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In electrical engineering, homodyne detection is a method of extracting information encoded as modulation of the phase and/or frequency of an oscillating signal, by comparing that signal with a standard oscillation that would be identical to the signal if it carried null information. "Homodyne" signifies a single frequency, in contrast to the dual frequencies employed in heterodyne detection.
When applied to processing of the reflected signal in remote sensing for topography, homodyne detection lacks the ability of heterodyne detection to determine the size of a static discontinuity in elevation between two locations. (If there is a path between the two locations with smoothly changing elevation, then homodyne detection may in principle be able to track the signal phase along the path if sampling is dense enough). Homodyne detection is more readily applicable to velocity sensing.
In optics
editIn optical interferometry, homodyne signifies that the reference radiation (i.e. the local oscillator) is derived from the same source as the signal before the modulating process. For example, in a laser scattering measurement, the laser beam is split into two parts. One is the local oscillator and the other is sent to the system to be probed. The scattered light is then mixed with the local oscillator on the detector. This arrangement has the advantage of being insensitive to fluctuations in the frequency of the laser. Usually the scattered beam will be weak, in which case the (nearly) steady component of the detector output is a good measure of the instantaneous local oscillator intensity and therefore can be used to compensate for any fluctuations in the intensity of the laser.[1][2][clarification needed]. The generated current signal from the photodetector is often too weak to measure. It is therefore converted into a voltage using a Transimpedance amplifier.
Radio technology
editIn radio technology, the distinction is not the source of the local oscillator, but the frequency used. In heterodyne detection, the local oscillator is frequency-shifted, while in homodyne detection it has the same frequency as the radiation to be detected. See direct conversion receiver.
Applications
editLock-in amplifiers are homodyne detectors integrated into measurement equipment or packaged as stand-alone laboratory equipment for sensitive detection and highly selective filtering of weak or noisy signals. Homodyne/lock-in detection has been one of the most commonly used signal processing methods across a wide range of experimental disciplines for decades.
Homodyne and heterodyne techniques are commonly used in thermoreflectance techniques.
In the processing of signals in some applications of magnetic resonance imaging, homodyne detection can offer advantages over magnitude detection. The homodyne technique can suppress excessive noise and undesired quadrature components (90° out-of-phase), and provide stable access to information that may be encoded into the phase or polarity of images.[3]
Homodyne detection was one of the key techniques in demonstrating quantum entanglement.[4] This has led to the possibility of providing a room temperature quantum sensor with continuous-variable quantum information.[5] However, challenges include reducing noise, increasing bandwidth and improving the integration of electronic and photonic components.[6] Recently, these challenges have been overcome to demonstrate a free-space-coupled room temperature quantum sensor with large-scale integrated photonics and electronics.[5]
An encrypted secure communication system can be based on quantum key distribution (QKD). An efficient receiver scheme for implementing QKD is balanced homodyne detection (BHD) using a positive–intrinsic–negative (PIN) diode.[2]
See also
editReferences
edit- ^ Chapman, Mark (2002). "Heterodyne and homodyne interferometry". Renishaw plc (UK). Archived from the original on 26 July 2017. Retrieved 14 February 2017.
- ^ a b Xu, Qing (2009). Optical Homodyne Detections and Applications in Quantum Cryptography (PDF) (Thesis). Paris: Télécom ParisTech. Retrieved 14 February 2017.
- ^ Noll, D. C.; Nishimura, D. G.; Macovski, A. (1991). "Homodyne detection in magnetic resonance imaging". IEEE Transactions on Medical Imaging. 10 (2): 154–163. doi:10.1109/42.79473. ISSN 0278-0062. PMID 18222812.
- ^ Maria Fuwa; Shuntaro Takeda; Marcin Zwierz; Howard M. Wiseman; Akira Furusawa (24 March 2015). "Experimental proof of nonlocal wavefunction collapse for a single particle using homodyne measurements". Nature Communications. 6 (6665): 6665. arXiv:1412.7790. Bibcode:2015NatCo...6E6665F. doi:10.1038/ncomms7665. PMID 25801071.
- ^ a b Gurses, Volkan; Davis, Samantha I.; Sinclair, Neil; Spiropulu, Maria; Hajimiri, Ali (13 June 2024). "Free-space quantum information platform on a chip". arXiv:2406.09158 [quant-ph].
- ^ JOEL F. TASKER; JONATHAN FRAZER; Giacomo Ferranti; JONATHAN C. F. MATTHEWS (17 May 2024). "A Bi-CMOS electronic photonic integrated circuit quantum light detector". Science Advances. 10 (20): eadk6890. arXiv:2305.08990. Bibcode:2024SciA...10K6890T. doi:10.1126/sciadv.adk6890. PMC 11100555. PMID 38758789.
External links
edit- Su, Shi-Lei; Wang, Yuan; Guo, Qi; Wang, Hong-Fu; Zhang, Shou (2012). "Generating a four-photon polarization-entangled cluster state with homodyne measurement via cross-Kerr nonlinearity". Chinese Physics B. 21 (4): 044205. Bibcode:2012ChPhB..21d4205S. doi:10.1088/1674-1056/21/4/044205. ISSN 1674-1056.