4,897 research outputs found
A handheld high-sensitivity micro-NMR CMOS platform with B-field stabilization for multi-type biological/chemical assays
We report a micro-nuclear magnetic resonance (NMR) system compatible with multi-type biological/chemical lab-on-a-chip assays. Unified in a handheld scale (dimension: 14 x 6 x 11 cm³, weight: 1.4 kg), the system is capable to detect<100 pM of Enterococcus faecalis derived DNA from a 2.5 μL sample. The key components are a portable magnet (0.46 T, 1.25 kg) for nucleus magnetization, a system PCB for I/O interface, an FPGA for system control, a current driver for trimming the magnetic (B) field, and a silicon chip fabricated in 0.18 μm CMOS. The latter, integrated with a current-mode vertical Hall sensor and a low-noise readout circuit, facilitates closed-loop B-field stabilization (2 mT → 0.15 mT), which otherwise fluctuates with temperature or sample displacement. Together with a dynamic-B-field transceiver with a planar coil for micro-NMR assay and thermal control, the system demonstrates: 1) selective biological target pinpointing; 2) protein state analysis; and 3) solvent-polymer dynamics, suitable for healthcare, food and colloidal applications, respectively. Compared to a commercial NMR-assay product (Bruker mq-20), this platform greatly reduces the sample consumption (120x), hardware volume (175x), and weight (96x)
A 65-nm CMOS Temperature-Compensated Mobility-Based Frequency reference for wireless sensor networks
For the first time, a temperature-compensated CMOS frequency reference based on the electron mobility in a MOS transistor is presented. Over the temperature range from -55°C to 125 °C, its frequency spread is less than ±0.5% after a two-point trim and less than ±2.7% after a one-point trim. These results make it suitable for use in Wireless Sensor Network nodes. Fabricated in a baseline 65-nm CMOS process, the 150 kHz frequency reference occupies 0.2 mm2 and draws 42.6 μA from a 1.2-V supply at room temperature.\ud
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An Ultra-Low-Power Oscillator with Temperature and Process Compensation for UHF RFID Transponder
This paper presents a 1.28MHz ultra-low-power oscillator with temperature and process compensation. It is very suitable for clock generation circuits used in ultra-high-frequency (UHF) radio-frequency identification (RFID) transponders. Detailed analysis of the oscillator design, including process and temperature compensation techniques are discussed. The circuit is designed using TSMC 0.18μm standard CMOS process and simulated with Spectre. Simulation results show that, without post-fabrication calibration or off-chip components, less than ±3% frequency variation is obtained from –40 to 85°C in three different process corners. Monte Carlo simulations have also been performed, and demonstrate a 3σ deviation of about 6%. The power for the proposed circuitry is only 1.18µW at 27°C
Manipulating Fock states of a harmonic oscillator while preserving its linearity
We present a new scheme for controlling the quantum state of a harmonic
oscillator by coupling it to an anharmonic multilevel system (MLS) with first
to second excited state transition frequency on-resonance with the oscillator.
In this scheme that we call "ef-resonant", the spurious oscillator Kerr
non-linearity inherited from the MLS is very small, while its Fock states can
still be selectively addressed via an MLS transition at a frequency that
depends on the number of photons. We implement this concept in a circuit-QED
setup with a microwave 3D cavity (the oscillator, with frequency 6.4 GHz and
quality factor QO=2E-6) embedding a frequency tunable transmon qubit (the MLS).
We characterize the system spectroscopically and demonstrate selective
addressing of Fock states and a Kerr non-linearity below 350 Hz. At times much
longer than the transmon coherence times, a non-linear cavity response with
driving power is also observed and explained.Comment: 8 pages, 5 figure
Quantum-to-Classical Transition in Cavity Quantum Electrodynamics
The quantum properties of electromagnetic, mechanical or other harmonic
oscillators can be revealed by investigating their strong coherent coupling to
a single quantum two level system in an approach known as cavity quantum
electrodynamics (QED). At temperatures much lower than the characteristic
energy level spacing the observation of vacuum Rabi oscillations or mode
splittings with one or a few quanta asserts the quantum nature of the
oscillator. Here, we study how the classical response of a cavity QED system
emerges from the quantum one when its thermal occupation -- or effective
temperature -- is raised gradually over 5 orders of magnitude. In this way we
explore in detail the continuous quantum-to-classical crossover and demonstrate
how to extract effective cavity field temperatures from both spectroscopic and
time-resolved vacuum Rabi measurements.Comment: revised version: improved analysis, 4 pages, 4 figures, hi-res
version available at http://qudev.ethz.ch/content/science/PubsPapers.htm
Phase-Coherent Dynamics of a Superconducting Flux Qubit with Capacitive-Bias Readout
We present a systematic study of the phase-coherent dynamics of a
superconducting three-Josephson-junction flux qubit. The qubit state is
detected with the integrated-pulse method, which is a variant of the pulsed
switching DC SQUID method. In this scheme the DC SQUID bias current pulse is
applied via a capacitor instead of a resistor, giving rise to a narrow
band-pass instead of a pure low-pass filter configuration of the
electromagnetic environment. Measuring one and the same qubit with both setups
allows a direct comparison. With the capacitive method about four times faster
switching pulses and an increased visibility are achieved. Furthermore, the
deliberate engineering of the electromagnetic environment, which minimizes the
noise due to the bias circuit, is facilitated. Right at the degeneracy point
the qubit coherence is limited by energy relaxation. We find two main noise
contributions. White noise is limiting the energy relaxation and contributing
to the dephasing far from the degeneracy point. 1/f-noise is the dominant
source of dephasing in the direct vicinity of the optimal point. The influence
of 1/f-noise is also supported by non-random beatings in the Ramsey and spin
echo decay traces. Numeric simulations of a coupled qubit-oscillator system
indicate that these beatings are due to the resonant interaction of the qubit
with at least one point-like fluctuator, coupled especially strongly to the
qubit.Comment: Minor changes. 21 pages, 15 figure
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