Perot cavity displacement readout scheme proposed by Braginsky. In theories a quality factor defines laser noise. As an alternative, two phenomenological intrinsic controlled parameters of laser noise are proposed to analyze readout resolution: spectral densities of frequency deviations and power random modulation P(t) = P 0[1 + £(t)]. The formula for vibration noise is derived. The new theory of instrumental sensitivity is applied to explain the effect of readout noise rise while increasing digitization time. To reduce the readout threshold signal from real value of 2 · 10−15 cm/Hz1/2 to required value of 3 · 10−16 cm/Hz1/2 there are proposed actions: 1) to limit temperature drift difference between laser and bar cavity frequencies by value of 250 Hz; 2) to suppress by circuitry means vibration disturbance voltage at the discriminator output while increasing by 20 dB width of feedback frequency range and feedback gain in this range.

Gated Conditional Displacement Readout of Superconducting Qubits.

We have realized a new interaction between superconducting qubits and a readout cavity that results in the displacement of a coherent state in the cavity, conditioned on the state of the qubit. This conditional state, when it reaches the cavity-following, phase-sensitive amplifier, matches its measured observable, namely, the in phase quadrature. In a setup where several qubits are coupled to the same readout resonator, we show it is possible to measure the state of a target qubit with minimal dephasing of the other qubits. Our results suggest novel directions for faster readout of superconducting qubits and implementations of bosonic quantum error-correcting codes.

Calibrating the system dynamics of LISA Pathfinder

LISA Pathfinder (LPF) was a European Space Agency mission with the aim to test key technologies for future space-borne gravitational-wave observatories like LISA. The main scientific goal of LPF was to demonstrate measurements of differential acceleration between free-falling test masses at the sub-femto-g level, and to understand the residual acceleration in terms of a physical model of stray forces, and displacement readout noise. A key step toward reaching the LPF goals was the correct calibration of the dynamics of LPF, which was a three-body system composed by two test-masses enclosed in a single spacecraft, and subject to control laws for system stability. In this work, we report on the calibration procedures adopted to calculate the residual differential stray force per unit mass acting on the two test-masses in their nominal positions. The physical parameters of the adopted dynamical model are presented, together with their role on LPF performance. The analysis and results of these experiments show that the dynamics of the system was accurately modeled and the dynamical parameters were stationary throughout the mission. Finally, the impact and importance of calibrating system dynamics for future space-based gravitational wave observatories is discussed.

Nonlinear cavity optomechanics with nanomechanical thermal fluctuations

Although the interaction between light and motion in cavity optomechanical systems is inherently nonlinear, experimental demonstrations to date have allowed a linearized description in all except highly driven cases. Here, we demonstrate a nanoscale optomechanical system in which the interaction between light and motion is so large (single-photon cooperativity C0≈103) that thermal motion induces optical frequency fluctuations larger than the intrinsic optical linewidth. The system thereby operates in a fully nonlinear regime, which pronouncedly impacts the optical response, displacement measurement and radiation pressure backaction. Specifically, we measure an apparent optical linewidth that is dominated by thermo-mechanically induced frequency fluctuations over a wide temperature range, and show that in this regime thermal displacement measurements cannot be described by conventional analytical models. We perform a proof-of-concept demonstration of exploiting the nonlinearity to conduct sensitive quadratic readout of nanomechanical displacement. Finally, we explore how backaction in this regime affects the mechanical fluctuation spectra.

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results.

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1 fm s^{-2}/sqrt[Hz], or (0.54±0.01)×10^{-15} g/sqrt[Hz], with g the standard gravity, for frequencies between 0.7 and 20mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3) fm/sqrt[Hz], about 2 orders of magnitude better than requirements. At f≤0.5 mHz we observe a low-frequency tail that stays below 12 fm s^{-2}/sqrt[Hz] down to 0.1mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

Near-Field Integration of a SiN Nanobeam and aSiO2Microcavity for Heisenberg-Limited Displacement Sensing

Placing a nanomechanical object in the evanescent near-field of a high-$Q$ optical microcavity gives access to strong gradient forces and quantum-noise-limited displacement readout, offering an attractive platform for precision sensing technology and basic quantum optics research. Robustly implementing this platform is challenging, however, as it requires separating optically smooth surfaces by $\lesssim\lambda/10$. Here we describe a fully-integrated evanescent opto-nanomechanical transducer based on a high-stress Si$_3$N$_4$ nanobeam monolithically suspended above a SiO$_2$ microdisk cavity. Employing a novel vertical integration technique based on planarized sacrificial layers, we achieve beam-disk gaps as little as 25 nm while maintaining mechanical $Q\times f>10^{12}$ Hz and intrinsic optical $Q\sim10^7$. The combined low loss, small gap, and parallel-plane geometry result in exceptionally efficient transduction, characterizing by radio-frequency flexural modes with vacuum optomechanical coupling rates of 100 kHz, single-photon cooperativities in excess of unity, and zero-point frequency (displacement) noise amplitudes of 10 kHz (fm)/$\surd$Hz. In conjunction with the high power handling capacity of SiO$_2$ and low extraneous substrate noise, the transducer operates particularly well as a sensor. Deploying it in a 4 K cryostat, we recently demonstrated a displacement imprecision 40 dB below that at the standard quantum limit (SQL) with an imprecision-back-action product $<5\cdot\hbar$. In this report we provide a comprehensive description of device design, fabrication, and characterization, with an emphasis on extending Heisenberg-limited readout to room temperature. Towards this end, we describe a room temperature experiment in which a displacement imprecision 30 dB below that at the SQL and an imprecision-back-action product $<75\cdot\hbar$ is achieved.

Optical Cavity Interrogation for MEMS Accelerometers

MEMS accelerometers utilizing electrostatic, piezoelectric, and magnetic proof mass displacement readout approaches have achieved success in both commercial- and defense-related applications. However, there is a desire for improved acceleration resolution suitable for navigation-grade applications. Optical readout of mechanical displacements has demonstrated high levels of resolution in macro-scale applications including precision movement and placement systems. In addition, optical techniques are common in high performance inertial sensors such as fiber optic gyros and ring laser gyros. Incorporating optical readout approaches into MEMS acceleration devices may yield sufficient resolution to achieve navigation-grade performance. Therefore, the U.S. Army AMRDEC is developing MEMS accelerometers based on optical cavity resonance readout. In the device, an optical cavity is formed between a MEMS proof mass and a reference reflector. A tunable laser excites the cavity on the edge of its resonance peak. Small displacements of the cavity from its rest position are detected by frequency shifts of the resonance, leading to high-resolution proof mass displacement detection and therefore high acceleration resolutions. This paper will present modeling associated with the design concept, as well predictions of device geometries and performance with the goal of achieving less than 1 micro-g bias instability and a velocity random walk of better than 0.2 micro-g/rt.Hz.

Indium phosphide-based monolithically integrated PIN waveguide photodiode readout for resonant cantilever sensors

An integrated photodiode displacement readout scheme for a microelectromechanical cantilever waveguide resonator sensing platform is presented. III-V semiconductors are used to enable the monolithic integration of passive waveguides with active optical components. This work builds upon previously demonstrated results by measuring the displacement of cantilever waveguide resonators with on-chip waveguide PIN photodiodes. The on-chip integration of the readout provides an additional 70% improvement in mass sensitivity compared to off-chip photodetector designs due to measurement stability and minimized coupling loss. In addition to increased measurement stability, reduced packaging complexity is achieved due to the simplicity of the readout design. We have fabricated cantilever waveguides with integrated photodetectors and experimentally characterized these cantilever sensors with monolithically integrated PIN photodiodes.

Prototype of a Small Low Noise Absolute Displacement Sensor

Inertial seismic sensors typically have a velocity readout, to offer a large dynamic range in a large frequency range. However, in some precision engineering applications, it can be preferable to have access to the displacement. An example is the so-called sky-hook spring strategy used for active vibration isolation. In this paper, we present a prototype of small inertial sensor with a displacement readout. It is based on a commercial low cost geophone, which has been modified to measure the displacement with a capacitive sensor. It results in a compact sensor with a resolution which is a factor 10 better than the commercial geophone, but a limited range of amplitudes. This paper finished with an attempt to extend the bandwidth of the sensor at low frequency.

Verification of polarising optics for the LISA optical bench

The Laser Interferometer Space Antenna (LISA) is a space-based interferometric gravitational wave detector. In the current baseline design for the optical bench, the use of polarising optics is foreseen to separate optical beams. Therefore it is important to investigate the influence of polarising components on the interferometer sensitivity and validate that the required picometre stability in the low-frequency band (1 mHz - 1 Hz) is achievable. This paper discusses the design of the experiment and the implemented stabilisation loops. A displacement readout fulfilling the requirement in the whole frequency band is presented. Alternatively, we demonstrate improvement of the noise performance by implementing various algorithms in data post-processing, which leads to an additional robustness for the LISA mission.

A high-resolution microchip optomechanical accelerometer

The monitoring of acceleration is essential for a variety of applications ranging from inertial navigation to consumer electronics1,2. Typical accelerometer operation involves the sensitive displacement measurement of a flexibly mounted test mass, which can be realized using capacitive3,4, piezo-electric5, tunnel-current6,7 or optical8,9,10,11 methods. Although optical detection provides superior displacement resolution8, resilience to electromagnetic interference and long-range readout7, current optical accelerometers either do not allow for chip-scale integration or utilize relatively bulky test mass sensors of low bandwidth8,9,10. Here, we demonstrate an optomechanical accelerometer that makes use of ultrasensitive displacement readout using a photonic-crystal nanocavity12 monolithically integrated with a nanotethered test mass of high mechanical Q-factor13. This device achieves an acceleration resolution of 10 µg Hz−1/2 with submilliwatt optical power, bandwidth greater than 20 kHz and a dynamic range of greater than 40 dB. Moreover, the nanogram test masses used here allow for strong optomechanical backaction14,15,16,17, setting the stage for a new class of motional sensors.

Subtraction of test mass angular noise in the LISA technology package interferometer

When the position of a test mass in one dimension is measured with picometer accuracy, angular alignment jitter inevitably couples noise into the measurement. We present recent sensitivity measurements of the LISA technology package interferometer with articulated mirrors as test masses, actuated by piezo-electric transducers. The required longitudinal displacement resolution of 9 pm\(/\sqrt{\text{Hz}}\) above 3 mHz has been demonstrated with an angular noise that corresponds to the expected for on-orbit operation. The excess noise contribution of this test mass jitter onto the sensitive displacement readout was completely subtracted by fitting the angular interferometric data streams to the longitudinal displacement measurement. Thus, this cross-coupling constitutes no limitation to the required performance of the LISA technology package interferometry.

GaAs/AlGaAs self-sensing cantilevers for low temperature scanning probe microscopy

We have fabricated scanning probe microscope cantilevers with dimensions 65×11.4×0.25 μm3 and 3×2×0.129 μm3 from GaAs/Al0.3Ga0.7As heterostructures containing two-dimensional electron gases. Deflection is measured by an integrated field-effect transistor (FET) that senses strain via the piezoelectric effect and provides a low noise, low power displacement readout. We present images of a 200 nm mica grating taken with the large cantilever having a deflection (force) noise 10 Å/√Hz (19 pN/√Hz) at T=2.2 K. The small cantilever has a resonant frequency of 11 MHz, a FET gate charge noise of 0.001 e/√Hz, and is projected to have a deflection (force) noise of 0.002 Å/√Hz (1 pN/√Hz) at T=4.2 K.

New technologies for monitoring the precision alignment of large detector systems

Two classes of inexpensive systems are described for performing dynamic, high-resolution measurements of the mechanical alignment between components of a large collider detector. One is a three-opint optical system based on video cameras and simple frame processing, while the other is a multipoint stretched wire with three-dimensional displacement readout. Test results are presented for both types of devices, and an application is outlined for a large muon system.

Gradiometry coexperiments to the gravity probe B and step missions

The Gravity Probe B spacecraft, designed to test predictions of general relativity, will fly in the mid 1990's. It will carry four electrostatically suspended gyroscopes in a cryogenic environment and will have a drag-free control system to minimize disturbances on the gyroscopes. The Stanford Test of Equivalence Principle (STEP) spacecraft, to fly later, will carry a set of test masses under very similar conditions. This paper explores the possibility of using differential measurements of the GP-B gyroscope suspension forces and the STEP test mass displacement readout to form single-axis gravity gradiometers. We show that the noise in the suspension systems is sufficiently small in the relevant frequency range, and that enough information is collected to compensate for the spacecrafts' attitude motion. Finally, using Breakwell's “flat-earth” approximation, we compare these experiments to other geodesy experiments and predict the contribution they can make to the knowledge of the Earth's geopotential.