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Research & Reviews: Journal of Physics

Shot Noise for 1550 nm Laser using Balanced Homodyne Detection

Shikhar Singh

Published May 29, 2020• 0 citations
OpenAlex

Abstract

Abstract Single photon detectors are indispensable for secure communication in quantum cryptography. Shot noise, a fundamental limit to photodetection occurs due to discreteness of photons. Shot noise plays an important role in telecommunications and optical science because of its property of setting a practical limit to the signal-to-noise ratios. In order to implement BB84 protocol, there is a need to assess appropriate lower bound on experimental errors caused during secure key distribution between Alice and Bob. Shot noise limit can be measured using balanced homodyne detection. In this paper, balanced homodyne detection for measuring shot noise of 1550 nm laser has been implemented and validated. Keywords : Shot Noise, Balanced Homodyne detection, 1550nm, laser, signal Cite this Article Shikhar Singh. Shot Noise for 1550 nm Laser using Balanced Homodyne Detection. Research & Reviews: Journal of Physics . 2020; 9(1): 47–50p.

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Abstract Single photon detectors are indispensable for secure communication in quantum cryptography. Shot noise, a fundamental limit to photodetection occurs due to discreteness of photons. Shot noise plays an important role in telecommunications and optical science because of its property of setting a practical limit to the signal-to-noise ratios. In order to implement BB84 protocol, there is a need to assess appropriate lower bound on experimental errors caused during secure key distribution between Alice and Bob. Shot noise limit can be measured using balanced homodyne detection. In this paper, balanced homodyne detection for measuring shot noise of 1550 nm laser has been implemented and validated. Keywords : Shot Noise, Balanced Homodyne detection, 1550nm, laser, signal Cite this Article Shikhar Singh. Shot Noise for 1550 nm Laser using Balanced Homodyne Detection. Research & Reviews: Journal of Physics . 2020; 9(1): 47–50p.
The research of quantum noise in the interaction of laser and atoms plays a critical role in quantum optical experiments. The measurement of quantum noise is mainly based on the balanced homodyne detection method. Here, we reported a balanced homodyne detector with low noise, high gain, and high common-mode rejection ratio (CMRR) at the wavelength of 795 nm. By optimizing the selection of components and printed circuit board (PCB) layout, a minimum electronic noise of −96.7 dBm is obtained. Over the range of 1 MHz to 5 MHz, we get a flat CMRR above 59 dB and a linear gain regime, which can enable a shot noise measurement with the laser power of100 μw100~\mu \text{w}100 μw. The developed detector can be used in quantum coherent experiments with a weak probe laser of power down to tens of microwatts.
Measuring the quantum fluctuations of a laser source is the first task in performing continuous variable quantum key distribution protocols. The quantum fluctuations of the source are measured using balanced homodyne detection. In this paper, we have measured the shot noise of a pulsed laser using imperfect homodyne detection. The imperfections accounted for in the detection process are a delay between the homodyne output arms and also due to the selection of the pulse integration window larger as well as smaller than the photo-current pulse width during the analysis. We have analyzed the imperfect detection results for two different experimental layouts, and a comparative study has been performed. From our analysis, it is evident that these imperfections play a significant role in balanced homodyne detection and must be optimized properly. Our results indicate that balanced homodyne detection can be performed using limited resources, which paves the way for easy experimental realization of optical homodyne tomography and continuous variable quantum key distribution in a laboratory setting.
A balanced homodyne detection scheme with nanosecond time resolution and sub-shot-noise sensitivity has been developed and successfully tested yielding an efficient detection scheme for high-speed quantum-optical measurements and communication protocols, for example, quantum cryptography. The parameters of the detector and its precise balancing allow complete characterization of quantum states created by femtosecond light pulses that include the measurement of photon number, optical phase, and statistical properties with a high signal-to-noise ratio for the whole bandwidth from DC to several tens of megahertz. The electronic part of the detector is based on a commercially available amplifier that provides ease of construction and use while yielding good performance.
The rapid development of continuous-variable quantum communication has driven an increasing demand for high-performance quantum signal processing modules. Among these, the balanced homodyne detector (BHD) has emerged as a leading solution for practical quantum state measurement due to its capability to provide complete quantum mechanical characterization. However, its performance is often constrained by limited bandwidth and high noise levels, primarily due to the reliance on bulk optical components and discrete receiver electronics. The dominant noise source in these systems typically stems from electronic noise, while imbalances in the optical path further degrade the signal-to-noise ratio (SNR) of the BHD. In this work, we present an adjustable integrated optical path to enhance the balance within the BHD system, along with a low-noise transimpedance amplifier (TIA) by employing optoelectronic co-design. Our design achieves a bandwidth of 2.5 GHz, an input-referred noise current of only 2 pA/√Hz in 180 nm CMOS technology, and a measured quantum shot noise clearance of 15 dB generated from a 700 μA photocurrent. This is the maximum quantum shot noise clearance at the same BHD photocurrent reported to date above the GHz bandwidth.
Balanced Homodyne Detection (BHD), introduced in the 1970s, enables highly sensitive detection of phase and amplitude variations in weak light. Initially developed as an advanced optical detection technique, it rapidly became essential in quantum optics for accurately quantifying quadrature components and detecting squeezed states at the shot-noise limit. Today, BHD plays a critical role in diverse fields such as high-precision quantum metrology, gigabit speed optical communications, gravitational wave detection, and large-scale quantum information systems. In this study, a BHD simulation was implemented with a 90 phase difference between the local oscillator and the signal, thus enabling the extraction of the phase quadratureP^component of the optical field.
Abstract The time-domain balanced homodyne detector (TBHD) is critical component in continuous-variable quantum key distribution (CVQKD). The shot-noise-limited attribute of a TBHD depends on the whole spectrum of detector, in contrast to a frequency-domain balanced homodyne detector that focuses only on part of the spectrum. We propose a method for accurate calibration of the shot-noise-limited attribute of the TBHD by overlapping the gain lines of the TBHD and an integrated photodetector. The overlapping of two lines indicates that the detector is indeed shot noise limited, which is crucial to the security of CVQKD. Experimentally, we use this method to obtain a calibration error of ±1‰. Theoretical analysis showed that the CVQKD performance is very sensitive to calibration errors of shot noise, and proper countermeasures should be employed to eliminate this issue. The presented methods are expected to contribute to CVQKD security and TBHD standardization.