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Lock-in amplifier

About: Lock-in amplifier is a research topic. Over the lifetime, 521 publications have been published within this topic receiving 4455 citations.


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Journal ArticleDOI
TL;DR: In this paper, the basic principles behind the operation of a lock-in amplifier are described, with particular emphasis on looking at the frequency components of the signal present at the various stages of the lockin during a typical measurement.
Abstract: The basic principles behind the operation of a lock‐in amplifier are described. Particular emphasis is placed on looking at the frequency components of the signal present at the various stages of the lock‐in during a typical measurement. The description presented here has been used successfully to explain lock‐in operation to upper‐level laboratory students at Oberlin College.

243 citations

Journal ArticleDOI
05 May 2011-Nature
TL;DR: In this article, a quantum analogue to the classical lock-in amplifier was proposed to increase the sensitivity of a single-spin probe to external magnetic fields. But the quantum lock-ins were not applied to the measurement of parity nonconservation.
Abstract: Quantum metrology uses tools from quantum information science to improve measurement signal-to-noise ratios. The challenge is to increase sensitivity while reducing susceptibility to noise, tasks that are often in conflict. Lock-in measurement is a detection scheme designed to overcome this difficulty by spectrally separating signal from noise. Here we report on the implementation of a quantum analogue to the classical lock-in amplifier. All the lock-in operations--modulation, detection and mixing--are performed through the application of non-commuting quantum operators to the electronic spin state of a single, trapped Sr(+) ion. We significantly increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. Using this technique, we measure frequency shifts with a sensitivity of 0.42 Hz Hz(-1/2) (corresponding to a magnetic field measurement sensitivity of 15 pT Hz(-1/2)), obtaining an uncertainty of less than 10 mHz (350 fT) after 3,720 seconds of averaging. These sensitivities are limited by quantum projection noise and improve on other single-spin probe technologies by two orders of magnitude. Our reported sensitivity is sufficient for the measurement of parity non-conservation, as well as the detection of the magnetic field of a single electronic spin one micrometre from an ion detector with nanometre resolution. As a first application, we perform light shift spectroscopy of a narrow optical quadrupole transition. Finally, we emphasize that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor.

152 citations

01 May 2011
TL;DR: The implementation of a quantum analogue to the classical lock-in amplifier is reported on, which significantly increases its sensitivity to external fields while extending phase coherence by three orders of magnitude and can potentially enhance the sensitivity of any quantum sensor.
Abstract: Quantum metrology uses tools from quantum information science to improve measurement signal-to-noise ratios. The challenge is to increase sensitivity while reducing susceptibility to noise, tasks that are often in conflict. Lock-in measurement is a detection scheme designed to overcome this difficulty by spectrally separating signal from noise. Here we report on the implementation of a quantum analogue to the classical lock-in amplifier. All the lock-in operations--modulation, detection and mixing--are performed through the application of non-commuting quantum operators to the electronic spin state of a single, trapped Sr(+) ion. We significantly increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. Using this technique, we measure frequency shifts with a sensitivity of 0.42 Hz Hz(-1/2) (corresponding to a magnetic field measurement sensitivity of 15 pT Hz(-1/2)), obtaining an uncertainty of less than 10 mHz (350 fT) after 3,720 seconds of averaging. These sensitivities are limited by quantum projection noise and improve on other single-spin probe technologies by two orders of magnitude. Our reported sensitivity is sufficient for the measurement of parity non-conservation, as well as the detection of the magnetic field of a single electronic spin one micrometre from an ion detector with nanometre resolution. As a first application, we perform light shift spectroscopy of a narrow optical quadrupole transition. Finally, we emphasize that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor.

123 citations

Journal ArticleDOI
TL;DR: A novel digital lock-in detection technique for simultaneously measuring the amplitude and phase of multiple amplitude-modulated signals and can be performed as a simple matrix multiplication, which considerably reduces the computation time.
Abstract: We introduce a novel digital lock-in detection technique for simultaneously measuring the amplitude and phase of multiple amplitude-modulated signals. Using particular modulation and sampling constraints and averaging filters, we achieve optimal noise reduction and discrimination between sources of different modulation frequencies. Furthermore, it is shown that the digital lock-in technique can be performed as a simple matrix multiplication, which considerably reduces the computation time. The digital lock-in algorithm is described and analyzed under certain sampling and modulation conditions, and results are shown for both numerical and experimental data.

118 citations

Journal ArticleDOI
TL;DR: A high-performance digital lock-in amplifier implemented in a low-cost digital signal processor (DSP) board is described, capable of measuring simultaneously multiple frequencies that change in time as frequency sweeps (chirps).
Abstract: A high-performance digital lock-in amplifier implemented in a low-cost digital signal processor (DSP) board is described. This lock in is capable of measuring simultaneously multiple frequencies that change in time as frequency sweeps (chirps). The used 32‐bit DSP has enough computing power to generate N=3 simultaneous reference signals and accurately measure the N=3 responses, operating as three lock ins connected in parallel to a linear system. The lock in stores the measured values in memory until they are downloaded to the a personal computer (PC). The lock in works in stand-alone mode and can be programmed and configured through the PC serial port. Downsampling and multiple filter stages were used in order to obtain a sharp roll off and a long time constant in the filters. This makes measurements possible in presence of high-noise levels. Before each measurement, the lock in performs an autocalibration that measures the frequency response of analog output and input circuitry in order to compensate fo...

100 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202318
202243
202118
202021
201924
201824